Enhanced Adsorptive Removal of Cd (II) from Aqueous Solution Using a Rhamnolipid Biosurfactant-Activated Carbon Biocomposite

In this research study, the adsorption properties of a pistachio shell-derived activated carbon composited with rhamnolipid biosurfactant produced from Pseudomonas aeruginosa bacteria have been investigated for the removal of heavy metals from aqueous environments. For this purpose, following the production and characterization of the biocomposite, the effect of some important operational parameters, including the ratio of biocomposite to metal, initial solution pH and the agitation rate, on the efficiency of cadmium removal was evaluated in the form of a response surface experimental design (RSM), central composite (CCD) type. After optimizing the process, other aspects of the process including kinetics, thermodynamics, isothermal adsorption, multistep adsorption and selectivity were also investigated. The results of the statistical analysis of the experimental design indicated that the influence of the biocomposite to metal ratio and solution pH on the adsorption efficiency is significant and increasing. Moreover, although the effect of agitation rate was insignificant, its interaction with other operating parameters was substantial. The optimization of the process also showed that under the optimal conditions of biocomposite to metal ratio of ۲۰۰, solution pH of ۱۰ and agitation rate of ۳۰۰ rpm, removal efficiency of more than ۹۷% can be achieved. Kinetic studies revealed that the process of cadmium adsorption on the biocomposite surface follows a pseudo-second-order process with a fast kinetic rate of ۶۵.۴۱ g/mg.h. The results of thermodynamics, isothermal adsorption and multistep adsorption evaluations also demonstrated that the adsorption process followed a fast chemical mechanism up to ۱۰ min following a very slow process, possibly precipitation. Furthermore, selectivity studies revealed that the presence of other heavy metals significantly influenced the adsorption efficiency. Generally, the findings of the present research study demonstrated the promising applicability of rhamnolipid/activated carbon biocomposite as an efficient sorbent for heavy metal removal from contaminated aqueous environments.

کلیدواژه ها:

Rhamnolipid biosurfactant ، Activated Carbon ، Biocomposite ، Wastewater ، Adsorption mechanism ، Selectivity index