Co esponding au ho : AMADOU KIARI Mahamane Nassi ou
Copy igh © 2025 Au ho (s) e ain he copy igh o his a icle. This a icle is published unde he e ms o he C ea i e Commons A ibu ion Liscense 4.0.
Compa a i e s udy o he adso p ion p ope ies o se e al mic opollu an s on
na u al phospha e om Tahoua/Nige and ac i a ed ca bon based on Hyphaene
hebaica shells
AMADOU KIARI Mahamane Nassi ou 1, *, SANDA MAMANE Ousmaila 2, I. HIMA Halidou 1, ZANGUINA
Adamou 1, MALAM ALMA Maman Mousbahou 1 and NATATOU Ib ahim 1
1 Labo a o y o Ma e ials, Wa e and En i onmen , Science and Technology Facul y, Abdou Moumouni Uni e si y, BP:
10662 Niamey, Nige .
2 Na ional School o Enginee ing and Ene gy Sciences, Uni e si y o Agadez, B.P: 199 Agadez, Nige .
Wo ld Jou nal o Ad anced Resea ch and Re iews, 2025, 27(02), 1972-1983
Publica ion his o y: Recei ed on 28 May 2025; e ised on 20 July 2025; accep ed on 27 July 2025
A icle DOI: h ps://doi.o g/10.30574/wja .2025.27.2.3024
Abs ac
This s udy compa es he adso p ion p ope ies o dyes on na u al phospha e om Tahoua and ac i a ed ca bon. The
phospha e used is na u al phospha e powde om Tahoua calcined a 850°C o wo hou s o inc ease he
o hophospha e (P2O5) con en . The ac i a ed ca bons used we e ob ained om he shell o he Hyphaene hebaica
(HT) nu by chemical ac i a ion wi h o hophospho ic acid (H3PO4) a 10% and 40% a a py olysis empe a u e o
450°C wi h an iso he mal pla eau o 1 hou 30 minu es. The shell was i s cha ac e ized. The mois u e con en
ob ained was 5.002 %, he ash con en was 5.828 % and he ola ile ma e con en (loss on igni ion) was 98.9587 %.
The ac i a ed ca bons p oduced (ACEs) ha e mass yields o a ound 42.85 % and 47.05 % when imp egna ed a 10%
and 40%, espec i ely. Nex , es s we e conduc ed o de e mine he adso p ion capaci ies o diiodine (I2), me hylene
blue (MB), and me hyl o ange (MO) on he ac i a ed ca bons p oduced (ACPs) and on na u al phospha e om Tahoua
(NPT). The esul s ob ained show ha he adso p ion equilib ium ime o me hyl o ange is 40 minu es and a ound
25 minu es o he de eloped ac i a ed ca bon (CAE) and Tahoua na u al phospha e (PNT), espec i ely. Finally, he
su ace unc ions and pH a ze o cha ge poin we e de e mined using he Boehm me hod and he i s bisec o
me hod, espec i ely. The su ace unc ions o CAEs a e acidic in na u e and he pH a ze o cha ge poin is below
neu ali y. Fo Tahoua na u al phospha e (PNT), he pH a ze o cha ge poin is sligh ly abo e neu ali y.
Keywo ds: Adso p ion; Ac i a ed Ca bon; Iodine Index; Me hylene Blue Index; Me hyl O ange; Na u al Phospha e
om Tahoua
1. In oduc ion
In ecen yea s, awa eness o he dange posed by pollu ion o a ious en i onmen al componen s (wa e , ai , soil, e c.)
has become a eali y ha conce ns all social and indus ial ac o s.
In Nige , he dyeing echniques used in he ex ile indus y ha e con ibu ed signi ican ly o wa e pollu ion. This
pollu ion is due o he discha ge o o ganic and ino ganic con aminan s ha a e ha m ul o human heal h and
ecosys ems. To his end, e luen discha ges om he ex ile indus y a e known o hei in ense colo a ion due o he
p esence o dyes, which a e ne e 100 % exhaus ed om he dye ba hs; a quan i y always emains in he e luen . The
discha ge o hese e luen s poses a majo dange o humans and he en i onmen . I is he e o e essen ial o limi his
pollu ion by implemen ing a dye emo al echnique adap ed o ou coun y (Nige ). The e a e a ious me hods o
emo ing chemicals (hea y me als, dyes, phenols, e c.) om e luen s. Among hese me hods, adso p ion on po ous
Wo ld Jou nal o Ad anced Resea ch and Re iews, 2025, 27(02), 1972-1983
1973
ma e ials is one o he mos widely used echniques [1–9]. I is a solid- luid ex ac ion p ocess ha equi es an adso ben
(solid) and an adso ba e (liquid o gas). Mic opo ous adso ben s a e widely used in he ex ac ion o chemical species
in aqueous o gaseous phases due o hei excellen adso p ion capaci y. This capaci y is linked o he la ge speci ic
su ace a ea and po osi y o he adso ben s [10,11]. Na u al phospha es and ac i a ed ca bons ha e been he subjec o
much esea ch in he sea ch o adso ben ma e ials. They a e o in e es in he ea men o indus ial was ewa e [1].
