Copy igh © ISRG Publishe s. All igh s Rese ed.
DOI: 10.5281/zenodo.17339353
24
ISRG PUBLISHERS
Abb e ia ed Key Ti le: ISRG J Eng Technol
ISSN: 3107-5894 (Online)
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Volume – I Issue-III (Sep embe -Oc obe ) 2025
F equency: Bimon hly
Compa a i e S udy on Phospho us Remo al E iciency o Phospho us Locking Agen
and I on-Aluminium Ma e ials
Bowei Zhang
Nanjing Fo eign Language School 60 Huixiu Road, Nanjing, Jiangsu, China
| Recei ed: 10-10-2025 | Accep ed: 12-10-2025 | Published: 13-10-2025
*Co esponding au ho : Bowei Zhang
Nanjing Fo eign Language School 60 Huixiu Road, Nanjing, Jiangsu, China
Abs ac
Excessi e phospho us o e loading in lakes, which leads o eu ophica ion, is de imen al o he aqua ic ecosys em and wa e
quali y. The use o adso p ion o emo e phospho us is now an a ac i e me hod o ea men due o i s easy ope a ion and low
cos . The s udy compa ed he adso p ion o phospho us using wo ac o s: a comme cial phospho us locking agen and i on-
aluminium esidual ma e ials (FARS) gene a ed du ing wa e ea men p ocedu es. The pseudo-phospha e was ewa e was
s udied in e ms o adso p ion kine ics and iso he ms using ba ch expe imen s. I was gene a ed by he esul s ha FARs
expe ienced much highe phospho us adso p ion concen a ions pe kine ic unc ion (qm = 18.35 mg/g) han he phospho us
locking agen (qm = 3.69 mg/g), and in bo h ins ances, p o ided iable i s o pseudo-second-o de kine ic models (R² mo e han
0.98). The b ain o he phospho us locking agen unde es by Iso he m yielded esul s in he cases o bo h he Langmui model
(qm = 25.06 mg/g s 16.87 mg/g e sus FARs) and in he F- ype and L- ype bes p ac ices, bo h o which ga e a posi i e esul ,
al hough some cases yielded no esul . The inc eased kine ic ac i i y o FARs can be explained by he high and p oduc i e
p oduc ion o su ace hyd oxyl g oups on i on and aluminium oxides, which o e an oppo uni y o he chemical complexa ion o
phospha e ions by o ming Fe-O-P and Al-O-P bonds. When used o ea phospho us in pollu ed wa e sou ces, such esul s
sugges ha FARs ep esen a cos -e icien and en i onmen ally iendly al e na i e, as hey a e o e ed o gua an ee he
s abiliza ion o he was e while simul aneously imp o ing wa e quali y.
Keywo ds:
phospho us emo al, adso p ion kine ics, i on-aluminium ma e ials, phospho us locking agen , wa e ea men
esiduals, eu ophica ion con ol
Copy igh © ISRG Publishe s. All igh s Rese ed.
DOI: 10.5281/zenodo.17339353
25
1. In oduc ion
Lakes play a c ucial ole in balancing he wa e shed, sus aining
biodi e si y, and p o iding wa e o homes and indus ies.
Subsequen ly, phospho us pollu ion has accele a ed wi h apid
socioeconomic de elopmen , esul ing in he discha ge o poo ly
ea ed was es ha cause eu ophica ion and algal blooms (Khalili
& Mo idi, 2025). As phospho us is he p ima y nu ien causing
eu ophica ion, i is c ucial o educe i s le els in wa e basins o
imp o e he quali y o he en i onmen . The con en ional
echniques o phospho us emo al, including biological p ocesses,
mic obial p ocesses, and adso p ion, exhibi a ying deg ees o
e icacy. Al hough biological o mic obial me hods ha e p o en
e ec i e in phospho us emo al, hey also lead o high sludge
p oduc ion and clogging issues (Zahed e al., 2022). Adso p ion, on
he o he hand, o e s ad an ages such as low cos s, high
e iciency, and ease o ope a ion. Al hough hey possess hese
ad an ages, ypical adso ben s, such as biocha , dia omaceous
ea h, mesopo ous silica, and me al-o ganic amewo ks, acco ding
o Biswal and Balasub amanian (2023), ha e limi a ions, including
apid sa u a ion and slow egene a ion, which limi hei la ge-
scale use.
Indus ial byp oduc s, such as a apulgi e and wa e wo ks sludge,
which ha e been poo ly ea ed in China (in China, 80% o sludge
has been dumped imp ope ly, acco ding o Zhang e al. (2017)),
pose se ious en i onmen al p oblems due o inadequa e disposal
p ac ices, including land illing and dumping. Thei su aces,
howe e , con ain a la ge quan i y o ac i e me al oxides, making
hem e y ac i e in adso bing ino ganic phospho us (Zhang e al.,
2017). The use o hese p oduc s as phospho us-binding
subs ances, as well as i on-aluminium composi es, is bene icial in
wo ways: i mi iga es he consequences o phospho us pollu ion in
wa e , and i enhances he alo iza ion o was e.
This s udy aims o compa e he adso p ion o phospho us by
a ious ma e ials h ough simula ed was ewa e unde a ying
condi ions. Pa icula ly, i seeks o (1) de e mine he quali y o
wa e in nea by lakes and i e s, and (2) examine adso p ion
iso he ms and kine ics o phospho us in each ma e ial. The s udy's
esul s will shed u he ligh on he mechanism o phospho us
emo al, acili a e he de elopmen o new, po en wa e ea men
me hods, and con ibu e o he managemen and con ol o
phospho us-laden wa e sys ems.
