Influence of thermal and chemical treatment on biosorbent from rice husk and its application in removal of resorcinol from industrial wastewater

Citation: Saeed, S.; Arshad, M.Y.; Raza, A.; Mahmood, F.; Urbanowska, A.; Ahmed, A.S.; Niedzwiecki, L. Influence of Thermal and Chemical Treatment on Biosorbent from Rice Husk and Its Application in Removal of Resorcinol from Industrial Wastewater. Processes 2023,11, 3344. https://doi.org/10.3390/pr11123344 Academic Editors: George Z. Kyzas and Anna Wołowicz Received: 9 September 2023 Revised: 14 October 2023 Accepted: 28 November 2023 Published: 30 November 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). processes Article Influence of Thermal and Chemical Treatment on Biosorbent from Rice Husk and Its Application in Removal of Resorcinol from Industrial Wastewater Salaha Saeed 1, Muhammad Yousaf Arshad 1,* , Ahsan Raza 2, Faisal Mahmood 3, Agnieszka Urbanowska 4, Anam Suhail Ahmed 5and Lukasz Niedzwiecki 6,7,* 1Corporate Sustainability and Digital Chemical Management, Interloop Limited, Faisalabad 38000, Pakistan; [email protected] 2Aziz Fatimah Medical and Dental College, Faisalabad 38000, Pakistan; [email protected] 3Department of Energy System, Agriculture University Faisalabad, Faisalabad 38000, Pakistan; [email protected] 4Department of Environment Protection Engineering, Faculty of Environmental Engineering, Wroclaw University of Science and Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw, Poland; [email protected] 5Halliburton Worldwide, Houston, TX 77338, USA; [email protected] 6Department of Energy Conversion Engineering, Wroclaw University of Science and Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw, Poland 7Energy Research Centre, Centre for Energy and Environmental Technologies, VSB—Technical University of Ostrava, 17. Listopadu 2172/15, 708 00 Ostrava, Czech Republic *Correspondence: [email protected] (M.Y.A.); [email protected] (L.N.) Abstract: The removal of phenolic compounds is of great importance because of their toxic nature and potentially harmful effects on the environment and human health. This study examines the use of rice husk as a biosorbent for eliminating phenolic compounds, particularly resorcinol, from industrial wastewater. Three types of rice husk, namely raw rice husk (RRH), chemically treated rice husk (CTRH), and thermally treated rice husk (TTRH), are utilized after grinding and methanol treatment. Characterization techniques including X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and optical microscopy are used to analyze the rice husk-based adsorbents. The microscopic analysis reveals the presence of nano-pores in TTRH and the existence of carbonyl and hydroxyl groups in all sorbent samples. XRD analysis confirms the presence of silica in biosorbents. This study also examines the influence of dosage and initial concentration on resorcinol sorption. Optimized dosages of 0.5 g (RRH), 0.5 g (CTRH), and 1.5 g (TTRH) result in sorption capacities of 14 mg/g (RRH), 11 mg/g (CTRH), and 5 mg/g (TTRH). Isotherm analysis indicates that the Langmuir isotherm best describes the sorption behavior of TTRH, while the Freundlich isotherm is observed for CTRH, and both RRH and CTRH follow the Temkin isotherm. Keywords: rice husk; industrial wastewater; bio-adsorbent; phenolic compounds; optimal doses; environmental sustainability 1. Introduction Phenols are a class of chemical compounds consisting of an aromatic hydrocarbon group bounded by a hydroxyl group (-OH) directly. In organic chemistry, these compounds are also termed as phenolic. Phenol is the simplest compound of the class; it is sometimes called carbolic acid C 6 H 5 OH. Phenolic compounds are classified on the basis of the number of phenol units in the molecule, e.g., simple phenol, polyphenol, etc. These compounds are produced by plants and microorganisms with variations between species and are synthesized in industries [ 1 – 3 ]. Phenolic compounds possess a diverse range of physiological properties, including anti-allergenic, anti-atherogenic, anti-inflammatory, anti-microbial, Processes 2023,11, 3344. https://doi.org/10.3390/pr11123344 https://www.mdpi.com/journal/processes Processes 2023,11, 3344 2 of 20 antioxidant, anti-thrombotic, cardio-protective, and vasodilatory effects [ 1 – 3 ]. These compounds, found in fruits and vegetables, contribute to the antioxidant potential of foods and serve as natural sources of antioxidants [ 4 ]. They also play a significant role in the treatment and prevention of cancer, exerting chemo-preventive effects by influencing various cellular processes and signaling pathways [5,6]. Industrial development has allowed various chemicals to enter the natural environment and cause pollution. The presence of phenolic compounds in wastewater poses a threat to the environment, aquatic life, and human health and this issue must be catered to by applying an efficient treatment of wastewater [ 7 – 10 ]. Small quantities of chemicals, either naturally present in raw water or from industrial sources, or even produced during water treatment, can affect the organoleptic properties of drinking water [ 11 ]. These compounds are toxic even at very low concentrations, so it is recommended to decrease their concentration to a certain level before entering the wastewater stream. Some of the phenolic compounds were found to be remarkably harmful, such as resorcinol, etc. [ 12 – 14 ]. The anthropogenic sources of phenols are dyes, petrol, coal, chemical, fertilizer, and pharmaceutical industries [ 15 ]. It is necessary to eliminate these compounds from industrial effluents to prevent their hazardous effects and