Chapter 16 - Mechanism of metal sorption by biochar

Abstract

Biochar is a charcoal produced by the pyrolysis of biomass in the absence of oxygen. It absorbs the heavy metal pollutants tightly and removes them from the soil. In recent years, biochar has gained more attention due to its multifunctionality, which includes sequestration of carbon, soil fertility enhancement, environmental remediation, and bioenergy production. It is a low-cost absorbent that can also be used for wastewater treatment. Various studies have been done on the effectiveness of biochar for the removal of heavy metals by aqueous solution. This chapter examines and summarizes biochar production and its ability to remove heavy metals, feedstock material, mechanism of heavy metal, introduces the relevant adsorption parameters, its mechanism on organic pollutants, its application and finally analyze its benefits and development prospects. Besides increasing soil fertility and therefore agricultural productivity, biochar reduces greenhouse emissions. From past studies, biochar-based sorbents have heavy metal adsorption capacities in mg/g of 1217 (Ag), 560 (Pb), 288 (Cu), 216 (Cd), 204 (As), 130 (Cr), 58 (Ni), 48 (Hg), etc., under optimal conditions. Though the kinetic model of nature and isotherms depend on the material and process conditions, pseudokinetic models (first and second order) along with Langmuir and Fruendlich isotherms are the most widely reported. Spent biochar could be used in the construction (cement and bricks) and electronic (supercapacitor) industries in addition to phytoremediation.