2. Ma e ials and Me hods
2.1 Expe imen al Ma e ials
In his esea ch, wo ypes o adso ben s we e used: he phospho us
locking agen and i on-aluminium ma e ials (FARs). The
phospho us locking agen is one o he comme cial p ocesses
de eloped o ap phospho us in wa e . The de elopmen o
ma e ials based on me hodologies used in ea lie esea ch on wa e
usage esiduals, wi h i on-aluminium (FARs) as he basic ma e ial,
was achie ed h ough composi e s uc u es o i on and aluminium
de i ed om wa e ea men sludge. These subs ances we e
imp egna ed wi h bo h i on and aluminium hyd oxides, which also
p o ed o be ac i e loca ions o he a achmen o phospho us.
Simula ed phospha e was ewa e was cons uc ed by adding
analy ical-g ade po assium dihyd ogen phospha e (KH₂PO₄) and
aking measu emen s by changing he phospho us concen a ion in
he o iginal solu ion o he ex en desi ed o adso p ion.
2.2 Expe imen al Ins umen s and Reagen s
Wi h ins umen s such as a cons an empe a u e shake o main ain
eac ion condi ions, an ul a iole - isible spec opho ome e o
de e mine phospho us concen a ion, a pH me e o measu e
solu ion pH, a 0.45 μm il e memb ane o sepa a e solids and
liquids, and an analy ical balance o weigh ma e ials accu a ely.
The eagen s used included he eassu ed phospho us sou ce
(po assium dihyd ogen phospha e, KH2PO4), pH modi ie s such as
sul u ic acid and sodium hyd oxide, and a neu al eagen
(deionized wa e ) o p epa e he solu ion.
2.3 Expe imen al Me hods
2.3.1Phospho us S anda d Cu e P epa a ion
A phospha e s ock solu ion was p epa ed by d ying gua an eed
eagen -g ade po assium dihyd ogen phospha e (KH₂PO₄) a 110°C
o 2 hou s, cooling i in a desicca o , and dissol ing 0.2197 g in
wa e . The solu ion was ans e ed o a 1000 mL olume ic lask,
and 5 mL o 1:1 sul u ic acid was added. The solu ion was hen
u he dilu ed wi h wa e o he ma k, esul ing in a concen a ion
o 50.0 μg phospho us pe millili e. The p epa a ion o he
phospha e s anda d solu ion in ol ed ans e ing 10mL o s ock
solu ion in o a 250mL olume ic lask and dilu ing i wi h wa e o
achie e a phospho us concen a ion o 2.00 μg phospho us pe
millili e . This wo king solu ion was eshly p epa ed be o e use.
S anda d cu e cons uc ion in ol ed adding 0, 0.50, 1.00, 3.00,
5.00, 10.0, and 15.0 mL o phospha e s anda d wo king solu ion o
indi idual 50 mL s oppe ed colou ime ic ubes, whe e each was
dilu ed o 50 mL. The phospho us esul s in he inal ubes we e
used as he Y-axis alues, and he measu ed abso bance alues
we e used as he X-axis. All hese da a, when pai ed acco ding o
he s anda ds o linea eg ession, yielded a calib a ion equa ion o
be used o u he de e mina ion o he phospho us le el.
2.3.2Adso p ion Kine ics Expe imen s
The p epa a ion o he phospha e s ock solu ion was ca ied ou
using he same p ocess as he Phospho us S anda d Cu e
P epa a ion, yielding a phospha e s ock solu ion o 50.0 μg o
phospho us pe millili e. The expe imen al p ocedu e consis ed o
h ee s eps. Fi s , 0, 0.50, 1.00, 3.00, 5.00, 10.0, and 15.0 mL o
phospha e s ock solu ion we e added o sepa a e con aine s and
dilu ed o 50 mL. Second, 0.1 g o adso ben ma e ial was
in oduced in o each o he solu ions. Thi d, samples we e il e ed,
and he phospho us esidual in he supe na an was
spec opho ome ically de e mined a e a 24-hou shaking
du a ion a a cons an empe a u e shake . The kine ic expe imen s
in ol ed moni o ing phospho us emo al o e ime pe iods o 0,
0.5, 1, 2, 3, 4, and 6 hou s, which allowed o he desc ip ion o
bo h he dynamics o he adso p ion a e and he equilib ium.
2.3.3Adso p ion Iso he m Expe imen s
P epa a ion o he phospha e s ock solu ion ollowed he s anda d
p ocedu e again. The s eps used in he expe imen in ol ed:
Fi s ly, 15.0 mL o phospha e s ock solu ion was measu ed and
in oduced in o he con aine s, and hen dilu ed o 500 mL, he eby
es ablishing he ini ial phospho us concen a ion. Second, 1 g o
adso ben ma e ial was in oduced o his solu ion, keeping he
solid- o-liquid a io cons an . Thi d, samples we e aken a 0, 0.5,
1, 2, 3, 4, and 6 hou s, il e ed h ough 0.45 μm memb anes, and
he emaining phospho us concen a ions in he supe na an o he
samples we e eco ded. By using his p ocedu e, i was possible o
cons uc adso p ion iso he ms ha showed a ela ionship a
equilib ium be ween he s a is ical phospho us concen a ion in he
solu ion and he phospho us a ailable as an adso ben .
Copy igh © ISRG Publishe s. All igh s Rese ed.