mitigate industrial wastewater pollution [ 8 , 10 , 16 ]. Resorcinol is classified as a hazardous substance and is highly combustible. Resorcinol serves as a versatile compound with various applications, including use as a coloring agent, antiseptic, disinfectant, and anti-itch agent [ 17 , 18 ]. Resorcinol is soluble in water, which poses a risk of it infiltrating waterways and harming aquatic life, making it an environmental hazard [ 19 ]. It is commonly found in the effluent waters of chemical, fertilizer, and dye industries, as well as coal conversion wastewater, contributing to water pollution [ 20 ]. It is characterized as a crystalline compound with a faint aromatic odor and a sweet taste [ 21 ]. Notably, resorcinol crystals exhibit triboluminescence, emitting light when subjected to mechanical stress [ 22 , 23 ]. Resorcinol, also known as 1,3-benzenediaol or 1,3-dihydroxybenzene, is a meta-isomer of benzene with the chemical formula C 6 H 4 (OH) 2 . It has a relative molecular mass of 110.11 [ 21 ]. The chemical structure of it is shown in Figure 1. This structure represents the two hydroxyl (-OH) groups attached to the benzene ring at the meta positions (one and three positions). Figure 1. Chemical Structure of Resorcinol [22]. A number of techniques have been developed to remove the phenolic compounds from an aqueous solution including chlorination, solvent extraction, liquid membrane permeation, coagulation, chemical oxidation, and adsorption, etc. [ 24 ]. Among all these methods, adsorption is the most economical, effective, and simple method [ 16 ]. There are a number of techniques used for the removal of phenolic compounds from water. These techniques are divided into three main categories i.e., biological treatment, chemical treatment, and physical treatment [25]. Conventionally, biological treatment, activated carbon adsorption, and solvent extraction techniques are used. The physical adsorption technique is often thought to be the best, most viable, and frequently utilized strategy, which requires minimal effort, for the expulsion of phenolic compounds. Adsorption is a well-known separation process [ 26 , 27 ], Processes 2023,11, 3344 3 of 20 which has a multitude of different applications, such as wastewater treatment, water desalination [ 28 ], pressure swing adsorption for the separation of gases [ 29 , 30 ], carbon capture and use [ 31 ], or production of cold in adsorption chillers [ 27 , 32 ], just to name a few. Adsorption has been found to be superior to other techniques for water reuse because of its low initial cost, flexibility and simplicity of design, ease of operation, and insensitivity to toxic pollutants [33]. The most popular and widely used adsorbent material for the treatment of wastewater is activated carbon [ 34 , 35 ]. Activated carbon present in powdered or granular form has a porous structure; these interconnected pores increase the surface area of carbon, thus making it the best adsorbent. But despite its great benefits, activated carbon is costly: the chemical and thermal regeneration of spent carbon is expensive, impractical on a large scale, produces additional effluent, and results in a considerable loss of the adsorbent [ 33 ]. So instead of this, there are many low-cost agricultural by-products that can be used as adsorbents for the treatment of wastewater. They include banana peel, orange peel, wheat straw, sawdust, powdered waste sludge, wheat shells, wheat bran, and hen feathers [ 9 , 33 ]. The purpose of our work is to investigate the efficiency of rice husk as an adsorbent for the removal of phenolic compounds from industrial wastewater. Rice husk is an abundant and low-cost agricultural waste residue and is easily available in large quantities. The effects of various operating parameters on adsorption such as sorbent dosage and contact time were monitored and optimal experimental conditions were determined [ 36 , 37 ]. Different adsorption isotherms (Langmuir and Freundlich isotherms) were used to find out the most suitable models describing our experimental findings. The nature of the substances and solution being studied is another factor to consider. Different adsorbates may have different chemical properties, such as polarity or molecular size, which can influence the adsorption process. Likewise, the characteristics of the solution, such as its pH or the presence of other ions, can also affect the adsorption behavior and the choice of the appropriate isotherm model [38,39]. 2. Materials and Methods 2.1. Experimental Setup For the experimentation, commercially available powdered rice husk was sieved using meshes ranging from 200 to 400 µ m, and an average size was selected for the study. The sieved material was thoroughly washed with doubly deionized distilled water to remove fine particles and impurities. Three different methods were employed to treat the rice husk during the experimentation. Initially, the rice husk was washed and dried in an oven for 4 h to eliminate moisture. A portion of the dried rice husk was carefully stored in bottles to maintain its dry state and prevent moisture reabsorption [40,41]. During the experimentation, various equipment was utilized to facilitate the procedures and ensure accurate results. The weighing balance (Sartorius-TE214S, Cole Parmer, Goettingen, Germany) played a crucial role in precisely measuring the adsorbate and adsorbents. The jar test operator (Armfield WI-A, Cole Parmer) was employed for coagulation purposes, aiding in the treatment process. To analyze the phenolic compounds, a UV spectrophotometer (Shimadzu UV-1800, Cole Parmer) was utilized, enabling accurate and reliable