A mini-review on engineered biochars as emerging adsorbents in heavy metal removal

Abstract

Environmental remediation using green adsorbents has been the primary focus of researchers worldwide to promote a sustainable and safe environment. Engineered biochars (E-BCs) from different biomass feedstocks have become highly successful adsorbents to remove heavy metals due to their conducive properties like large surface areas and enhanced functionalities, thereby giving higher removal efficiencies and cyclic stabilities. In this mini-review, an analysis with respect to synthesis, biosorption mechanism, modification methods, and performance comparison with respect to adsorption capacity (AC) of engineering biochars’s are discussed. The coconut shell (AC: 450.50 mg/g), pennisetum sp.straw-a weed species (AC: 763.12 mg/g), Douglas fir bark wood (AC: 127.20 mg/g), corncob (9.62 mg/g) are observed to be the best biosorbent for the heavy metal removal of Pb(II), Cd(II), Cr(VI), and As(V) from aqueous solution. The acid treatment, alkali treatment, salt treatment, oxides treatment, ball milling, steam activation, alumina nanoparticles, magnetic activation, chitosan modification, and nanoscale zero valent iron (nZVI) are the common modification methods to develop E-BC. The future challenges and prospects are also discussed.