Application of biochar-based photocatalysts for adsorption-(photo)degradation/reduction of environmental contaminants: mechanism, challenges and perspective

Abstract

The fast increase of population results in the quick development of industry and agriculture. Large amounts of contaminants such as metal ions and organic contaminants are released into the natural environment, posing a risk to human health and causing environment ecosystem problems. The efficient elimination of contaminants from aqueous solutions, photocatalytic degradation of organic pollutants or the in-situ solidification/immobilization of heavy metal ions in solid phases are the most suitable strategies to decontaminate the pollution. Biochar and biochar-based composites have attracted multidisciplinary interests especially in environmental pollution management because of their porous structures, large amounts of functional groups, high adsorption capacities and photocatalysis performance. In this review, the application of biochar and biochar-based composites as adsorbents and/or catalysts for the adsorption of different contaminants, adsorption-photodegradation of organic pollutants, and adsorption-(photo)reduction of metal ions are summarized, and the mechanism was discussed from advanced spectroscopy analysis and DFT calculation in detail. The doping of metal or metal oxides is the main strategy to narrow the band gap, to increase the generation and separation of photogenerated e−-h+ pairs, to produce more superoxide radicals (·O2−) and hydroxyl radicals (·OH), to enhance the visible light absorption and to increase photocatalysis performance, which dominate the photocatalytic degradation of organic pollutants and (photo)reduction of high valent metals to low valent metals. The biochar-based composites are environmentally friendly materials, which are promising candidates in environmental pollution cleanup. The challenge and perspective for biochar-based catalysts are provided in the end. Graphical Abstract

Acrylonitrile Adducts: An Efficient Adsorbent Media for Removal of Iron from Water

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Engineered inverse opal structured semiconductors for solar light-driven environmental catalysis

“…25 The photocatalytic reduction of Cr( vi ) to Cr( iii ) with low toxicity is an environmentally-friendly method to remove Cr( vi ). 212,213 Lv et al 132 used IO-TiO 2 for the photocatalytic reduction of Cr( vi ) by electrons photoinduced under UV light irradiation to reduce Cr( vi ) to Cr( iii ). To improve the photocatalytic reduction of Cr( vi ) under visible light, cobalt phosphate nanoparticles were photodeposited on the surface of IO-TiO 2 (Co-Pi/i.o.…”

Accordion-like Multilayered Two-Dimensional Ti3C2Tx MXenes for Catalytic Elimination of Organic Dyes from Wastewater via the Fenton Reaction

“…Therefore, the removal of dyes from wastewater before discharging it into the environment is an essential step. Various methods such as adsorption, , precipitation, membrane filtration, and photocatalytic oxidation ,, for wastewater treatment have been reported by many scientists over the years. However, each method has its limitations, including high operation costs, higher energy consumption, and excess sludge production .…”