measurements. Measuring cylinders were used for the preparation of samples, ensuring the appropriate volume for each experiment. Whatman Filter papers were employed for the filtration of samples, removing impurities, and facilitating the analysis. The sieve, categorized by the US standard mesh, enabled the sieve analysis of adsorbents, providing valuable information about their particle size distribution. The distiller (FAVORIT W4L, Cole Parmer) played a vital role in the distillation of water, ensuring its purity for the experiments. Additionally, a de-ionizer (Cole Parmer) was used to remove ions from the water, further enhancing its quality. Processes 2023,11, 3344 4 of 20 2.2. Experimental Methods Adsorption isotherms are mathematical models used to describe the relationship between the concentration of adsorbate molecules in a solution and the amount of adsorbate adsorbed onto a solid adsorbent. Three commonly used types of adsorption isotherms are the Langmuir isotherm (Equation (1)), the Freundlich isotherm (Equation (4)), and the Temkin isotherm (Equation (7)) [ 42 ]. The Langmuir adsorption isotherm, developed by Langmuir, describes the adsorption of gases onto solid surfaces. It assumes a dynamic equilibrium between adsorbed and free gaseous molecules. Originally devised for gas– solid adsorption on activated carbon, it has been used to assess and compare various bio-sorbents. Langmuir’s theory links the decline of intermolecular attractive forces to increasing distance [43]. q=qmKads ×C 1+Kads ×C(1) where qe—sorbed concentration (adsorption density) (mg/g), qm—maximum capacity of adsorbent for adsorbate, C—equilibrium concentration (mg/L), Kads—measure of affinity of adsorbate for adsorbent. Linear form of Langmuir model [23] can be given by Ce qe =Ce qm +1 qm×Kads (2) Ce Cads =1 Qb +Ce Q(3) The Freundlich isotherm is an empirical equation describing the isothermal variation of gas adsorption per unit mass of solid adsorbent with pressure. It is the earliest relationship for non-ideal and reversible adsorption, applicable to both monolayer and multilayer adsorption. It accommodates the non-uniform distribution of adsorption heat and affinities on heterogeneous surfaces. This isotherm is widely used in heterogeneous systems, particularly for organic compounds or highly interactive species on activated carbon and molecular sieves [43]. Empirical equation is given by q=Kf×C1 n(4) where Kf—empirical Freundlich constant (L/g), 1/n—Freundlich exponent. Linear form of Freundlich isotherm [23] is given by logqe=logKf+1 nlog Ce (5) or log Cads =logCm+1 nlogCe(6) Temkin isotherm is the early model describing the adsorption of hydrogen onto platinum electrodes within the acidic solutions. The isotherm contains a factor that explicitly take into account the adsorbent–adsorbate interactions. By ignoring the extremely low and large value of concentrations, the model assumes that heat of adsorption (function of temperature) of all molecules in the layer would decrease linearly rather than logarithmic with coverage [43,44]. Its empirical equation is given by qe=RT blog(A∗Ce)(7) Processes 2023,11, 3344 5 of 20 Its linear form is qe=Blog(A)+Blog(Ce)(8) where A = Temkin constant at equilibrium (L/g), B = RT b= constant related to heat of sorption. The selection of isotherms in adsorption studies depends on a range of factors. One important factor is the concentration of the adsorbate in the solution [ 40 ]. Different isotherm models may be more suitable for low or high concentration data ranges, and the choice of isotherm can affect the accuracy of the adsorption data. In Figure 2, the methodology employed in this study, aimed at determining the optimum conditions for the adsorption process, is explained. Two key parameters, namely concentration and adsorbent dose, were investigated to identify the optimal values. The concentration of the phenolic compounds in the wastewater was varied to assess its impact on the adsorption efficiency. Different concentrations were evaluated to determine the optimum level that yielded the highest removal of phenolic compounds. Similarly, the adsorbent dose, representing the amount of rice husk used in the adsorption process, was studied to determine the ideal dosage for maximum adsorption efficiency. Various doses of the three types of rice husk (raw, chemically treated, and thermally treated) were evaluated to identify the optimal amount that resulted in the highest removal of phenolic compounds. The removal efficiency can be calculated using the following formulation: Removal e f f iciency =(initial concentration −f inal concentration) initial concentration (9) Furthermore, adsorption isotherms were employed to investigate the relationship between the adsorbate and adsorbent. The Langmuir isotherm, a monolayer adsorption model, has been utilized to determine the maximum adsorption capacity and the equilibrium constant for the adsorption process. The Freundlich isotherm, representing multilayer adsorption, has been used to understand the adsorption behavior in heterogeneous systems. Lastly, the Temkin isotherm, which considers the effects of heat and adsorbent-adsorbate interactions, has been applied to evaluate the energy changes during adsorption. Figure 2. Experimental Methodology. 