DOI: 10.5281/zenodo.17339353
26
2.4 Da a Analysis Me hods
Mass balance equa ion was used in compu ing he adso p ion
capaci y; ha is, qe = (C₀ - Ce) × V / m; qe is he adso p ion
capaci y in equilib ium (mg/g), C0 is he ini ial phospho us
(mg/L), Ce is he equilib ium phospho us (mg/L), V is he olume
o solu ion (L) k so m is he weigh o adso ben (g). A non-linea
eg ession analysis was used o i he model pa ame e s, which
consis ed o he co ela ion coe icien (R²), he adso p ion a e
cons an (k), and he highes adso p ion capaci y (qm). The kine ic
da a ha e been i ed wi h he pseudo- i s -o de and pseudo-
second-o de kine ic models. Al e na i ely, he iso he m da a we e
i ed using he Langmui and he F eundlich iso he m
o mula ions. They would be u ilized o cha ac e ize he adso p ion
p ocesses and he pe o mance o he ma e ial. Table 1 summa ises
he inal esul s.
Table 1: Summa y o Expe imen al Condi ions and Pa ame e s
Expe imen
Type
Ini ial P
Concen a ion
Adso ben
Dose
Solu ion
Volume
Con ac
Time
Tempe a u e
pH
Agi a ion
Speed
S anda d Cu e
0-0.6 mg/L
-
50 mL
-
25°C
~7
-
Kine ics
1.5 mg/L
0.1 g
50 mL
0-24 h
25°C
~7
150 pm
Iso he ms
1.5 mg/L
1.0 g
500 mL
0-6 h
25°C
~7
150 pm
3. Resul s and Analysis
3.1 Adso p ion Kine ics Cha ac e is ics
The explici kine ic na u e o phospho us adso p ion by he wo
cha ac e s esul ed in a empo al e olu iona y p ocess,
cha ac e ized by a g adual app oach o equilib ium. The
phospho us locking agen and i on-aluminium ma e ials showed
high phospho us emo al in he i s hou , indica ing a s ong
a ini y be ween he adso ben su aces and phospha e ions.
None heless, he e we e la ge di e ences in he adso p ion a e and
end capaci y. The i on-aluminium adso p ion kine ics we e much
g ea e and app oached equilib ium wi hin a du a ion o 2-3 hou s,
whils he phospho us locking agen did no achie e equilib ium
p og essi ely as was expec ed.
Model i ing h ough quan i a i e kine ic analysis p o ided
addi ional in o ma ion on he adso p ion mechanisms. Using
pseudo- i s -o de and pseudo-second-o de kine ics models o
analyze he expe imen al da a, i was ound ha bo h ma e ials i
he pseudo-second-o de kine ics model mo e e ec i ely. Fo i on-
aluminium ma e ials, he pseudo-second-o de model yielded a
maximum adso p ion capaci y (qm) o 18.35 mg/g, wi h a a e
cons an (k₂) o 0.24 g/(mg·min) and a co ela ion coe icien (R²)
o 0.99. Pseudo- i s -o de i ing, in con as , yielded a qm o
17.58 mg/g wi h k₁ o 2.96 min⁻¹ and R² o 0.96 as obse ed in
Table 2. I is in e es ing o no e he g ea e R² o he pseudo-
second-o de model, which sugges s ha chemical adso p ion
p e ails in he phospho us abso p ion p ocess by i on-aluminum
ma e ials.
In he case o he phospho us locking agen , pseudo-second-o de
kine ics once again o e ed an excellen i wi h qm = 3.69 mg/g, k2
= 0.47 g(mg·min), and R2 = 0.98, as opposed o pseudo- i s -o de
kine ic pa ame e s o qm = 4.35 mg/g, k1 = 0.98 min-1, and R2 =
0.92 (Table 2). The alues achie ed o he co ela ion coe icien s
o pseudo-second-o de models indica e ha he s a egy o
elec ons (chemiso p ion) ep esen s he a e-limi ing s ep in he
adso p ion o phospho us wi h bo h adso ben s, a ibu ing o he
chemiso p ion me hodology. This is in line wi h al eady known
ac s ha me al oxide su aces eac wi h phospha e by being
in ol ed in inne -sphe e in e ac ions, o ming complexes ia
ligand exchange eac ions.
Table 2: Kine ic Model Pa ame e s o Phospho us Adso p ion
Ma e ial
Pseudo-Fi s -O de Model
Pseudo-Second-O de Model
qm (mg/g)
k₁ (1/min)
R²
qm (mg/g)
k₂ (g/mg·min)
R²
Phospho us Locking Agen
4.35
0.98
0.92
3.69
0.47
0.98
I on-Aluminum Ma e ials
17.58
2.96
0.96
18.35
0.24
0.99
The as di e ence in adso p ion capaci y be ween i on-aluminium
(18.35mg/g) and phospho us locking agen (3.69mg/g) in kine ic
expe imen condi ions is a no able aspec wi h p ac ical
implica ions. Such a signi ican 5- old di e ence in adso p ion a e
indica es ha he mo e p omising i on-aluminium ma e ials ha e
mo e ac i e si es on which phospho us may be bound, and hey a e
a ailable. I is also possible o gain ce ain insigh s in o he
mechanism wi h he help o a e cons an a ia ion. P esumably,
he me e ac ha k2 o i on-aluminium subs ances is less (0.24
e sus 0.47 g/(mg·min)) could indica e a sluggish adso p ion
p ocess, e en hough he capaci y is la ge , which is possibly he
esul o di usion cons ain s wi h he pene a ion o he phospha e
ions o he po ous su aces o he i on-aluminium ma ix. The
phospho us locking agen , on he o he hand, has a g ea e a e
cons an , which means ha i adso bs as e ini ially; howe e , i s
inal capaci y is low.
