Abstract:
Heavy metals in the environment pose significant ecological and human health
concerns worldwide. Nano Zero-valent iron (nZVI) is a promising heavy metal
removal agent due to its non-toxicity and low standard reduction potential. Avoiding
agglomeration, passivation, and long-term stability requires a carrier. The porousness
and heavy metal binding properties of biochar (BC) make it an effective carrier. This
study presents a comparative evaluation of the remediation of Pb2+, Cd2+ and Ni2+ by
two nZVI-biochar nanocomposites produced via asynchronous (BC-nZVI) and
synchronous (BM-nZVI) routes of pyrolysis and carbothermal reduction. A
comprehensive evaluation of the effects of pH, contact time, and isotherm pattern
studies were carried out with BC serving as the control. The alkalinity of the medium
was contributive in the enhanced remediation. The optimal contact times were 50
minutes and 90 minutes for Cd2+ and Ni2+ respectively. For Pb2+, all materials
exhibited fast kinetics of adsorption. For Pb2+ and Ni2+, Langmuir model was best
fitted while the Cd2+ sorption was best described by Redlich-Peterson isotherm
model. BM-nZVI showed the highest Langmuir capacities of 36.403, 15.388 and
4.553 mg g-1
for Pb2+, Cd2+ and Ni2+ respectively. Decreased sorption of BC-nZVI
might be due to pore blockage. The present work demonstrates the efficiency of BM-nZVI for heavy metal remediation