2.3. Preparation of Adsorbents and Adsorbate Rice husks, the protective coatings of grains and seeds, consist of hard materials such as “opaline silica” and “lignin” that provide resilience during the growth period [ 23 , 41 ]. Due to its abundance and low cost, rice husk is currently being explored as a promising biomass. It contains cellulose, hemicellulose, and lignin as the main organic compounds [ 45 ]. This composition endows rice husk with excellent adsorbent properties, making it a promising candidate for pollutant removal applications [41,46]. In order to enhance the sorption properties of the rice husk, a series of treatment methods were applied. Initially, 200 g of dried rice husk underwent chemical treatment using 0.1 M nitric acid for 1 h, followed by a 4 h soak in methanol. This chemical treatment Processes 2023,11, 3344 6 of 20 aimed to remove both organic and inorganic matter from the surface of the rice husk, thereby improving its sorption capabilities. Subsequently, 100 g of the chemically treated rice husk underwent thermal treatment. The husk was placed in a closed muffle furnace and exposed to a temperature of 400 ◦ C for 1 h, resulting in a significant increase in its surface area. The resulting ash from the thermal treatment was utilized as the sorbent material in the study. These treatment methods yielded three distinct types of rice husk: raw or untreated rice husk, chemically treated rice husk, and thermally treated rice husk, each possessing unique properties for the subsequent sorption experiments. Mainly, the current research study focused on the adsorption of phenolic compounds, specifically Resorcinol. Initially, a solution containing all phenolic compounds was prepared by thoroughly mixing them with 1000 mL of distilled deionized water. A flask was used to hold 0.1 g of the phenolic compounds, along with a portion of the water, which was then stirred using a magnetic stirrer. Gradually, the remaining water was added to the flask to create a 100 ppm solution. To enhance solubility, methanol and NaOH were introduced. From this stock solution, additional dilutions with desired concentrations (1, 3, 5, and 7 ppm) were prepared in 100 mL volumes. These dilutions were carefully selected to achieve the targeted concentrations for the experimental procedure. 2.4. Effect of Dose and Initial Concentration To assess the impact of dosage on the removal efficiency of rice husk, the study employed four different doses of raw, chemically treated, and thermally treated rice husk. The sorbent doses, weighing 0.5 g, 1 g, 1.5 g, and 2 g, were accurately measured using a weighing balance. The prepared doses were placed in plastic bottles, each containing the same concentration. These bottles were then secured in a thermostatic shaker, set to operate at a speed of one hundred revolutions per minute (RPM), for a duration of 30 min. This process was repeated sequentially for raw rice husk, chemically treated rice husk, and, finally, thermally treated rice husk. Each type of rice husk dose was placed in separate bottles and subjected to the shaker treatment. Subsequently, the samples were filtered using Whatman filter paper no. 40 to separate the solid sorbent from the liquid solution. The filtered samples were then injected back into the respective bottles. To create a stock solution with a concentration of 1 ppm, 1 mL of the solute was dissolved in 9 mL of solvent, and this solution was prepared in a separate bottle. The solutions, including the stock solution and the filtered samples, were analyzed using a UV spectrophotometer, utilizing a specific wavelength, to determine the removal efficiency of the rice husk sorbents. By following this experimental procedure, this study aimed to evaluate the influence of varying dosage on the effectiveness of raw, chemically treated, and thermally treated rice husk as sorbents. This study involved the preparation of sorbent doses weighing 1 g each of raw, chemically treated, and thermally treated rice husk. Accurate measurements were taken using a weighing balance. These doses were then placed in plastic bottles containing adsorbate solutions of varying concentrations (1, 3, 5, and 7 ppm). To ensure consistent conditions, the bottles with the sorbent doses and adsorbate solutions were placed in a thermostatic shaker operating at 100 RPM for 30 min. This process was repeated for each type of rice husk sorbent, with the raw rice husk doses being used first, followed by the chemically treated and thermally treated rice husk doses. Subsequently, the samples were filtered using Whatman filter paper no. 40 to separate the solid sorbent from the liquid solution. After filtration, the filtered samples were returned to their respective bottles for further analysis. Additionally, a stock solution of 1 ppm concentration was prepared by dissolving 1 mL of the solute in 9 mL of solvent, and this stock solution was also placed in a plastic bottle for analysis. All solutions, including the filtered samples and the stock solution, underwent analysis using a UV spectrophotometer at a specific wavelength [23]. Processes 2023,11, 3344 7 of 20 2.5. Adsorption Isotherms The adsorption isotherms provide valuable insights into the relationship between the concentration of the sorbate and its accumulation on the surface of the sorbent at a constant temperature [ 23 ]. To determine the maximum adsorption capacities of the adsorbents, experiments were conducted by varying the concentrations while keeping all other parameters constant. To study the isotherms, dilutions of 10, 20, and 30 ppm were prepared for raw rice husk, 10, 15, and 25 ppm for chemically treated rice husk, and 10, 15, 25, and 30 ppm for thermally treated rice husk. The optimum conditions determined for raw, chemically treated, and thermally treated rice husk were then applied in the experiments. In order to characterize the adsorbent materials, optical microscopy, Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) techniques were employed. These analyses provided valuable information on pore sizes, surface properties, and functional groups present in the rice husk, which play a crucial role in the adsorption process. 