title: Kinetic and isotherm modeling of Cd (II) adsorption by L-cysteine functionalized multi-walled carbon nanotubes as adsorbent.
abstract: In this study, multi-walled carbon nanotubes were functionalized by L-cysteine to show the kinetic and isotherm modeling of Cd (II) ions onto L-cysteine functionalized multi-walled carbon nanotubes. The adsorption behavior of Cd (II) ion was studied by varying parameters including dose of L-MWCNTs, contact time, and cadmium concentration. Equilibrium adsorption isotherms and kinetics were also investigated based on Cd (II) adsorption tests. The results showed that an increase in contact time and adsorbent dosage resulted in increase of the adsorption rate. The optimum condition of the Cd (II) removal process was found at pH=7.0, 15 mg/L L-MWCNTs dosage, 6 mg/L cadmium concentration, and contact time of 60 min. The removal percent was equal to 89.56 at optimum condition. Langmuir and Freundlich models were employed to analyze the experimental data. The data showed well fitting with the Langmuir model (R2=0.994) with q max of 43.47 mg/g. Analyzing the kinetic data by the pseudo-first-order and pseudo-second-order equations revealed that the adsorption of cadmium using L-MWSNTs following the pseudo-second-order kinetic model with correlation coefficients (R2) equals to 0.998, 0.992, and 0.998 for 3, 6, and 9 mg/L Cd (II) concentrations, respectively. The experimental data fitted very well with the pseudo-second-order. Overall, treatment of polluted solution to Cd (II) by adsorption process using L-MWCNT can be considered as an effective technology.
authors.affiliation: Department of Environmental Health Engineering, Faculty of Health, Zabol University of Medical Sciences, Zabol, Iran.
authors.forename: Mahmoud
authors.initials: M
authors.lastname: Taghavi
authors.affiliation: Department of Environmental Health Engineering, Faculty of Health and Health Sciences Research Center, Mazandaran University of Medical Sciences, Sari, Iran. zazoli49@yahoo.com.
authors.forename: Mohammad Ali
authors.initials: MA
authors.lastname: Zazouli
authors.affiliation: Department of Environmental Health Engineering, Faculty of Health and Health Sciences Research Center, Mazandaran University of Medical Sciences, Sari, Iran.
authors.forename: Zabihollah
authors.initials: Z
authors.lastname: Yousefi
authors.affiliation: Food & Drug Laboratory Research Center, Food & Drug Organization, Ministry of Health and Medical Education, Tehran, Iran.
authors.forename: Behrouz
authors.initials: B
authors.lastname: Akbari-adergani
mesh_terms: D000327:Adsorption; D002104:Cadmium / Q000737:chemistry; D003545:Cysteine / Q000737:chemistry*; D052918:Environmental Restoration and Remediation / Q000379:methods; D007700:Kinetics; D008956:Models, Chemical; D037742:Nanotubes, Carbon / Q000737:chemistry*
chemical_list: D037742:Nanotubes, Carbon; D002104:Cadmium; D003545:Cysteine
keywords: Adsorption; Cadmium; Carbon nanotube; Isotherm modeling; L-MWCNTS