title: Silkworm exuviae--a new non-conventional and low-cost adsorbent for removal of methylene blue from aqueous solutions.
abstract: In this paper, silkworm exuviae (SE) waste, an agricultural waste available in large quantity in China, was utilized as low-cost adsorbent to remove basic dye (methylene blue, MB) from aqueous solution by adsorption. Kinetic data and sorption equilibrium isotherms were carried out in batch process. The adsorption kinetic experiments revealed that MB adsorption onto SE for different initial dye concentrations all followed pseudo-second order kinetics and were mainly controlled by the film diffusion mechanism. Batch equilibrium results at different temperatures suggest that MB adsorption onto SE can be described perfectly with Freundlich isotherm model compared with Langmuir and D-R isotherm models, and the characteristic parameters for each adsorption isotherm were also determined. Thermodynamic parameters calculated show the adsorption process has been found to be endothermic in nature. The analysis for the values of the mean free energies of adsorption (E(a)), the Gibbs free energy (ΔG(0)) and the effect of ionic strength all demonstrate that the whole adsorption process is mainly dominated by ion-exchange mechanism, which has also been verified by variations in FT-IR spectra and pH value before and after adsorption and desorption studies. The results reveal that SE can be employed as a low-cost alternative to other adsorbents for MB adsorption.
authors.affiliation: School of Pharmaceutical and Chemical Engineering, Taizhou University, Dongfang Road No. 605, Linhai 317000, Zhejiang, PR China. chenhao2212@sohu.com
authors.forename: Hao
authors.initials: H
authors.lastname: Chen
authors.forename: Jie
authors.initials: J
authors.lastname: Zhao
authors.forename: Guoliang
authors.initials: G
authors.lastname: Dai
mesh_terms: D000327:Adsorption; D000465:Algorithms; D000818:Animals; D012831:Bombyx / Q000737:chemistry*; D006813:Humidity; D006863:Hydrogen-Ion Concentration; D007220:Industrial Waste / Q000032:analysis*; D007700:Kinetics; D008751:Methylene Blue / Q000302:isolation & purification*; D012996:Solutions; D017550:Spectroscopy, Fourier Transform Infrared; D013816:Thermodynamics; D014867:Water; D014874:Water Pollutants, Chemical
chemical_list: D007220:Industrial Waste; D012996:Solutions; D014874:Water Pollutants, Chemical; D014867:Water; D008751:Methylene Blue