Phospha es ha e a wide ange o physical, chemical, and ex u al p ope ies. They a e capable o o ming bonds wi h
o ganic molecules o a ious sizes. Recen s udies ha e shown ha hese ma e ials, whe he na u al o syn he ic, can
emo e o ganic compounds om was ewa e [1]. Ac i a ed ca bon consis s mainly o ca bonaceous ma e ial wi h a
po ous s uc u e. I can be p oduced om any ca bon- ich aw ma e ial [12]. Nowadays, a ious s udies ha e ocused
on he p oduc ion and cha ac e iza ion o ac i a ed ca bons om se e al ypes o plan -based ma e ials such as: he
shell o Balani es aegyp iaca, he shell o Zizyphus mau i iana, he shell o Hyphaene hebaica [13], he b anches o
pe ioles o he ônie palm [8,9], bamboo s ems o canes [14], coconu [15], eucalyp us wood [16], he shells o
Tieghmelia, known as mako é, and Delonix, known as lamboyan [17], he shells o Pa ina i mac ophylla [18], and co ee
esidues [19].
I is in his con ex ha ou wo k i s in, he o e all objec i e o which is o conduc a compa a i e s udy o he dye
adso p ion p ope ies o na u al phospha e om Tahoua and ac i a ed ca bons. The la e a e p oduced om he shell
o he Hyphaene hebaica ke nel by chemical ac i a ion wi h o hophospho ic acid.
2. Ma e ials and me hods
2.1. Phospha e
Figu e 1 shows he aw na u al phospha e powde om Tahoua, and Figu e 2 shows he p ocessed na u al phospha e
powde om Tahoua.
Figu e 1 Raw na u al phospha e powde om Tahoua
Figu e 2 P ocessed na u al phospha e powde
om Tahoua
2.2. Shells o biomass used
The shells o Hyphaene hebaica (Figu e 3a) we e used o p epa e ac i a ed ca bon. These we e collec ed om he
was e dump o a local ma ke called Ka ako (Niamey, Nige ). They we e c ushed, washed wi h ap wa e o emo e dus ,
insed wi h dis illed wa e , and hen d ied in an o en a 105 °C o 24 hou s (Figu e 3b).
Wo ld Jou nal o Ad anced Resea ch and Re iews, 2025, 27(02), 1972-1983
1974
(a) (b)
Figu e 3 Hyphaene hebaica shells (a) and c ushed shells (b)
2.3. Reagen s used
The eagen s used in his wo k a e p esen ed in Table 1.
Table 1 Chemicals use
Chemicals
Molli mass (g/mol)
Pu (%)
Sou ces
O hophospho ique Acid (H3PO4)
98
85 %
Me ck
Me hylene bleu (C16H18Cl3S)
319.86
-
Sigma-Ald ich
Sodium hiosul a e (Na2S2O3.5H2O)
Iodine
248.18
126.9
99 %
-
Sigma-Ald ich
Sigma-Ald ich
3. Me hodology
3.1. Phospha e p ocessing
Calcina ion is used o en ich he o hophospha e (P2O5) con en and educe he o ganic ca bon and ca bon dioxide
con en in phospha es. The p inciple o his p ocess is o hea he na u al phospha e powde om Tahoua o a high
empe a u e o 850 °C o 2 hou s [20].
3.2. Cha ac e iza ion o biomass
3.2.1. Mois u e con en and ola ile ma e con en
Mois u e con en and ola ile ma e con en we e de e mined in acco dance wi h AFNOR XP CEN/TS 14774 and
AFNOR XP CEN/TS 15148 s anda ds, espec i ely [6,21]. Fi s , po celain c ucibles o mass P con aining 2 g o biomass
we e d ied in an o en a 105 °C o 24 hou s. A e cooling in a desicca o , he c ucibles we e weighed again. To
de e mine he ola ile ma e con en , he d ied samples we e placed in a mu le u nace a 1000°C o 3 hou s. A e
cooling in a desicca o , he whole ba ch was weighed. The mois u e con en (H) and ola ile ma e con en (PF) a e
gi en by exp essions 1 and 2 espec i ely.
