Study of Adsorption Characteristics of Cadmium into Chitosan biopolymer to be used for waste water treatments

Abstract

Pollution by heavy metals is a serious threat to aquatic ecosystems because some of these metals are potentially toxic even at very low concentrations. Chitosan, a biopolymer produced from crustacean shells, has applications in various areas, particularly in drinking water and wastewater treatment due to its ability to remove metallic ions from solutions. The purpose of this research work was to study the adsorption of cadmium on chitosan produced from shrimp shells at a laboratory level. Chitosan, with a degree of deacetylation of approximately 70%, was used in the experimental part and the flake sizes were smaller than 0.25mm. Experimental work involved the determination of the adsorption isotherms for each metallic ion in a batch system. The resulting isotherms were fitted using Langmuir model and the parameters of the equation were determined. Kinetic studies of adsorption for metallic ions at different concentrations and with different particle sizes were performed in batch system. Simplified models such as pseudo-first-order, pseudo-secondorder, and intra-particle diffusion equations were used to determine the rate controlling step. The results showed that the adsorption capacity depends strongly on pH and on the species of metallic ions in the solution. Batch adsorption experiments were performed at two differentdegrees of deacetylation (DD) values, time period ranging from 15 minutes to 3 hours and pH of solutions ranging from 3 to 7. The study showed that the solution pH strongly affects the adsorption capacity of chitosan.