3.2 Adso p ion Iso he m Cha ac e is ics
Adso p ion iso he m expe imen s e ealed he equilib ium
co ela ions be ween phospho us concen a ion in a solu ion and
he quan i y o adso bed phospho us, p o iding undamen al
he modynamic in o ma ion abou he connec ion be ween he ype
o adso ben s and he adso ba es. Successi e cu es o bo h
ma e ials exhibi ed s e eo ypical o ms o L- ype (Langmui ype)
and F- ype (F eundlich ype) adso p i e beha iou , wi h a ac i e
adso p ion ini ially s eep a low phospho us concen a ions and
g adually ising owa ds a pla eau a high phospho us
concen a ions.
The Langmui iso he m model assumes monolaye adso p ion on
homogeneous su ace si es, which ha e a ini e capaci y and do no
exhibi in e ac ion be ween adso bed molecules. A maximum
adso p ion capaci y o 25.06mg/g and a Langmui cons an o 0.09
L/mg, along wi h an excellen co ela ion coe icien R² o 0.98,
Copy igh © ISRG Publishe s. All igh s Rese ed.
DOI: 10.5281/zenodo.17339353
27
we e ob ained by applying his model o he expe imen al da a used
o calcula e he adso p ion capaci y o he phospho us locking
agen . The Langmui i ing was used o de e mine he qm o i on-
aluminum ma e ials, which was 16.87mg/g, kL o 0.06 L/mg, and
R² = 0.96. The alues o R² g ea e han 0.96 o bo h ma e ials
demons a e ha he equilib ium adso p ion beha iou can be well
explained using he Langmui model, indica ing ha he adso p ion
o phospho us is p ima ily go e ned by he o ma ion o a
monolaye on he adso ben su aces.
The Langmui cons an , kL, ela es o he adso p ion ene gy and
a ini y be ween he adso ben and he adso ba e. Gi en ha , an
inc ease in kL alue implies inc eased binding a ini y. The ac
ha he kL o phospho us locking agen is ba ely abo e ha o he
phospha e binding ca ie (0.09 e sus 0.06 L/mg) indica es
sligh ly s onge phospha e binding, bu he a ia ion is no e y
signi ican . Mo e impo an ly, he alues o Langmui qm a e
heo e ical maximum adso p ion capaci ies based on he heo y o
ull su ace sa u a ion. The ac ha he qm o phospho us locking
agen (25.06mg/g) was highe han he qm o i on-aluminum
ma e ial (16.87mg/g) demons a es ha phospho us locking agen
has a g ea e heo e ical abili y o cap u e phospho us a
equilib ium.
The F eundlich iso he m model is used o desc ibe adso p ion on a
su ace wi h non-uni o mly dis ibu ed adso p ion hea . Pa ame e s
KF (indica o o adso p ion capaci y) and 1/n (indica o o in ensi y
o adso p ion) a e used in he empi ical F eundlich equa ion. Fo
he phospho us locking agen , a F eundlich i ing yielded KF =
6.58 L/mg and n = 0.18, wi h R² = 0.67. The i on-aluminum alloys
had KF( L/mg) = 5.98, 1/n = 0.17 and R2 = 0.59. The coe icien 1
/n gi es us an idea o he a o abili y o adso p ion and su ace
he e ogenei y (Table 3). When 1/n lies be ween 0.1 and 0.5,
posi i e adso p ion alues a e obse ed, wi h lowe alues
indica ing mo e he e ogeneous su aces and s onge adso ben -
adso ba e in e ac ions (Anwa e al., 2024). The ex emely low 1/n
alues (0.17-0.18) in he ma e ials indica e ex emely desi able
adso p ion wi h s ong adhesion.
Table 3: Iso he m Model Pa ame e s o Phospho us Adso p ion
Ma e ial
Langmui Adso p ion Model
F eundlich Adso p ion Model
qm (mg/g)
kL (L/mg)
R²
KF (L/mg)
1/n
R²
Phospho us Locking Agen
25.06
0.09
0.98
6.58
0.18
0.67
I on-Aluminum Ma e ials
16.87
0.06
0.96
5.98
0.17
0.59
The signi ican ly be e i o he Langmui model (R² = 0.96) han
o he F eundlich model (R² = 0.67) demons a es ha a
p edominan ly monolaye adso p ion on compa a i ely
homogeneous su ace si es p e ails o e mul ilaye adso p ion o a
he e ogeneous su ace ela ionship (Table 3). This obse a ion
sugges s ha phospho us abso p ion occu s p ima ily h ough
chemical complexa ion wi h speci ic unc ional g oups on he
su ace, a he han adso p ion o a ious su ace si es. The poo i
wi h he F eundlich model is due o i s ailu e o explain he
sa u a ion aspec obse ed a high phospho us concen a ions in he
solu ion. The Langmui model, on he o he hand, is a good
p edic o o he app oach o maximum capaci y.