(H)= P1− P2
P1− P × 100 … .. (1)
(P. F )= P2− P3
P2− P ×100 … …. (2)
Whe e P1 and P2 a e he masses o he c ucible + sample be o e and a e d ying in he o en; P3 is he mass o he whole
a e ca boniza ion in he u nace.
Wo ld Jou nal o Ad anced Resea ch and Re iews, 2025, 27(02), 1972-1983
1975
3.2.2. Ash con en
The ash con en was de e mined in acco dance wi h s anda d AFNOR XP CEN/TS 14775 [6,21]. In a po celain c ucible
wi h an emp y mass m1, 1 g o biomass g ound o a pa icle size o less han 200 μm was in oduced. The sample was
mine alized a 815 °C using a mu le u nace o 2 hou s. A e cooling in a desicca o , he whole hing (sample +
c ucible) was weighed o ge he mass m3.
The ash con en is gi en by he ollowing equa ion:
(%C)= m3 − m1
m2− m1
× 100 … ….. (3)
Wi h m2, he mass o he c ucible + sample be o e mine aliza ion.
3.2.3. Appa en densi y
To de e mine he appa en densi y, a 50 cm3 es ube wi h an emp y mass m1 was illed wi h biomass g ound o a
pa icle size o less han 200 μm, and he mass m2 was eco ded [6,21].
The densi y is gi en by he equa ion
ρ = m2 − m1
V … … (4)
3.3. P oduc ion o ac i a ed ca bon
3.3.1. P epa a ion o ac i a ed ca bon
The me hod used o p epa e ac i a ed ca bon is chemical ac i a ion [22–25]. The p e ea ed biomass is imp egna ed
wi h wo solu ions o H3PO4 a 10 % and 40 %, a a a e o 20 g o biomass pe 100 ml o solu ion. Imp egna ion is ca ied
ou unde magne ic s i ing o 24 hou s a a mosphe ic p essu e and oom empe a u e. The samples we e hen
il e ed on ashless Büchne il e pape , washed wi h dis illed wa e , and d ied in an o en a 105 °C o 24 hou s. A e
emo al om he o en, he samples we e cooled in a desicca o o 15 minu es. Once d ied, each imp egna ed sample
was placed in a c ucible wi h a lid, and he assembly was placed in a mu le u nace a a empe a u e o 450 °C, wi h a
hea ing a e o 2.66 °C/min and an iso he mal pla eau o 90 min a he end o py olysis. A e he 90-minu e pla eau a
he inal py olysis empe a u e, he c ucible was emo ed om he o en and cooled in a desicca o o 15 minu es. A e
cooling, he cha coal was washed ho oughly wi h dis illed wa e o emo e impu i ies un il he pH was close o neu al,
hen d ied in an o en a 105°C. The ac i a ed ca bons hus ob ained we e g ound and hen sie ed o ob ain g ains o a
size less han o equal o 500 μm.
3.4. Cha ac e iza ion
3.4.1. Mass yield a e py olysis
This is an impo an quan i a i e cha ac e is ic o ac i a ed ca bon ha e lec s he loss o biomass mass du ing
py olysis.
The ollowing o mula gi es he exp ession o mass yield
Yield = m
mi
× 100 … … (5)
inal mass (m ) and ini ial mass (mi).
3.4.2. Su ace unc ion
The acid and base unc ions on he su ace o ac i a ed ca bons we e de e mined and quan i ied using he Boehm
i a ion me hod [26]. (Boehm, 1994). To de e mine hese unc ions, 0.2 g o AC we e b ough in o con ac wi h 20 mL
o each o he ollowing solu ions: NaOH, Na2CO3, NaHCO3, C2H5ONa, and HCl a 0.1 M. Each solu ion was s i ed o 24
hou s o ensu e ha a maximum amoun o he su ace g oups o AC eac ed, hen il e ed; a e il a ion, 10 mL o each
o he i e solu ions was measu ed. The basic solu ions a e i a ed wi h 0.1 M hyd ochlo ic acid using h ee d ops o
Wo ld Jou nal o Ad anced Resea ch and Re iews, 2025, 27(02), 1972-1983
1976
b omo hymol blue, phenolph halein, b omoc esol g een, and helian hin as colo indica o s, espec i ely, and he acid
solu ion is i a ed wi h 0.1 M sodium hyd oxide using b omo hymol blue as he colo indica o .