3. Results and Discussion The main objective of this study was to determine the adsorption capacity of rice husks for the removal of phenolic compounds from solution. In order to investigate the sorption capabilities of rice husk, a series of experiments were conducted to optimize various parameters, including the sorbent dose and the initial concentration of the phenolic compound. By performing these experiments and analyzing the resulting isotherms, valuable insights into the adsorption behavior of rice husk and its effectiveness as an adsorbent were obtained. The adsorption kinetics were also investigated. 3.1. Characterization of Rice Husk Samples Optical microscopy analysis was employed to gain valuable insights into the sizes of microor nanopores in the rice husk samples. The characterization of rice husk involved the use of three different techniques, and the results obtained are presented below in Figure 3a. In the case of both raw rice husk and chemically treated rice husk, a magnification of 5 × was found to be more suitable (Figure 3a,b). For the analysis of thermally treated rice husk, an optimal magnification of 10 × was determined in Figure 3c. Microscopic images show that the structure has been altered as a result of thermal treatment. On the other hand, the morphology of the chemically treated sample was similar to the raw sample, indicating that chemical treatment mostly influenced the surfaces from the perspective of functional groups (Figure 3d). FTIR analysis identifies the chemical compounds present in consumer products, polymers, and in pharmaceutical products. It offers the quantitative and qualitative analysis of organic compounds. The FTIR analysis shown in the Figure 3d allowed the clear identification of OH, C=O, and C-OH functional groups. The OH group is typical for many different types of biomass, as it is relatively abundant in cellulose and hemicellulose [47]. The C=O group at 1725 cm −1 was also found by Wawrzkiewicz and Podko´scielna [ 48 ] during studies on the sorption of auramine O basic dye using ethylene glycol dimethylacrylatebased microspheres. Electrostatic interaction between the dye molecule and the C=O functional group present at the surface of the microspheres has been proposed by Wawrzkiewicz and Podko´scielna [ 48 ] as a part of the mechanism of interactions between the sorbent and the dye. Processes 2023,11, 3344 8 of 20 Figure 3. Chemically treated, raw materials and thermally treated samples using Optical Microscopy, results at (a) 5×, (b) 5×, (c) 10×, (d) FTIR Results. XRD is a unique method used in determining the crystalline property of a compound. It is used for the characterization of various materials. XRD analysis shows that SiO 2 and Fe 3 O 4 are major constituents that will monitor the adsorption phenomenon. The XRD analysis of raw, chemically treated, and thermally treated rice husk in Figure 4a–c revealed important structural changes induced by the treatment processes. The XRD patterns confirmed the presence of major constituents, SiO 2 (silicon dioxide) and Fe 3 O 4 (iron (II, III) oxide), which are crucial for monitoring the adsorption phenomenon. Chemical treatment led to the degradation or removal of cellulose, hemicellulose, and lignin, resulting in changes in the XRD pattern and the formation of new phases. Thermal treatment further modified the XRD pattern, with significant degradation of the aforementioned components and the emergence of new peaks. These structural modifications, along with the presence of SiO 2 and Fe 3 O 4 , highlight the potential influence of the treatments on the adsorption capabilities of rice husk, emphasizing the need for further investigation into their role in phenolic compound removal. Processes 2023,11, 3344 9 of 20 Figure 4. The XRD results for RRH (a), for CTRH (b), for TTRH (c). Based on the experimental data, descriptive statistics and correlation analysis were conducted to explore the relationships and characteristics of the variables. Descriptive statistics provided insights into the central tendency and variability of the data, including mean, standard deviation, minimum, maximum, and quartiles for each variable within each group (Raw Rice Husk, Chemically Treated Rice Husk, Thermally Treated Rice Husk). The correlation analysis calculated correlation coefficients between the variables (m,q e , 1/q e ,C e /q e , 1/C e , log(q e ), ln(C e )) within each group, helping to identify relationships or Processes 2023,11, 3344 16 of 20 resorcinol. The optimized doses for RH (raw rice husk), CRH (chemically treated rice husk), and TRH (thermally treated rice husk) were found to be 0.5 g, 0.5 g, and 1.5 g, respectively. The CRH and TRH gave a maximum removal efficiency of about 80% when the effect of dose was studied. When the effect of concentration was studied, the maximum removal efficiency was found in RH, above, i.e., 90%. The sorption capacity for RH, CRH, and TRH was found to be 14 mg/g, 11 mg/g, and 5 mg/g, respectively. The Langmuir isotherm performed better than the Freundlich and Temkin isotherms in terms of the quality of fit to the experimental data. Author Contributions: M.Y.A. (Conceptualization, Methodology, Software, Validation, Investigation, Resources, Writing—Original Draft, Supervision, Project Administration); S.S. (Methodology, Formal Analysis, and Writing—Original Draft); A.S.A. (Software, Validation, Writing—Review and Editing); L.N. (Writing—Review and Editing, Visualization); A.R. (Validation, Investigation, Writing—Review and Editing); F.M. (Investigation, Writing—Review and Editing); A.U. (Investigation, Writing—Original Draft, Visualization). All authors have read and agreed to the published version of the manuscript. Funding: This research received no external funding. Data Availability Statement: Data available on request. Conflicts of Interest: Salaha Saeed and Muhammad Yousaf Arshad were employed by the company Interloop Limited. Anum Suhail Ahmad was employed by the company Halliburton Worldwide. