Modification of kelp and sludge biochar by TMT-102 and NaOH for cadmium adsorption

Abstract Cadmium (Cd) is a toxic heavy metal and has been recognized to be teratogenic and carcinogenic to human. Although different biochars have been developed for cadmium adsorption, interactions between the modification process and biochars’ pore structure, as well as their effect on heavy metal adsorption capacity have been overlooked. By using trithiocyanuric acid trisodium salt (TMT-102) and NaOH soaking, cadmium adsorption by non-porous sludge and porous kelp biochar were compared. The modified biochars were characterized by SEM, FTIR, BET, EDS and Zeta potential analysis, while their performance were evaluated under various adsorption time, pH and with the existence of coexisting ions. The results proved that TMT-102 modification could enlarge sludge biochar's surface area and improve its adsorption capacity significantly. It also suggests that TMT-102 modification is more suitable for non-porous sludge biochar than porous kelp biochar. The results also suggest that Ca2+, Mg2+, C5H7O5COO− and CH3COO− could reduce Cd removal efficiency significantly, suggesting the necessity of considering interfering ions in future adsorption experiments.