Unravelling the Environmental Application of Biochar as Low-Cost Biosorbent: A Review

Abstract

In this age, a key target for enhancing the competitiveness of the chemical, environmental and biotechnology industries is to manufacture high-value products more efficiently and especially with significantly reduced environmental impact. Under this premise, the conversion of biomass waste to a high-value added product, biochar, is an interesting approach under the circular economy principles. Thus, the improvements in the biochar production and its new and innovative uses are hot points of interest, which are the focus of vast efforts of the scientific community. Biochar has been recognized as a material of great potential, and its use as an adsorbent is becoming a reliable strategy for the removal of pollutants of different streams, according to its high adsorption capacity and potential to eliminate recalcitrant compounds. In this review, a succinct overview of current actions developed to improve the adsorption capability of biochar, mainly of heavy metal and organic pollutants (dyes, pharmaceuticals and personal care products), is summarized and discussed, and the principal adsorption mechanisms are described. The feedstock and the production procedure are revealed as key factors that provide the appropriate physicochemical characteristics for the good performance of biochar as an adsorbent. In addition, the modification of the biochar by the different described approaches proved their feasibility and became a good strategy for the design of selective adsorbents. In the last part of this review, the novel prospects in the regeneration of the biochar are presented in order to achieve a clean technology for alleviating the water pollution challenge.

Valorization of Rice Husk for the Production of Porous Biochar Materials

“…Pyrolysis, one of the commonly used thermochemical conversion processes, involves decomposition of biomass in the absence of air or oxygen at an elevated temperature [3]. The resulting biochar can be further used as solid fuel, carbon material, soil amendment, environmental adsorbent (biosorbent), functional catalyst or feedstock for chemicals, depending on its final applications [4][5][6][7][8][9].…”

From Circular Economy to Circular Ecology: A Review on the Solution of Environmental Problems through Circular Waste Management Approaches

“…The publications summarized in Tables 1-4 present different methods to solve environmental problems through circular approaches and combining heterogeneous processes, i.e., by applying CE L principles. Among the papers proposing new circular approaches for WM, the majority of them propose solutions to generate valuable products (e.g., adsorption materials, cellulose, chemicals, biofuels, fertilizers and soil improvers from agro-forestry, and zootechnical and food waste) [97,99,[102][103][104][105][106]110,111,113,[117][118][119][120][121]124,131,133,135,141], recover precious nutrients [128,134,136,137], exploiting sustainable sources of energy [45,100,101,109,110,114,115,123,125], and eliminate residual waste [112,126,129,132,[138][139][140].…”

“…Another well-known application of the CE L approach is the production of soil improvers from bio-waste, which is advantageous in terms of GHG emissions [95] and nitrogen contribution to soil with respect to commercial fertilizers [96]. Another interesting example of CE L consists in the production of biochar from organic waste and its potential use in several contexts [97].…”

Cadmium and lead adsorption and desorption by coffee waste-derived biochars

“…Among alternative techniques, heavy metal sorption by different sorbents has proven to be an effective and low-cost approach (Tomczyk et al 2019). Thus, using biochars as biosorbents has been widely reported in the scientific literature (Fdez-Sanromán et al 2020;Jiang et al 2016;Zhang et al 2018). Sorption of heavy metals by biochars occurs due to their high aromaticity and surface area, functional groups, and alkalinity.…”