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.