3.3 Ma e ial Phospho us Remo al E iciency
Compa ison
The combina ion o kine ic and Iso he mal indings e eals sub le
a ia ions in ma e ials based on expe imen al condi ions and
e alua ion pa ame e s. I on-aluminium ma e ials showed
signi ican ly be e esul s unde kine ic expe imen al condi ions,
e en a ai ly low ini ial phospho us concen a ions and sho
con ac imes, wi h an adso p ion capaci y o 18.35 mg/g compa ed
o only 3.69 mg/g o he phospho us locking agen (Table 4). This
ep esen s a i e imes g ea e e iciency o phospho us emo al
using i on-aluminium ma e ial unde mode a e ea men
condi ions wi h easonable h oughpu s and phospho us con en .
Howe e , unde iso he mal condi ions, when equilib ium is
eached, expe imen s e ealed ha capaci y is ela ed di e en ly as
he con ac ime inc eases. The phospho us locking eagen
heo e ically eached an adso p ion capaci y o 25.06mg/g unde
he Langmui model, which was be e han he maximum
adso p ion equency in i on-aluminium- ype subjec s o
16.87mg/g (Table 4). This appa en aspec o con adic ion o
kine ic and iso he mal esul s mus no be cons ued o be so. An
inc ease in he healing capaci y o a phospho us locking agen can
complica e i s ul ima e phospho us binding capaci y when i is
exposed o low le els o pe ec ly equilib a ing condi ions, and he
su ace is sa u a ed (Schumache e al., 2018). This heo e ical
maximum capaci y is, howe e , ha de o achie e in p ac ice. I
akes longe con ac imes o achie e, and i may no p o e help ul
in eal ea men applica ions.
The es ima ion o dec easing simila i ies be ween kine ic and
equilib ium capabili ies signals he impo ance o aking in o
accoun he mu ual in luence o he ma e and he a e o
de elopmen o he adso p ion p ocess, as well as he capaci y
de elopmen o he adso p ion p ocess in i s applica ion. The I on-
Aluminium media has been indica ed o be e ec i e in a high a e
o phospho us emo al, and impo an ly, a high capaci y, using low
con ac ime, which makes his ype o media applicable in
con inuous low ea men . E en hough phospho us locking agen s
can be used a a highe capaci y a equilib ium, hey can be quickly
ea ed only a a slowe a e, limi ing hei use o o he p ac ices
ha demand a apid ea men a e.
These di e ences in pe o mance a e due o mechanis ic
di e ences. I on-aluminium compounds a e also likely o be
loaded wi h high concen a ions o i on and aluminium
oxide/hyd oxide su aces composed o huge emissions o hyd oxyl
(-OH) g oups and unde go ligand swi ching wi h phospha e ions,
esul ing in s abilized inne -sphe e a acks o Fe-O-P and Al-O-P
addic ions. I is a way o apid and solid bonding o phospho us by
he e ec i e dispe sion o a chemical. Acco ding o Naza ian e al.
(2021), bo h aluminium and i on oxides ha e a s ong a ini y o
phospha e due o he o ma ion o monoden a e and biden a e
complexes on hei su ace, which is ela ed o he pseudo-second-
o de kine ics o he eac ion and he Langmui iso he m
ela ionships.
The mechanism unde which he phospho us locking agen wo ks
is p obably di e en and may in ol e chemical adso p ion and he
ion exchange p ocess. In comme cial phospho us locking
ma e ials, modes phospho us locking ma e ials a e used, and
a he han being a comple e na u al clay o a compound as ound
in na u e, hey a e modi ied clays o compounds o op imize
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DOI: 10.5281/zenodo.17339353
28
phospho us binding in a ious ways (Ewis e al., 2022). These
p oduc s may be ul ima ely well-ca ying, bu wi h a la ge numbe
o apidly oscilla ing molecules, adso p ion may ac ou wi h e en
mo e complex, mul iplica ed kine ics. Addi ionally, he
sensi i i ies o pH and he ole o o he compe ing ionic species
can ha e a g ea e in luence on he p ope ies o phospho us
locking agen s han hei coun e pa s manu ac u ed om i on-
aluminium p oduc s.
Table 4: Compa a i e Summa y o Phospho us Remo al Pe o mance
Pe o mance Me ic
Phospho us Locking Agen
I on-Aluminum Ma e ials
Supe io Ma e ial
Kine ic Capaci y (qm)
3.69 mg/g
18.35 mg/g
I on-Aluminum Ma e ials
Kine ic R² (Pseudo-Second-O de )
0.98
0.99
I on-Aluminum Ma e ials
Equilib ium Capaci y (qm, Langmui )
25.06 mg/g
16.87 mg/g
Phospho us Locking Agen
Equilib ium R² (Langmui )
0.98
0.96
Phospho us Locking Agen
Adso p ion Ra e Cons an (k₂)
0.47 g/(mg·min)
0.24 g/(mg·min)
Phospho us Locking Agen
P ac ical Applica ion Sui abili y
Mode a e
High
I on-Aluminum Ma e ials
4. Discussion
4.1 In luence o Ma e ial Cha ac e is ics on Phospho us
Remo al E iciency
I is possible o desc ibe high-le el phospho us adso p ion beha io
o i on-aluminium ma e ial in a kine ic expe imen using se e al
ma e ial ea u es. Speci ic su ace a ea is a c ucial pa ame e ha
de e mines he numbe o adso p ion si es. The esidues o wa e
a e ea men become i on-aluminium and no mally p oduce
ma e ials wi h high speci ic su ace a eas o he o de o 50-200
m²/g, which p o ide la ge su ace a eas o adso b phospha es.