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Appendix A Table A1. Co-relation analysis using Heat-Map (Python Programming Software: Perkin Elmer software version 10.4.3, XRD 5.20 Mavern Paranyltical). Raw Rice Husk Co-Relation Matrix-Variables M Qe1/qeCe/qe1/Celog(qe) ln(Ce) m 1 0.9642 −0.9746 0.6457 −0.6652 −0.9883 −0.9831 qe0.9642 1 −0.9983 0.6027 −0.6337 −0.9928 −0.9876 1/qe−0.9746 −0.9983 1 −0.5909 0.6172 0.994 0.9889 Ce/qe0.6457 0.627 −0.5909 1 −0.9965 −0.6346 −0.5781 1/Ce−0.6652 −0.6337 0.6172 −0.9965 1 0.6402 0.5855 log(qe)−0.9883 −0.9928 0.994 −0.6346 0.6402 1 0.9942 ln(Ce)−0.9831 −0.9876 0.9889 −0.5781 0.5855 0.9942 1 Chemically Treated Rice Husk M 1 0.9962 −0.999 0.6641 −0.6732 −0.9983 −0.9933 Qe0.9962 1 −0.9972 0.6315 −0.6554 −0.999 −0.9941 1/qe−0.999 −0.9972 1 −0.6383 0.6682 0.9974 0.9925 Ce/qe0.6641 0.6315 −0.6383 1 −0.9951 −0.6624 −0.5866 1/Ce−0.6732 −0.6554 0.6682 −0.9951 1 0.6624 0.6247 log(qe)−0.9983 −0.999 0.9974 −0.6224 0.6624 1 0.9947 ln(Ce)−0.9933 −0.9941 0.9925 −0.5866 0.6247 0.9947 1 Thermally Treated Rice Husk M 1 0.9971 −0.9949 0.6401 −0.6652 −0.996 −0.9893 Qe0.9971 1 −0.9953 0.6278 −0.6524 −0.998 −0.9917 1/qe−0.9949 −0.9953 1 −0.6343 0.6579 0.9954 0.9884 Ce/qe0.6401 0.6278 −0.6343 1 −0.9974 −0.6272 −0.5902 1/Ce−0.6652 −0.6524 0.6579 −0.9974 1 0.6595 0.6218 log(qe)−0.9966 −0.998 0.9954 −0.6272 0.6595 1 0.9921 ln(Ce)−0.9893 −0.9917 0.9884 −0.5902 0.6218 0.9921 1 Processes 2023,11, 3344 17 of 20 Table A2. Multi-polynomial regression analysis. Raw Rice Husk Coefficients Estimate Std. Error tValue Pr(>|t|) Intercept 0.02706 0.04325 0.626 0.581 M 0.22909 0.04095 5.595 0.021 Qe−0.05373 0.01138 −4.719 0.033 1/qe−0.02438 0.04391 −0.55 0.611 Ce/qe−0.1116 0.05321 −2.097 0.169 1/Ce−0.05311 0.05734 −0.925 0.4 log(qe)−0.11594 0.02677 −4.328 0.043 Chemically Treated Rice Husk Intercept 0.0482 0.05511 0.875 0.46 M 0.19237 0.04361 4.413 0.047 Qe−0.06816 0.01491 −4.577 0.041 1/qe−0.05864 0.05911 −0.992 0.422 Ce/qe−0.06108 0.07124 −0.858 0.468 1/Ce−0.05673 0.07916 −0.717 0.539 log(qe)−0.12815 0.03683 −3.477 0.079 Thermally Treated Rice Husk Coefficients Estimate Std. Error tValue Pr(>|t|) Intercept −0.07946 0.08486 −0.937 0.42 M 0.13906 0.0667 2.094 0.211 Qe−0.1607 0.02348 −6.847 0.012 1/qe0.00525 0.09154 0.057 0.955 Ce/qe0.02137 0.11073 0.193 0.868 1/Ce−0.00233 0.12309 −0.019 0.986 log(qe)−0.24181 0.05725 −4.224 0.052 Table A3. Effect of dose and concentration on removal efficiency. Dose (g) RE% Raw Chemical Thermal 0.5 55.16526406 78.14368 46.18855958 1 46.77399683 80.77814 63.84924991 1.5 20.13660202 82.19295 76.241005 2 38.62666179 75.26528 76.28979144 Concentration (ppm) RE% Raw Chemical Thermal 1 86.61972 26.86913 76.77766 3 79.43662 52.98207 87.01061 5 83.6338 69.96707 97.89243 7 98.92019 76.58251 94.12123 Table A4. Data for isotherms. CpCiCiCeCelog Ce Ci–CeV (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (L) Raw Rice Husk 10 10 1 5.465839 0.54658 −0.2623 0.45342 0.1 20 20 2 12.43781 1.24378 0.09474 0.75622 0.1 30 30 3 20.84317 2.08432 0.31896 0.91568 0.1 Processes 2023,11, 3344 18 of 20 Table A4. Cont. CpCiCiCeCelog Ce Ci–CeV (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (L) Chemically Treated Rice Husk 10 10 1 7.36 0.736 −0.13312 0.264 0.1 15 15 1.5 11.36 1.136 0.055378 0.364 0.1 25 25 2.5 19.95842 1.995842 0.300126 0.504158 0.1 Thermally Treated Rice Husk 10 10 1 8.125 0.8125 −0.09018 0.1875 0.1 15 15 1.5 12.365 1.2365 0.092194 0.2635 0.1 25 25 2.5 20.27027 2.027027 0.30686 0.472973 0.1 30 30 3 23.654 2.3654 0.373905 0.6346 0.1 Table A5. Dosage data-treatment analysis. Mqe1/qeCe/qe1/CeLog qeLn Ce (g) Raw Rice Husk 0.5 0.09068 11.0274 6.0274 1.82955 −1.04247 −0.60407 0.5 0.15124 6.61184 8.22368 0.804 −0.82032 0.218156 0.5 0.18314 5.46041 11.3812 0.47977 −0.73722 0.734441 Chemically Treated Rice Husk 0.5 0.0528 18.93939 13.93939 1.358696 −1.27737 −0.30653 0.5 0.0728 13.73626 15.6044 0.880282 −1.13787 0.127513 0.5 0.100832 9.917526 19.79381 0.501042 −0.9964 0.691066 Thermally Treated Rice Husk 1.5 0.0125 80 65 1.230769 −1.90309 −0.20764 1.5 0.017567 56.926 70.38899 0.808734 −1.75531 0.212285 1.5 0.031532 31.71429 64.28571 0.493333 −1.50125 0.70657 s1.5 0.042307 23.63694 55.91081 0.422761 −1.37359 0.860947 References 1. Balasundram, N.; Sundram, K.; Samman, S. Phenolic compounds in plants and agri-industrial by-products: Antioxidant activity, occurrence, and potential uses. Food Chem. 2006,99, 191–203. [CrossRef] 2. Muhammad Yousaf Arshad, A.R. Integrating Circular Economy, SBTI, Digital LCA, and ESG Benchmarks for Sustainable Textile Dyeing: A Critical Review of Industrial Textile Practices. Glob. NEST J. 2023,24, 29–51. [CrossRef] 3. Arshad, M.Y.; Saeed, S.; Raza, A.; Ahmad, A.S.; Urbanowska, A.; Jackowski, M.; Niedzwiecki, L. Integrating Life Cycle Assessment and Machine Learning to Enhance Black Soldier Fly Larvae-Based Composting of Kitchen Waste. Sustainability 2023 ,15, 12475. [CrossRef] 4. Kermani, M.; Gholami, M.; Gholizade, A.; Farzadkia, M.; Esrafili, A. Effectiveness of Rice Husk Ash in Removal of Phenolic Compounds from Aqueous Solutions, Equilibrium and Kinetics Studies. Iran. J. Health Environ. 2012,5, 9–23. 