Equilibrium and kinetic mechanisms of woody biochar on aqueous glyphosate removal.
We investigated the removal of aqueous glyphosate using woody (dendro) biochar obtained as a waste by product from bioenergy industry. Equilibrium isotherms and kinetics data were obtained by adsorption experiments. Glyphosate adsorption was strongly pH dependent occurring maximum in the pH range of 5-6. The protonated amino moiety of the glyphosate molecule at this pH may interact with π electron rich biochar surface via π-π electron donor-acceptor interactions. Isotherm data were best fitted to the Freundlich and Temkin models indicating multilayer sorption of glyphosate. The maximum adsorption capacity of dendro biochar for glyphosate was determined by the isotherm modeling to be as 44 mg/g. Adsorption seemed to be quite fast, reaching the equilibrium <1 h. Pseudo-second order model was found to be the most effective in describing kinetics whereas the rate limiting step possibly be chemical adsorption involving valence forces through sharing or exchanging electrons between the adsorbent and sorbate. The FTIR spectral analysis indicated the involvement of functional groups such as phenolic, amine, carboxylic and phosphate in adsorption. Hence, a heterogeneous chemisorption process between adsorbate molecules and functional groups on biochar surface can be suggested as the mechanisms involved in glyphosate removal.
Chemical and Environmental Systems Modeling Research Group, National Institute of Fundamental Studies, Kandy, Sri Lanka.
S S
SS
Mayakaduwa
Chemical and Environmental Systems Modeling Research Group, National Institute of Fundamental Studies, Kandy, Sri Lanka.
Prasanna
P
Kumarathilaka
Chemical and Environmental Systems Modeling Research Group, National Institute of Fundamental Studies, Kandy, Sri Lanka.
Indika
I
Herath
Soil Sciences Department, College of Food and Agriculture Sciences, King Saud University, Riyadh, Saudi Arabia.
Mahtab
M
Ahmad
Soil Sciences Department, College of Food and Agriculture Sciences, King Saud University, Riyadh, Saudi Arabia.
Mohammed
M
Al-Wabel
Korea Biochar Research Center, Department of Biological Environment, Kangwon National University, Chuncheon 200-701, South Korea.
Yong Sik
YS
Ok
Soil Sciences Department, College of Food and Agriculture Sciences, King Saud University, Riyadh, Saudi Arabia.
Adel
A
Usman
Industrial Physchology, College of Education, King Saud University, Riyadh, Saudi Arabia.
Adel
A
Abduljabbar
Chemical and Environmental Systems Modeling Research Group, National Institute of Fundamental Studies, Kandy, Sri Lanka. Electronic address: meththikavithanage@gmail.com.
Meththika
M
Vithanage
D000327:Adsorption; D002606:Charcoal / Q000737:chemistry*; D007887:Fabaceae / Q000737:chemistry*; D005998:Glycine / Q000031:analogs & derivatives* / Q000737:chemistry; D006540:Herbicides / Q000737:chemistry; D007700:Kinetics; D014865:Waste Disposal, Fluid / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D014934:Wood; D000097797:Glyphosate
D002606:Charcoal; D005998:Glycine; D006540:Herbicides; D014874:Water Pollutants, Chemical; D000097797:Glyphosate; C540010:biochar
Adsorption capacity; Bioenergy; Chemisorption; Functional groups; Herbicide