Amo phous i on/aluminium oxides/hyd oxides a e also use ul in
p o iding a high eac i i y o he su ace. Unlike c ys alline me al
oxides wi h a egula su ace s uc u e, amo phous phases a e
cha ac e ized by a diso ganized a omic s uc u e, p o iding a
he e ogeneous coo dina ion en i onmen and de ec si es wi h a
high phospha e eac i i y capabili y.
The hyd oxyl g oups on he su aces o i on and aluminium oxides
play a signi ican ole in he phospha e adso p ion p ocess. The
su ace o he i on oxide and aluminum oxide a a ci cumneu al
pH acqui es a posi i e cha ge ollowing he p o ona ion o su ace
hyd oxyl ollowing he o ma ion o he oxide g oups. This epels
he nega i ely cha ged anions o phospha e (H2PO4-, HPO4²-) due
o he a ou able su ace cha ge, acili a ed by he elec os a ic
o ce, and allows o he educ ion o phospha e o su ace-ac i e
si es. Then, he e is he appea ance o a ligand exchange eac ion,
whe e he su ace hyd oxyl g oups/wa e molecules a e eplaced
wi h a phospha e, which binds di ec ly o he Fe-O-P o Al-O-P
bond (Gao e al., 2025). Spec oscopic s udies ha e con i med he
exis ence o monoden a e and biden a e complexes o phospha e on
i on and aluminium oxides, wi h he biden a e complexes being
mo e pe sis en han he monoden a e complexes.
I on and aluminium, which a e con ained in he wa e ea men
esiduals, ha e a di ec co ela ion wi h phospho us adso p ion
capaci y, as epo ed in se e al s udies. This s udy has ound s ong
co ela ions be ween oxala e-ex ac able aluminium and i on
concen a ions, and phospho us adso p ion capaci y, wi h
co ela ion coe icien s ypically exceeding 0.85, which aligns wi h
he indings o Rahma i e al. (2022). The i on-aluminium
ma e ials a e ich in he concen a es o hese me al oxides. These
ma e ials a e p epa ed using wa e wo k sludge, employing
aluminium and i on coagulan s, which is why hey ha e a high
phospho us binding capaci y. I is also a mola a io ha in luences
he pe o mance o adso p ion some esea ch sugges s ha i on-
aluminum assemblies may exhibi syne gies a an indi idual le el,
as well as join designa ion.
The d awback o he phospho us locking agen can be iden i ied
h ough di ec comple ion wi h he help o a compa a i e analysis.
T adeo s be ween cos , capaci y, and kine ics a e e iden in
comme cial phospho us locking p oduc s. A high-capaci y p oduc
design migh con ain high- alue componen s ha a e imp ac ical
o mass p oduc ion. Addi ionally, se e al phospho us apping
agen s exhibi high sensi i i y o pH, and some d as ically educe
adso p ion in he p esence o high alkalini y le els, such as in
eu ophic lakes. Such pH a ini y may pose a pe o mance p oblem
in na u al wa e sys ems wi h pH a ia ions a ei he he seasonal
o spa ial scale. The ela i e inc ease in sa u a ion o adso p ion
wi h ime in ou kine ic empe a u e expe imen s may be indica i e
o a low egene a ion po en ial unde ou kine ic empe a u e
condi ions o a ailu e o achie e con inuous ope a ion in a
cons an low sys em.
4.2 P ac ical Applica ion Feasibili y
Economic ac o s a e qui e o e whelming when conside ing he
use o i on-aluminum ma e ial as a p ima y wa e ea men
me hod. The esiduals o wa e ea men a e indus ial ypes o
was e ha need o be elimina ed a a cos o he ope a o s o he
wa e wo ks. The use o hese esiduals as an adso ben ma e ial o
pe o m phospho us adso p ion ans o ms an exis ing issue o
disposing o hese p oduc s in o a eco e y oppo uni y ha helps
educe was e and imp o e wa e quali y. The shunned disposal
expendi u es, plus he absen eeism o pu chasing adso ben
comme cials, signi ican ly make adso p ion- ype phospho us
ex ac ion economically iable. Zheng e al. (2022) es ima ed ha
using wa e ea men esiduals in phospho us ea men can help
sa e cos s by 40-60% compa ed o using a comme cial adso ben .
The use o i on-aluminum ma e ials is ano he en i onmen al
bene i . The p inciples o was e alo iza ion and esou ce eco e y
inhe en in he concep o he ci cula economy align wi h global
sus ainabili y objec i es. Ins ead o disca ding he esidues o
wa e ea men di ec ly in o land ills o dumping hem in o he
oceans, con e ing he esidues in o iable adso ben s inc eases
hei li espan and causes no ha m o he en i onmen . Mo eo e ,
i on-aluminum adso ben s ap phospho us, which is s able in
complex wi h he me al-phospha e and has low isks o leakage (Yi
e al., 2023). I can be e ec i ely abso bed as inal disposal o
possibly eco e ed by a special p ocess as phospho us. Some
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29
s udies ha e in es iga ed phospho us eco e y using sa u a ed
I on-aluminum adso ben s, ei he h ough acid eco e y o he mal
use, he eby de eloping a closed-loop phospho us cycle ecycling
sys em.
Field applica ions mus conside he en i onmen al lexibili y o
adso ben ma e ials in esponse o a ying en i onmen al
condi ions. The e ec s o empe a u e on adso p ion a e usually
endo he mic, esul ing in an inc ease in phospho us up ake wi h
inc eased empe a u e as he di usion a e inc eases, leading o a
heigh ened eac ion a e o chemical adso p ion (Kanwal e al.,
2024). Na u al wa e bodies, howe e , no mally exhibi changes in
empe a u e wi hin limi s, he magni ude o which is insigni ican .
