ADSORBENT CHARACTERISTICS ADSORBENT CHARACTERISTICS & ADSORPTION MECHANISMS Muhammad Abbas Ahmad Zaini, PhD, CEng Centre of Lipids Engineering & Applied Research UTM Johor Bahru UTM Johor Bahru
ADSORBENT CHARACTERISTICSADSORBENT CHARACTERISTICS& ADSORPTION MECHANISMS
Muhammad Abbas Ahmad Zaini, PhD, CEngCentre of Lipids Engineering & Applied Research UTM Johor BahruUTM Johor Bahru
OBJECTIVE
Sharing the research outcomes in relation to Sharing the research outcomes in relation to
adsorbent characteristics and adsorption
h i mechanisms.
Findings from 2009 to 2017; laboratory prepared
adsorbents/activated carbons for dyes and heavy
metals removal from watermetals removal from water.
OUTLINE
Adsorbent characteristics: An overviewAdsorbent characteristics: An overview
Case 1: Mesoporosity & microporosity
Case 2: Degassed activated carbon
Case 3: Specific surface area
Case 4: Functional groupsg p
Case 5: Changes in surface acidity
ADSORBENTSolid materials – natural or synthesized –with affinity towards certain solutes or molecules.
Rich in functional groups and/or well-developed porous textures. Performance may vary.
Mechanisms of removal: specific surface area-sensitive (roles of pore volume, mesoporosity, microporosity), surface functional groups (acidic or basic groups) ion exchange π π(acidic or basic groups), ion exchange, π-πinteraction, changes in surface charge.
CHARACTERISTICS OF ADSORBENT
Textural properties specific surface area pore Textural properties – specific surface area, pore
volume, microporosity, mesoporosity (BET method).
Surface functional groups – acidic and basic groups,
cationic exchange capacity (Boehm titration,
Ammonium acetate/methylene blue method, pH,
pHPZC FTIR)pHPZC, FTIR).
Others: thermal, proximate and ultimate analyses.
BOEHM TITRATION
(Agricultural Research Updates Vol. 6, 2013)
CATTLE-MANURE-COMPOST BASEDACTIVATED CARBONS
A residue of temperature phased anaerobic digestion A residue of temperature-phased anaerobic digestion
for methane generation.
Carbonaceous material; precursor for activated
carbon.
One-step ZnCl2-activation under N2 flow at 500°C for
1 h1 h.
CASE 1: MESOPOROSITY & MICROPOROSITY
ZnCl2-activated cattle
manure compost carbons manure compost carbons
for Cu(II) adsorption.
Specific surface area;
mesopore-rich carbon.
(J Hazard Mater 170, 2009)
CASE 2: DEGASSED ACTIVATED CARBONS
Degassing of nitrogen-rich activated carbons for Cu(II) and Pb(II) adsorption.
π-cation interaction becomes operative for both metals ions.
Insignificant effect of surface area and pore volume for Cu(II) removal.
(TANSO 234, 2008)
CASE 2: (CONT’D)Increasing degassing
temperature decreases e-
withdrawing groups.
For carbons with similar
textural properties Pb(II) textural properties, Pb(II)
removal increased after
degassing.
(Desal Water Treat 52, 2014)
CASE 2: (CONT’D)
Surface affinity for Cu(II) adsorption increased after degassing.
However, the removal decreased because the mesopores have been resided by protons.
(Desal Water Treat 51, 2013)
EMPTY FRUIT BUNCH- & PALM KERNELSHELL-BASED ACTIVATED CARBONS
By chemical activation using chloride saltsBy chemical activation using chloride salts.
Activated carbons-derived from PKS via microwave-
assisted activation.
For dyes removal from waterFor dyes removal from water.
Attempt to recover activating agent for subsequent
activation.
CASE 3: SPECIFIC SURFACE AREA
Direct correlation of
rhodamine B maximum
adsorption (qmax) with adsorption (qmax) with
specific surface area, R2 =
0 9930.993.
Activated carbons by
chloride salts activation
are generally mesoporous.
(HJIC, in press)
CASE 3: (CONT’D)
PKS-based activated carbons for column adsorption of methylene blue.
Specific surface area decreased from 858 to 345 m2/g; gap in adsorption capacity increased at higher concentration.
(Sains Malaysiana 43, 2014)
SLUDGE-BASED ADSORBENTS
The as received sludge from palm oil mill effluent The as-received sludge from palm oil mill effluent,
biopolishing sludge, yarn processing factory and oil-
i h l drich sludge.
Chemically- and thermally-treated, and untreated
sludge sorbents for dyes and heavy metals removal
from water from water.
CASE 3: (CONT’D)
(Energy Procedia 61, 2014)
CASE 3: (CONT’D)Anaerobic sludge and g
biopolishing sludge.
I d ifi Increased specific
surface area after acid
treatment has positive
effect on methylene
blue removal.
(Desal Water Treat 52, 2014)
CASE 4: FUNCTIONAL GROUPS
Z Cl h d th ffi it f th l bl d it b i th b t ZnCl2 enhanced the affinity for methylene blue despite being the sorbent with lowest surface area.
HCl and some chemical agents diminished the active sites for adsorption.
(PJST 18, 2016)
g p
Untreated sludge is a promising dye sorbent.
CASE 4: (CONT’D)
Simple chemical treatment against no treatment on yarn processing sludgeprocessing sludge.
Interactions via functional groups are relatively strong.
(Chiang Mai J Sci 44, 2017)
Untreated sludge is a promising dye sorbent.
CASE 5: CHANGES IN SURFACE ACIDITY
Removal of Pb(II) increased with equilibrium pH.
The surface becomes e su ace beco es deprotonated, dissociation of protons.p
The acidic oxygen functional groups dominating the groups dominating the negatively charged surface for cations adsorption
(J Hazard Mater 170, 2009)
cations adsorption.
CASE 5: (CONT’D)Removal of methylene blue by y y
human hair sorbent.
H d d d i f 12141618
y, q
e (m
g/g) 5 mg/L
10 mg/L
pH-dependent adsorption for
higher dye concentration.468
10
mov
al c
apac
ity
02
0 5 10 15
Rem
pHpH
(Green Proc. Synth., submitted)
CONCLUSION
Characteristics of sorbents may vary depending on Characteristics of sorbents may vary depending on
sources and preparation strategies.
Performance of sorbents for water pollutants
removal could be a function of multiple
characteristics.
S ifi f d f h i Specific surface area and surface chemistry are
commonly associated with the performance of
sorbents.