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 (NRL/PVA) nanofibre matrix to remove Cd²⁺ from aqueous solution was examined. Electrospun AgNP-NRL/PVA 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 different reaction times of 20 min for 0.01 M AgNP and 40 min for 0.015 M AgNP. The maximum adsorption for 0.01 M AgNP was 14.9674 mg/g and 30.1129 mg/g for 0.015 M AgNP. 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 having a lower desorption constant and larger boundary layer (β = 0.1793 g/mg; C = 7.5959 mg/g) than 0.01 M AgNP (β = 1.0351 g/mg; C = 4.5942 mg/g). 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 process, silver (Ag) concentration in the treated water (0.01 M AgNP = 0.0425 mg/L, 0.015 M AgNP = 0.0510 mg/L) 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 NRL/PVA nanofibre matrix to remove contaminants (Cd²⁺) from contaminated water.