Mo e impo an issues conce n he e ec s o coexis ing ions and
o ganic ma e . Sulpha e, ca bona e, silica e, and na u al o ganic
ma e a e some o he dissol ed species ound in na u al wa e s
ha can ei he compe e wi h o co e he su ace loca ions
adso bed by phospha e. Li e al. (2016) epo ed ha a high le els,
sul a e compe i i ely adso bs o he phospha e adso ben o i on-
aluminum oxides. Ca bona e and bica bona e ions also compe e
wi h phospha e, especially a alkaline pH, whe e ca bona e
specia ion a o s ca bona e ions.
The in e ac ions be ween na u al o ganic ma e (NOM) and i on-
aluminum adso ben s a e complex and, in some cases,
con adic o y. Kim and Jang (2017) sugges ha NOM adso bs
on o he su aces o i on-aluminum oxide, p e en ing si es and
deple ing he i on-aluminum oxide phospha e adso p ion capaci y.
Howe e , Bligh e al. (2017) epo ha NOM can s abilize
amo phous i on oxides agains aging and c ys alliza ion, he eby
main aining high su ace eac i i y o e a long pe iod. E en in ou
d inking wa e , ea ed i on-aluminum ma e ials exhibi a
cha ac e is ic whe e he sou ce wa e lea es behind NOM. In ac ,
i could be he cause o hei consis en pe o mance. The o e all
impac o NOM will mos likely be dependen on i s concen a ion,
composi ion, and dis ibu ion o molecula weigh s. The
hyd ophobic NOM ac ions wi h a oma ic s uc u es can be easily
adso bed o block si es. In con as , he hyd ophilic ac ions wi h
high ca boxyl g oups can complex wi h i on/aluminum, lea ing he
emaining hyd oxyl g oups ee on he su ace o bind phospha es.
The opic o long- e m s abiliza ion and egene a ion is wo h
explo ing in he con ex o sus ainabili y applica ions. I on-
aluminum alloys a e highly esilien unde no mal en i onmen al
condi ions. The close in e ac ion be ween phospha e and
i on/alumina oxide esul s in high inne -sphe e complexa ion,
leading o essen ially i e e sible binding a ci cumneu al pH. The
phospho us elease o i on-aluminum adso ben unde deso p ion
condi ions has been obse ed o be low a e p olonged in e ac ions
wi h wa e , suppo ing he ac ha i is no p one o leaching. This
is a bene i o pe manen phospho us emo al applica ions, such as
capping aqua ic sedimen s in lakes o we land il e s. S ong
binding is a limi e in applica ions whe e he adso ben s a e
equi ed o be egene a ed. In such cases, solu ions o alkaline (pH
> 11) o acidic sequences a e gene ally used in he egene a ion
p ocess, which can damage he adso ben s uc u e o e nume ous
cycles. Fu he inno a ion can be done by de eloping mo e eadily
egene able i on-aluminum ma e ials by su ace modi ica ion.
Table 5: Compa ison o Phospho us Adso p ion Capaci ies Ac oss Di e en Adso ben Ma e ials
Adso ben Ma e ial
Adso p ion Capaci y (mg P/g)
Op imal pH
Con ac Time
Re e ence/Sou ce
I on-Aluminium Ma e ials (This S udy)
18.35 (kine ic)
~7
2-3 h
Cu en S udy
Phospho us Locking Agen (This S udy)
3.69 (kine ic)
~7
24 h
Cu en S udy
Al-based Wa e T ea men Residuals
7.7-12.5
6-7
24 h
Mak is e al., 2004
Fe-based Wa e T ea men Residuals
9.1-11.4
3-6
24 h
Day on & Bas a, 2005
Modi ied Palygo ski e
8.2
5
8 h
Ye e al., 2006
Lan hanum-Modi ied Ben oni e
52.6
5-9
4 h
Zampa as e al., 2012
Red Mud
15.8
3-5
6 h
Huang e al., 2008
Alum Sludge
6.6
6
24 h
Yang e al., 2006
4.3 Resea ch Limi a ions and Fu u e Di ec ions
The e a e se e al limi a ions associa ed wi h his s udy. The
expe imen s used simpli ied ba ch sys ems, which used a i icial
phospha e solu ions as opposed o he eal wa e body. Na u al
wa e s possess hund eds o dissol ed cons i uen s and pa icula es,
which can ha e adso p ion e ec s. Simula ion o con inuous low
condi ions in columns would o e be e pe o mance in o ma ion
on ea ing sys em design. Also, kine ic and Iso he m expe imen s
we e pe o med and had compa a i ely small ime scales (hou s o
days), bu as in p ac ice, weeks o mon hs a e ope a i e. The
sus ainabili y o ma e ial pe o mance would be es ed h ough
long- e m s abili y ield es ing.
The seemingly measu ed dispa i y be ween kine ic and Iso he m
capaci ies is a subjec ha needs u he esea ch. Fu u e s udies
mus expe imen ally sweep ini ial phospho us concen a ions,
con ac ime, and solid- o-liquid a io o co e he pe o mance
pa ame e space ully. This would allow he o ecas ing o any
op imal ope a ing condi ions used in pa icula cases o ea men .
The highly de eloped me hods o cha ac e iza ion, which p o ed
o be X- ay pho oelec on spec oscopy (XPS), scanning elec on
mic oscopy (SEM), and Fou ie ans o m in a ed spec oscopy
(FTIR), would be use ul o access mechanis ic in o ma ion in
phospha e binding modes and specia ion al e a ion on he su ace
du ing he adso p ion p ocess.
