Removal of Cadmium by Silver Nanoparticles Incorporated in Electrospun Natural Rubber Latex/Polyvinyl Alcohol Matrix

Abstract

In this study, the efficiency of silver nanoparticles (AgNP) incorporated into electrospun natural rubber latex/polyvinyl alcohol (PVA/NRL) nanofibre matrix to remove Cd from aqueous solution was examined. Electrospun AgNP-PVA/NRL nanofibre composites were produced using silver nitrate (AgNO₃) concentrations of 0.01 M and 0.015 M. Maximum Cd²⁺ was adsorbed at pH 7 for both nanofibre composites but at 20 min for 0.01 M AgNP (14.9674 mg/g; 11.90%) and 40 min for 0.015 M AgNP (30.1129 mg/g; 35.92%). Adsorption data were tested with Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherms as well as pseudo-first order (PFO), pseudo-second order (PSO), Elovich and intra-particle diffusion kinetic models. Cadmium adsorption by both nanofibre composites fitted best to Freundlich isotherm. Adsorption data for 0.01 M AgNP fitted best to PFO kinetic model, whilst that of 0.015 M AgNP fitted best to Elovich kinetic model, with 0.015 M AgNP (? = 0.1793 g/mg; C = 7.5959 mg/g) having a lower desorption constant and larger boundary layer than 0.01 M AgNP (? = 1.0351 g/mg; C = 4.5942 mg/g). However, the weak fit of the adsorption data for 0.01 M AgNP to all adsorption kinetic models used in the study implied that the experiment should be cut short at 20 min or extended beyond the experiment’s time frame. The nanofibre, 0.015 M AgNP, fitting best to Freundlich isotherm and Elovich kinetic model, showed that Cd²⁺ was chemisorbed. In general, 0.015 M AgNP was more efficient in adsorbing Cd²⁺ than 0.01 M AgNP. After the adsorption experiment, silver (Ag) concentration in the treated water was below US EPA and WHO guidelines of 0.10 mg/L for both nanofibre composites, rendering the treated water good enough for human use. Therefore, this work has shown the potential of AgNP incorporated in an electrospun PVA/NRL nanofibre matrix to remove contaminants (Cd) from contaminated water.