5. Huang, W.Y.; Cai, Y.Z.; Zhang, Y. Natural phenolic compounds from medicinal herbs and dietary plants: Potential use for cancer prevention. Nutr. Cancer 2010,62, 1–20. [CrossRef] [PubMed] 6. Leng, L.; Yuan, X.; Zeng, G.; Shao, J.; Chen, X.; Wu, Z.; Wang, H.; Peng, X. Surface characterization of rice husk bio-char produced by liquefaction and application for cationic dye (Malachite green) adsorption. Fuel 2015,155, 77–85. [CrossRef] 7. Daniel, O.; Meier, M.S.; Schlatter, J.; Frischknecht, P. Selected phenolic compounds in cultivated plants: Ecologic functions, health implications, and modulation by pesticides. Environ. Health Perspect. 1999,107, 109–114. [PubMed] 8. Rafique, M.; Kiran, S.; Ashraf, A.; Mukhtar, N.; Rizwan, S.; Ashraf, M.; Arshad, M. Effective removal of direct orange 26 dye using copper nanoparticles synthesized from Tilapia fish scales. Glob. NEST J. 2022,24, 311–317. 9. Arshad, Y.; Rashid, A.; Gul, H.; Ahmad, A.; Jabbar, F. Optimization of acid-assisted extraction of pectin from banana (Musa acuminata) peels by central composite design. Glob. NEST J. 2022,24, 752–756. 10. Yar, A.; Arshad, M.Y.; Asghar, F.; Amjad, W.; Asghar, F.; Hussain, M.I.; Lee, G.H.; Mahmood, F. Machine Learning-Based Relative Performance Analysis of Monocrystalline and Polycrystalline Grid-Tied PV Systems. Int. J. Photoenergy 2022 ,2022, 3186378. [CrossRef] Processes 2023,11, 3344 19 of 20 11. Ramos, R.L.; Moreira, V.R.; Lebron, Y.A.; Santos, A.V.; Santos, L.V.; Amaral, M.C. Phenolic compounds seasonal occurrence and risk assessment in surface and treated waters in Minas Gerais—Brazil. Environ. Pollut. 2021,268, 115782. [CrossRef] 12. Hollman, P.; Katan, M. Absorption, metabolism and health effects of dietary flavonoids in man. Biomed. Pharmacother. 1997 ,51, 305–310. [CrossRef] [PubMed] 13. Arshad, M.Y.; Rashid, A.; Mahmood, F.; Saeed, S.; Ahmed, A.S. Metal (II) triazole complexes: Synthesis, biological evaluation, and analytical characterization using machine learning-based validation. Eur. J. Chem. 2023,14, 155–164. [CrossRef] 14. Rafique, M.A.; Kiran, S.; Jamal, A.; Anjum, M.N.; Jalal, F.; Munir, B.; Hafiz, I.; Noureen, F.; Ajmal, S.; Ahmad, W.; et al. Green synthesis of copper nanoparticles using Allium cepa (onion) peels for removal of Disperse Yellow 3 dye. Desalin. Water Treat. 2022,272, 259–265. [CrossRef] 15. Michałowicz, J.; Duda, W. Phenols—Sources and toxicity. Pol. J. Environ. Stud. 2007,16, 347–362. 16. Raza, W.; Lee, J.; Raza, N.; Luo, Y.; Kim, K.-H.; Yang, J. Removal of phenolic compounds from industrial waste water based on membrane-based technologies. J. Ind. Eng. Chem. 2019,71, 1–18. [CrossRef] 17. Zhou, M.; Zhang, J.; Sun, C. Occurrence, ecological and human health risks, and seasonal variations of phenolic compounds in surface water and sediment of a potential polluted river basin in China. Int. J. Environ. Res. Public Health 2017 ,14, 1140. [CrossRef] [PubMed] 18. Saeed, M.A.; Niedzwiecki, L.; Arshad, M.Y.; Skrinsky, J.; Andrews, G.E.; Phylaktou, H.N. Combustion and Explosion Characteristics of Pulverised Wood, Valorized with Mild Pyrolysis in Pilot Scale Installation, Using the Modified ISO 1 m3 Dust Explosion Vessel. Appl. Sci. 2022,12, 12928. [CrossRef] 19. Morton, L.W.; Caccetta, R.A.A.; Puddey, I.B.; Croft, K.D. Chemistry and biological effects of dietary phenolic compounds: Relevance to cardiovascular disease. Clin. Exp. Pharmacol. Physiol. 2000,27, 152–159. [CrossRef] 20. Mainali, K. Phenolic compounds contaminants in water: A Glance. Curr. Trends Civ. Struct. Eng. 2020,4. [CrossRef] 21. Hahn, S. Resorcinol; World Health Organization: Geneva, Switzerland, 2006. 22. Durairaj, R.B. Resorcinol: Chemistry, Technology and Applications; Springer Science & Business Media: Berlin/Heidelberg, Germany, 2005. 23. Akhtar, M.; Bhanger, M.; Iqbal, S.; Hasany, S.M. Sorption potential of rice husk for the removal of 2, 4-dichlorophenol from aqueous solutions: Kinetic and thermodynamic investigations. J. Hazard. Mater. 2006,128, 44–52. [CrossRef] 24. Anku, W.W.; Mamo, M.A.; Govender, P.P. Phenolic compounds in water: Sources, reactivity, toxicity and treatment methods. In Phenolic Compounds-Natural Sources, Importance and Applications; BoD–Books on Demand: Norderstedt, Germany, 2017; pp. 419–443. 25. Achak, M.; Hafidi, A.; Ouazzani, N.; Sayadi, S.; Mandi, L. Low cost biosorbent “banana peel” for the removal of phenolic compounds from olive mill wastewater: Kinetic and equilibrium studies. J. Hazard. Mater. 2009,166, 117–125. [CrossRef] 26. Jodłowski, P.J.; Dymek, K.; Kurowski, G.; Hyjek, K.; Boguszewska-Czubara, A.; Budzy´nska, B.; Pajdak, A.; Kuterasi´nski, Ł.; Piskorz, W.; Jele´n, P.; et al. In vivo and in vitro studies of efficient mephedrone adsorption over zirconium-based metal-organic frameworks corroborated by DFT+D modeling. Microporous Mesoporous Mater. 2023,359, 112647. [CrossRef] 27. Sowa, M.; Sztekler, K.; Mlonka-M˛edrala, A.; Mika, Ł. An Overview of Developments In Silica Gel Matrix Composite Sorbents for Adsorption Chillers with Desalination Function. Energies 2023,16, 5808. [CrossRef] 28. Pajdak, A.; Kulakowska, A.; Liu, J.; Berent, K.; Kudasik, M.; Krzywanski, J.; Kalawa, W.; Sztekler, K.; Skoczylas, N. Accumulation and Emission of Water Vapor by Silica Gel Enriched with Carbon Nanotubes CNT-Potential Applications in Adsorption Cooling and Desalination Technology. Appl. Sci. 2022,12, 5644. [CrossRef] 29. Qasem, N.A.A.; Ben-Mansour, R. Assessment of Appropriate Geometry for Thermally Efficient CO 2 Adsorption Beds. Appl. Sci. 2022,12, 5726. [CrossRef] 30. Gallucci, K.; Taglieri, L.; Papa, A.A.; Di Lauro, F.; Ahmad, Z.; Gallifuoco, A. Non-Energy Valorization of Residual Biomasses via HTC: CO2Capture onto Activated Hydrochars. Appl. Sci. 2020,10, 1879. [CrossRef] 31. Bieniek, A.; Sun, S.; Jerzak, W.; Wu, C.; Magdziarz, A. Thermodynamic modelling of integrated carbon capture and utilisation process with CaO-based sorbents in a fixed-bed reactor. J. Environ. Manag. 