The app oaches o ma e ial modi ica ion p o ide an oppo uni y
o u u e imp o emen s in he pe o mance o phospho us locking
agen s. The posi ion o he phospho us locking ma e ials in he
lan hanum d awing o phospha e has been he ocus o in e es in
lan hanum due o he high a ini y o he phospha e and lan hanum
o p oduce he highly insoluble lan hanum phospha e p oduc .
Resea ch has indica ed ha phospho us adso p ion capaci ies on
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DOI: 10.5281/zenodo.17339353
30
lan hanum-modi ied ben oni es o o e 50 mg/g ha e been
eco ded, which is signi ican ly mo e when compa ed o he
unmodi ied coun e pa s. None heless, he p ice o lan hanum and
i s possible eco oxici y ha e o be conside ed closely. O he la o s
o changes in ol e su ace coa ing he polyme s so as o enhance
he densi y o he hyd oxyl g oups on he su ace, he mal
ea men in o de o maximize he po osi y and c ys allini y, o by
in eg a ing wo o mo e unc ional pa s in o a composi e ma e ial.
The sys ema ic s udy o e ec s o modi ica ion on bo h capaci y
and kine ics would help in designing a new gene a ion o
phospho us adso ben s.
Some enginee ing issues need o be add essed when scaling down
a labo a o y implemen a ion o a ield implemen a ion. Adso ben
deploymen condi ions need o s ike a balance in con ac
pe o mances, p essu e d op, and unc ionali y. Fixed-bed columns
a e easy o ope a e, bu hey can gene a e clogging and channeling.
Fluidized bed sys ems ha e good con ac ; howe e , hese sys ems
demand mo e complica ed hyd aulics. In-si u sedimen loading
using adso ben s du ing sedimen applica ion p o es o be
p omising, bu equi es e en dis ibu ion and ensu es he p edic ion
o he long- e m pe o mance o adso ben s. P e-pilo ield es s, in
selec ed wa e ea men plan s, would be ins umen al in he
echnology es and deepening be o e ull-scale ea men is
adop ed.
5. Conclusion
This compa a i e s udy o phospho us elimina ion e icacy
be ween phospho us locking ma e ial and ai aluminium ma e ials
p esen ed se e al essen ial esul s ha possessed heo e ical and
ins umen al ou comes. When he i on-aluminum ma e ials
ope a ed unde kine ic expe imen al condi ions a ibu ed o
phospho us adso p ion abili y, i was ound ha hey possessed a
supe io phospho us adso p ion capaci y o 18.35mg/g in
compa ison o he phospho us locking agen , which has a lowe
capaci ance o jus 3.69mg/g. Bo h subs ances ga e excellen
co ela ion wi h pseudo-second-o de kine ic models (R2 > 0.98),
and he sensi i i y o he a e-limi ing s ep o phospho us up ake
was ound o be chemical adso p ion. The pseudo-second-o de
eac ion sugges s ha he e is an exchange o ans e o elec ons
be ween he phospha e ions and he su ace o he adso ben and
si es, as pe he ligand exchange and o ma ion o inne -sphe e
complexes.
Iso he m analysis showed ha bo h es ed ma e ials comply well
wi h he Langmui model (R2 >0.96), which implies ha adso p ion
on he ma e ials is on monolaye si es o he ela i ely
homogeneous su ace. Al hough he phospho us locking agen had
a highe cons an maximum capaci y unde Langmui i ing (25.06
e sus 16.87 mg/g), he bene i was only obse ed o e longe
equilib a ion e ms, which would no be ypical o he ea men
p ocess. I on-aluminum ma e ial is be e placed in espec o he
eal-li e usage o he solu ion because o he highe kine ic
pe o mance, as i is use ul in eal-li e si ua ions when phospho us
has o be emo ed quickly wi hin easonable con ac imes.
Mechanis ic knowledge was achie ed by combining kine ic and
Iso he m knowledge wi h he cha ac e iza ion o he ma e ial. The
main mechanism is chemical adso p ion, in which he su aces o
i on-aluminum ma e ials, con aining high con en s o he hyd oxyl
g oup, p omo ed he ligand exchange eac ions wi h phospha e.
The ea s o s able Fe-O-P and Al-O-P bonds by biden a e su ace
complexa ion a e he soli a y basis o ele a ed po ency phospho us
connec ing. Such a chemical e en is he explana ion o apid
kine ics and high binding alues in he expe imen .
Th ough he indings, we would speci y he use o i on-aluminum
ma e ials o phospho us emo al in si ua ions o bi- eac ion on
high-concen a ion phospho us-con amina ed bodies o wa e . The
high in ensi y wi h as dynamics, low cos wi h mo ning o was e
alo iza ion, and sus ainabili y o he en i onmen al app oach used
make i on-aluminum ma e ials he bes choices as adso ben s. I is
ecommended ha u u e s udies should seek o op imize he
p epa a ion p ocedu es o accomplish he maximum su ace a ea
and hyd oxyl g oup densi y, he pe o mances a a ious condi ions
unde ou lay ci cums ances using ealis ic wa e ma ices, and how
hey can be scaled o implemen hem in he ield. Ne e heless, in
e ms o u he pu i ica ion, he echnology o i on-aluminum
ma e ials can be p omising in sol ing he in e na ional issue o
phospho us pollu ion and eu ophica ion in wa e bodies.
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