Technical Control of Cd2+ from the Sludge Utilizing Cashew Nutshell Liquid Based Micron-Sized Polymeric Particles

Abstract

This study investigated the effectiveness of micron-sized polymeric particles derived from Cashew Nutshell Liquid (CNSL) in removing cadmium cations from a laboratory-scale aquatic environment. The researchers synthesized hydroxyl-functionalized polymer particles using the emulsion polycondensation technique, with sizes ranging from 0.1 µm to 0.4 µm confirmed by Transmission Electron Microscopy (TEM). Cryo-Scanning Electron Microscopy (cryo-SEM) revealed their distinctive spherical morphology with a yellowish-brown hue. Chemical modifications (carboxylation, sulfonation, and aminopropylsilation) were achieved and confirmed through infrared (IR) spectra analysis. Atomic Absorption Spectrophotometry (AAS) evaluated the cadmium exchanging capacities of both original and modified micron-sized polymer particles in column reactions, and regeneration methods were employed for particle reusability. Unmodified and modified particles displayed substantial cadmium exchanging capacities, influenced by pH and elution rates. Modified particles, particularly sulfonated and carboxylated ones, outperformed unmodified counterparts in cadmium ion exchange. For instance, unmodified resin exchanged 0.034 mg/g, while sulfonated and carboxylated resins exchanged 0.051 mg/g and 0.093 mg/g of cadmium ions, respectively. The optimal pH for cadmium uptake was established at 4. Regenerated resins exhibited lower cadmium exchange compared to fresh resins at pH 4 and pH 6. Flow rates of influent solution and resin packing density significantly affected cation uptake. The study advocates for further research to scale up the application of CNSL-based micron-sized polymer particles for controlling heavy metal pollution in authentic aquatic environments.