The quan i ica ion o acid and base g oups is pe o med using he ollowing o mula
néqR = NiVi− N V … .. (6)
no is he numbe o equi alen g ams ha eac ed; Ni i is he numbe o equi alen g ams be o e he eac ion; NV is
he numbe o equi alen g ams a e he eac ion.
3.4.3. pH a ze o cha ge poin (pHPZC)
The pH a ze o cha ge poin (pHPZC), which allows he ne cha ge o he ma e ial su ace o be de e mined, was calcula ed
using he me hod desc ibed by Ousmaila e al., [5]. This me hod in ol es p epa ing 0.1 M sodium chlo ide (NaCl)
solu ions a di e en pH alues, namely 2, 4, 6, 8, and 10. The pH alues we e adjus ed wi h a pH me e using sodium
hyd oxide and hyd ochlo ic acid solu ions. In a 50 mL beake , 0.1 g o CA was mixed wi h 20 mL o each solu ion. The
mix u e was s i ed magne ically o 72 hou s. The suspension was il e ed h ough il e pape and he pH o he il a e
was measu ed. Then, he pH = (pHi) cu e was plo ed. The in e sec ion poin be ween his cu e and he i s bisec o
gi es he pH a he ze o-loading poin o he ac i a ed ca bon in ques ion.
pH : inal pH and pHi: ini ial pH.
3.5. Adso p ion o mic opollu an s
3.5.1. Iodine index
The iodine index is an impo an cha ac e is ic in he e alua ion o he mic opo es o ac i a ed ca bon. In his s udy, i
was de e mined using he me hod applied by GUEYE [16]. Thus, a olume o 20 mL o a 0.02 N iodine solu ion was
b ough in o con ac wi h 0.2 g o ac i a ed ca bon o 4 min. The ea ed solu ion was il e ed, and hen 10 mL o il a e
was i a ed wi h a 0.1 N sodium hiosul a e solu ion in he p esence o a ew d ops o s a ch pas e. Finally, he iodine
index (Id) exp essed in mg/g was calcula ed using equa ion (7).
𝐼𝑑=
(C0− C hioV hio
2VI2 )MI2Vads
mca
… … (7)
Whe e, Id: adso p ion capaci y o I2; C0: ini ial concen a ion o he I2 solu ion (in mol/L); C hio: concen a ion o Na2S2O3
(in mol/L); V hio: olume o Naso₃ a equi alence (in mL); VI₂: olume o iodine i a ed (in mL); MI₂: mola mass o I₂
(in g/mol); Vads: adso p ion olume (in mL); mca: mass o adso ben used (in g).
adso p ion olume (in mL); mica: mass o adso ben used (in g).
3.5.2. Me hylene Blue (MB) Index
The MB index, exp essed in mg. g-1, ep esen s he adso p ion capaci y o medium-sized molecules o he pu pose o
e alua ing mesopo es and mac ospo es.
a) P epa a ion o s anda d MB es solu ion
Place 1.2 g o MB in a 1 L olume ic lask. Fill he lask wi h dis illed wa e o he ma k. The solu ion is le o s and o
app oxima ely one nigh . The solu ion is hen es ed by adding 0.25 % ace ic acid (i.e., 5.0 ml pe 1 L o solu ion). Fo
his pu pose, a es solu ion was p epa ed by dilu ion co esponding o an abso bance o 0.840 ± 0.01 a a wa eleng h
o 620 nm.
b) P ocedu e o de e mining he MB index
Me hylene blue adso p ion es s we e pe o med using he CEFFIC p o ocol [5,6]. In a 250 mL E lenmeye lask, we
added 100 mg o adso ben o 100 mL o s anda d MB solu ion. The mix u e was s i ed o 20 min. A e s i ing, he
mix u e was il e ed and he esidual concen a ion o me hylene blue was measu ed a 𝞴 = 620 nm using a UV- isible
spec opho ome e .
