Application Research of Biochar for the Remediation of Soil Heavy Metals Contamination: A Review

Abstract

Soil contamination by heavy metals threatens the quality of agricultural products and human health, so it is necessary to choose certain economic and effective remediation techniques to control the continuous deterioration of land quality. This paper is intended to present an overview on the application of biochar as an addition to the remediation of heavy-metal-contaminated soil, in terms of its preparation technologies and performance characteristics, remediation mechanisms and effects, and impacts on heavy metal bioavailability. Biochar is a carbon-neutral or carbon-negative product produced by the thermochemical transformation of plant- and animal-based biomass. Biochar shows numerous advantages in increasing soil pH value and organic carbon content, improving soil water-holding capacity, reducing the available fraction of heavy metals, increasing agricultural crop yield and inhibiting the uptake and accumulation of heavy metals. Different conditions, such as biomass type, pyrolysis temperature, heating rate and residence time are the pivotal factors governing the performance characteristics of biochar. Affected by the pH value and dissolved organic carbon and ash content of biochar, the interaction mechanisms between biochar and heavy metals mainly includes complexation, reduction, cation exchange, electrostatic attraction and precipitation. Finally, the potential risks of in-situ remediation strategy of biochar are expounded upon, which provides the directions for future research to ensure the safe production and sustainable utilization of biochar.

Removal Mechanisms of Slag against Potentially Toxic Elements in Soil and Plants for Sustainable Agriculture Development: A Critical Review

“…While at the plant level, the application of slag-based fertilizers causes an increase in the antioxidant defense system and causes a reduction in the translocation of PTEs to plant shoots. However, the mechanisms for PTE ion remediation by slag are similar to many other applied amendments in previous studies, such as lime [88], biochar [89][90][91][92], zeolite [93], chitosan [94], the indigenous strain Bacillus XZM [95], hydrogen sulfide [96], and sepiolite [97]. The basic PTE ion immobilization on the slag surface was attributed to the presence of silicate, ferrites, and calcium oxides on the surface [98].…”

Recent advances in the valorization of plant biomass

“…Bio-char has received more attention in recent years, and several reviews have summarized its production [ 101 , 154 – 157 ]. Bio-char presents porous structure, abundant functional groups, high surface area, which includes minerals and trace metals [ 158 ], so it shows a wide range of applications, including adsorption (chemical substances [ 159 , 160 ], dye [ 161 , 162 ], and heavy metals [ 17 , 163 , 164 ]), catalysis [ 165 – 168 ], soil repair [ 163 , 169 ], and use as building materials [ 170 ], electrochemical energy storage [ 171 – 173 ], etc. During the process of bio-oil or bio-char production, syngas containing hydrogen, carbon monoxide, methane, etc.…”

Biochar and Its Broad Impacts in Soil Quality and Fertility, Nutrient Leaching and Crop Productivity: A Review

“…Studies have shown that use of organic materials that have high pH, CEC, surface area, and porosity such as biochar can ameliorate contaminated soil due to their efficiency at adsorbing HMs from soils (Table 3), [20,115,134]. Field and greenhouse studies have shown that application of biochar increased plant growth and reduced the uptake of HMs [6,74,135,136].…”