Bio/hydrochar Sorbents for Environmental Remediation

摘要

A rising global population and aspirational higher living standards has driven a step change in resource utilization and concomitant anthropogenic pollution across the biosphere.Low-cost and scalable technologies for environmental remediation are therefore urgently sought,with an emphasis on trash-to-treasure strategies that exploit abundant but underutilized waste by-products of existing sectors.Biochars are carbon-rich,porous solids produced by biomass pyrolysis under anaerobic or oxygen-scarce conditions at high temperature(350–700°C),while hydrochars are produced by hydrothermal biomass carbonization at lower temperature(130–250°C)and high autogenous pressures(0.3–4.0 MPa).Bio/hydrochars possess unique physicochemical properties,notably high surface areas(100–1500 m2 g-1)and porosity(0.25–2.5 cm^(3)g^(-1))and rich surface chemistry featuring carboxylic,phenolic,hydroxyl,and carbonyl functions,amenable to chemical,physical,or biochemical modification,rendering them ideal sorbents for pollutants such as heavy metals(e.g.As and Cr),and toxic organic(e.g.,dyes and xenobiotics)and inorganic(e.g.,SO_(2))molecules.Bio/hydrochars are attractive for environmental remediation of pollutant mixtures by surface complexation,redox chemistry,electrostatic interactions/ion exchange,or coprecipitation.This review discusses recent opportunities and challenges in creating bio/hydrochar sorbents and their nanocomposites through grafting,doping,and chemical/physical activation,for the depollution of aquatic and atmospheric environments.