Kinetics and isotherm of cadmium adsorption onto polyethylene microbeads in artificial seawater

Abstract

This study investigates the interactions between cadmium (Cd) and microplastic under controlled laboratory conditions using low density polyethylene microbeads as model of plastic particles. Cadmium was added to suspensions of artificial seawater to investigate heavy metal adsorption on microbeads surface in five different concentration. Polyethylene microbeads proved to have affinity in providing surface area for cadmium. Microbeads served as an effective sorption surface and concentrated cadmium amount in seawater through adsorption process. The maximum adsorption was monitored for 96 hours. Maximum adsorption capacity determined to be 0.0101 mg/g occurring within 12-48 hours in test concentration. While, kinetic study was performed according to pseudo-first-order kinetic with kd at 0.011 L/g. Using data from pseudo first order, isotherm study was performed in nonlinear regression and dataset was in good agreement with Langmuir, Freundlich and Redlich Petterson with coefficient of determination at 0.865, 0.964 and 0.962 respectively. Adsorption of cadmium to polyethylene microbeads has important implications for the potential role of microplastics, in this case microbeads-cadmium contaminated act as a quantified link in aquatic food webs.