2023,343, 118201. [CrossRef] 32. Kalawa, W.; Sztekler, K.; Mlonka-M˛edrala, A.; Radomska, E.; Nowak, W.; Mika, Ł.; Bujok, T.; Boruta, P. Simulation Analysis of Mechanical Fluidized Bed in Adsorption Chillers. Energies 2023,16, 5817. [CrossRef] 33. Aksu, Z.; Yener, J. A comparative adsorption/biosorption study of mono-chlorinated phenols onto various sorbents. Waste Manag. 2001,21, 695–702. [CrossRef] 34. Bertin, L.; Berselli, S.; Fava, F.; Petrangeli-Papini, M.; Marchetti, L. Anaerobic digestion of olive mill wastewaters in biofilm reactors packed with granular activated carbon and “Manville” silica beads. Water Res. 2004,38, 3167–3178. [CrossRef] 35. Bertin, L.; Lampis, S.; Todaro, D.; Scoma, A.; Vallini, G.; Marchetti, L.; Majone, M.; Fava, F. Anaerobic acidogenic digestion of olive mill wastewaters in biofilm reactors packed with ceramic filters or granular activated carbon. Water Res. 2010 ,44, 4537–4549. [CrossRef] 36. Shubham, K.; Srivastav, S. Medicinal Chemistry & Analysis. Adsorption 2018,3, 4. 37. Kajjumba, G.W.; Emik, S.; Öngen, A.; Özcan, H.K.; Aydın, S. Modelling of adsorption kinetic processes—Errors, theory and application. In Advanced Sorption Process Applications; BoD—Books on Demand: Norderstedt, Germany, 2018; pp. 1–19. 38. Al-Ghouti, M.A.; Da’ana, D.A. Guidelines for the use and interpretation of adsorption isotherm models: A review. J. Hazard. Mater. 2020,393, 122383. [CrossRef] [PubMed] Processes 2023,11, 3344 20 of 20 39. Wang, J.; Guo, X. Adsorption isotherm models: Classification, physical meaning, application and solving method. Chemosphere 2020,258, 127279. [CrossRef] [PubMed] 40. Ayawei, N.; Ebelegi, A.N.; Wankasi, D. Modelling and interpretation of adsorption isotherms. J. Chem. 2017 ,2017, 3039817. [CrossRef] 41. Ahmaruzzaman, M.; Gupta, V.K. Rice husk and its ash as low-cost adsorbents in water and wastewater treatment. Ind. Eng. Chem. Res. 2011,50, 13589–13613. [CrossRef] 42. Ba¸sar, C.A. Applicability of the various adsorption models of three dyes adsorption onto activated carbon prepared waste apricot. J. Hazard. Mater. 2006,135, 232–241. [CrossRef] [PubMed] 43. Foo, K.; Hameed, B. Insights into the modeling of adsorption isotherm systems. Chem. Eng. J. 2010,156, 2–10. [CrossRef] 44. ˇ Cespiva, J.; Jadlovec, M.; Výtisk, J.; Serenˇcíšová, J.; Tadeáš, O.; Honus, S. Softwood and Solid Recovered Fuel Gasification Residual Chars as Sorbents for Flue Gas Mercury Capture. Environ. Technol. Innov. 2023,29, 102970. [CrossRef] 45. Syuhadah, N.; Rohasliney, H. Rice husk as biosorbent: A review. Health Environ. J. 2012,3, 89–95. 46. Teng, H.; Wei, Y.-C. Thermogravimetric studies on the kinetics of rice hull pyrolysis and the influence of water treatment. Ind. Eng. Chem. Res. 1998,37, 3806–3811. [CrossRef] 47. Pawlak-Kruczek, H.; Arora, A.; Gupta, A.; Saeed, M.A.; Niedzwiecki, L.; Andrews, G.; Phylaktou, H.; Gibbs, B.; Newlaczyl, A.; Livesey, P.M. Biocoal-Quality control and assurance. Biomass Bioenergy 2020,135, 105509. [CrossRef] 48. Wawrzkiewicz, M.; Podko´scielna, B. Innovative Polymer Microspheres with Chloride Groups Synthesis, Characterization and Application for Dye Removal. Processes 2022,10, 1568. [CrossRef] 49. Bazrafshan, E.; Amirian, P.; Mahvi, A.; Ansari-Moghaddam, A. Application of adsorption process for phenolic compounds removal from aqueous environments: A systematic review. Glob. NEST J. 2016,18, 146–163. 50. Han, R.; Li, H.; Li, Y.; Zhang, J.; Xiao, H.; Shi, J. Biosorption of copper and lead ions by waste beer yeast. J. Hazard. Mater. 2006 , 137, 1569–1576. [CrossRef] 51. Dada, A.; Olalekan, A.; Olatunya, A.; Dada, O. Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherms studies of equilibrium sorption of Zn2+ unto phosphoric acid modified rice husk. IOSR J. Appl. Chem. 2012,3, 38–45. 52. Ahmaruzzaman, M. Adsorption of phenolic compounds on low-cost adsorbents: A review. Adv. Colloid Interface Sci. 2008 ,143, 48–67. [CrossRef] 53. Özkaya, B. Adsorption and desorption of phenol on activated carbon and a comparison of isotherm models. J. Hazard. Mater. 2006,129, 158–163. [CrossRef] 54. Aksu, Z.; Gönen, F. Biosorption of phenol by immobilized activated sludge in a continuous packed bed: Prediction of breakthrough curves. Process Biochem. 2004,39, 599–613. [CrossRef] 55. Jain, A.K.; Gupta, V.K.; Jain, S.; Suhas. Removal of Chlorophenols Using Industrial Wastes. Environ. Sci. Technol. 2004 ,38, 1195–1200. [CrossRef] [PubMed] 56. Ariyanto, T.; Sarwendah, R.A.G.; Amimmal, Y.M.N.; Laksmana, W.T.; Prasetyo, I. Modifying Nanoporous Carbon through Hydrogen Peroxide Oxidation for Removal of Metronidazole Antibiotics from Simulated Wastewater. Processes 2019 ,7, 835. [CrossRef] 57. Vijayaraghavan, K.; Yun, Y.-S. Bacterial biosorbents and biosorption. Biotechnol. Adv. 2008,26, 266–291. [CrossRef] 58. Adegoke, K.A.; Bello, O.S. Dye sequestration using agricultural wastes as adsorbents. Water Resour. Ind. 2015 ,12, 8–24. [CrossRef] 59. Ptaszkowska-Koniarz, M.; Goscianska, J.; Bazan-Wozniak, A.; Pietrzak, R. Amine-Modified Carbon Xerogels as Effective Carbon-Based Adsorbents of Anionic Dye from Aqueous Solutions. Materials 2022,15, 5736. [CrossRef] [PubMed] 60. Hasan, H.M.I.; Alfutisi, H.M.M. Removing of Thymol Blue from aqueous solutions by Pomegranate peel. EPH-Int. J. Appl. Sci. 2020,6, 1–5. [CrossRef] Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). 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