Wo ld Jou nal o Ad anced Resea ch and Re iews, 2025, 27(02), 1972-1983
1977
The me hylene blue index is gi en by:
IBM =(𝐶𝑖− 𝐶𝑟)𝑉𝑀
𝑚 × 100 … .. (8)
Wi h IBM: adso p ion capaci y o CA (in mg/g); Ci: ini ial concen a ion o BM solu ion (in mol/L); C : esidual
concen a ion o BM solu ion (in mol/L); V: olume o BM solu ion (in mL); M: mola mass o BM; m: mass o adso ben
used (in g)
3.6. Me hyl o ange (MO) adso p ion kine ics
In a 500 mL beake , 200 mL o me hyl o ange (MO) solu ion wi h an ini ial concen a ion o 50 mg/L and 80 mg o
adso ben a e added. This mix u e is s i ed a 25 °C. A egula in e als, 1 mL o he mix u e was sampled and il e ed
using a 0.45 μm po e size il e pape . A JENWAY 6305 UV- isible spec opho ome e was used o measu e he esidual
MO concen a ion a a wa eleng h o 520 nm. The quan i ies adso bed a equilib ium (Qe) we e calcula ed using
equa ion 9.
Qe=(Ci− C )
m × V … .. ( 9)
Whe e Ci and C a e he ini ial and esidual concen a ions o me hyl o ange (in mg. L-1); V is he olume (in L) o he
solu ion used o he adso p ion es s; and m is he mass (in g) o adso ben .
4. Resul s and discussion
4.1. Cha ac e iza ion o biomass
The composi ion and physical p ope ies o biomass a e pa ame e s ha in luence i s con e sion in o ac i a ed ca bon
[13]. Table 2 summa izes he esul s o he immedia e analysis pe o med on he shell o Hyphaene hebaica (HT).
Table 2 Immedia e analysis esul s
Biomass
Mois u e con en (%)
Ash con en
(%)
Ca bon con en (%)
Ac ual densi y g/cm3
Hyphaene hebaic (HT)
5.0026
5.8286
74.850
0.3220
Table 2 shows ha he ash con en o biomasses is less han 6 %. This indica es ha hese biomasses can be used o
p oduce ac i a ed ca bons wi h la ge speci ic su ace a eas [8] .This pa ame e has a signi ican e ec on he quali y o
ac i a ed ca bon. I is also known ha high ash con en educes he speci ic su ace a ea o ac i a ed ca bons [13,16].
In ac , ash in e cala es in o he ca bon s uc u e, clogs he po es, and educes he po osi y o he ac i a ed ca bon.
Unlike he mois u e and ash con en , which a e ela i ely low, he ca bon con en is e y high, a a ound 74.85 %.
Biomass is he e o e mainly composed o o ganic ma e . Such ola ile ma e alues a e a good indica o o ob aining
ac i a ed ca bon wi h a high deg ee o g aphi iza ion, a high g oss calo i ic alue (GCV), and su icien unc ional g oups
[13,16].
Wo ld Jou nal o Ad anced Resea ch and Re iews, 2025, 27(02), 1972-1983
1978
4.1.1. Mass yield
The mass yield esul s a e py olysis a e shown in Table 3.
Table 3 Mass yield esul s a e py olysis o CAs
Biomass
H3PO4
concen a ion
(%)
Imp egna ion
ime
(h)
Py olysis
empe a u e
(℃)
Hea ing
a e °C/min
Ca boniza ion
ime
(h)
Mass
yield
(%)
Hyphaene
hebaica
10
24
450
2.66
1 h 30
42.85
40
24
450
2.66
1 h 30
47.05
These esul s show ha inc easing he concen a ion o he ac i a ing agen H3PO4 inc eases he mass yields a e
py olysis o CAs. This can be explained by he ac ha H3PO4, as an ac i a ing agen , is a dehyd a ing agen ha delays
he mal decomposi ion, limi s he loss o ola ile ma e , and leads o he o ma ion o a igid ca bon ma ix [5,21].
4.1.2. Su ace unc ions
Table 4 shows he mEq/g con en o he adso ben s' unc ions.
