Modified Oil Palm Biomass-Based Adsorbent for Cadmium Removal: A Review

Abstract

Cadmium pollution in some of Malaysia's rivers and the discovery of cadmium in some edible aquatic species from the rivers were quite alarming because of how quickly this toxic substance can spread into the human body through contaminated food that later damages the human organs. The biomass disposal problem is another major issue that Malaysia is facing as the second-largest producer of palm oil worldwide. The utilization of oil palm biomass into cadmium adsorbent can solve the oil palm biomass disposal issue and cadmium pollution issue at the same time. Several studies on cadmium adsorption by different types of oil palm biomass in the forms of raw, charcoal, biochar, hydrochar, activated carbon, nanomaterials, and composite adsorbents have been reported in recent studies. The adsorbent modifications discussed in this review focused on five methods; combustion, gasification, hydrothermal carbonization, acid and alkali, and polymer grafting. Among the modification methods, the output of polymer grafting of deoiled palm kernel cake (DOPC) produced adsorbent with high Cd2+ removal efficiency of 99%. This review is to help the progress of modification technologies for different types of oil palm biomass so that proper selection of effective treatment methods can be achieved.