Table 4 Su ace unc ion o adso ben s
Adso ben
ca boxylic
lac one
phenol
ca bonyl
To al acid
Basic o al
CA-HT 10 %
1.2
1.3
3.2
2.4
8.1
-
CA-HT 40 %
1.5
2.1
2
2.1
7.7
-
As expec ed, wi h his acid chemical ac i a ion, he CA-HT 10% and CA-HT 40% ac i a ed ca bons p oduced con ain a
la ge amoun o acid g oups and no basic g oups. This can be explained by he ac ha he ACEs we e no exposed o
oxygen below 200°C o abo e 700°C, hey did no unde go hyd ogen ea men , and hey we e no degassed a oom
empe a u e, as his is he s age a which basic unc ions a e in oduced. Simila esul s ha e been epo ed in he
li e a u e [5,21]. These acidic su ace g oups a e p obably due o polyphospha es bound o he su ace o he ca bon
and o ca boxylic g oups. O hophospho ic acid ac s as a ca alys by p omo ing bond clea age eac ions and acili a ing
c oss-linking ia cycliza ion, condensa ion, and he o ma ion o phospha e and polyphospha e bonds [27]. Ca bonyl
and phenolic g oups p edomina e on hei su ace.
4.1.3. pH a ze o cha ge poin (pHPCN)
Figu es 4, 5, and 6 show he pH de e mina ion cu es a ze o cha ge poin o ac i a ed ca bons ac i a ed wi h
o hophospho ic acid and na u al phospha e om Tahoua, espec i ely.
Wo ld Jou nal o Ad anced Resea ch and Re iews, 2025, 27(02), 1972-1983
1979
Figu e 4 De e mina ion o he pHPCN o CA HT 10% ac i a ed wi h H3PO4
Figu e 5 De e mina ion o he pHPCN o CA HT 40 % ac i a ed wi h H3PO4
Figu e 6 De e mina ion o he pHPCN o PNT
The pH alues a he ze o cha ge poin o ac i a ed ca bons a e all below neu ali y (pH < 7). They ange om 2.54 o
4.55. Simila esul s ha e been obse ed in o he s udies [27,28]. A a pH highe han hese alues, he su ace o he
ac i a ed ca bon is nega i ely cha ged, whe eas i is posi i ely cha ged a a pH lowe han he pHpcn. As o PNT, he
7.32
Wo ld Jou nal o Ad anced Resea ch and Re iews, 2025, 27(02), 1972-1983
1980
pH alue a he ze o-cha ge poin is close o neu ali y a 7.32. A a pH highe han his alue, he su ace o PNT is
nega i ely cha ged, whe eas i is posi i ely cha ged a a pH lowe han he pHpcn.
4.2. Adso p ion o mic opollu an s
4.2.1. Iodine index
The iodine index esul s o he ac i a ed ca bons p oduced and he na u al phospha e om Tahoua a e shown in Table
5.
Table 5 Iodine index esul s in mg/g
PNT
CA HT 10 %
CA HT 40 %
V hio (mL)
3
0.7
0.1
QI2
126.90
418.77
494.91
In he case o CAs, he esul s show ha he pa ame e in luencing he iodine index is he concen a ion o he ac i a ing
agen (H3PO4). Se e al au ho s ha e shown ha he iodine index inc eases wi h he concen a ion o he ac i a ing agen
[4,21,29]. These esul s a e simila o hose ob ained by [4,21].
Fo phospha e, he adso p ion capaci y o I2 is lowe han ha o he wo (2) ACs. This could be due o he ac ha aw
na u al phospha e om Tahoua has been ound o be a ma e ial wi h mode a e adso p ion a ini y compa ed o
ac i a ed ca bons o iodine emo al.
4.2.2. De e mina ion o he Me hylene Blue (MB) index
The MB esul s o he ac i a ed ca bons p oduced and he na u al phospha e om Tahoua a e shown in Table 6
Table 6 Me hylene blue index esul s in mg/g
Adso ben
PNT
CA HT 10%
CA HT 40%
BM index
548.879
810.01
886.72
I can be seen ha he adso p ion capaci y o BM by CA inc eases wi h he concen a ion o he ac i a ing agen (H3PO4).
These esul s a e simila o hose ob ained by [4,21].
Fo PNT, he adso p ion capaci y alue ob ained o BM is ela i ely low compa ed o hose ob ained by ACs. This could
be due o he ac ha aw Tahoua na u al phospha e has been ound o be a ma e ial wi h mode a e adso p ion a ini y
compa ed o ac i a ed ca bons o BM emo al.
4.2.3. Me hyl o ange con ac ime
The kine ic s udy allows us o de e mine he con ac ime equi ed o each adso p ion equilib ium. To do his, we
moni o ed he adso p ion kine ics o MO o an ini ial concen a ion o 50 mg/L, wi h a mass o 80 mg o adso ben .
The esul s o he adso p ion kine ics o MO on he adso ben s a e p esen ed in Figu es 7
