Advancement of biochar-aided with iron chloride for contaminants removal from wastewater and biogas production: A review

The use of fossil fuels, emission of greenhouse gases (GHG) into the atmosphere, and waste pose a problem to the en-vironment and public health that urgently needs to be dealt with. Among numerous chemical activating agents that can be added to anaerobic digestion (AD) to enhance nutrient removal and increase the quality and quantity of biomethane, iron chloride (FeCl3) is the one that has the lowest cost and is the most environmentally friendly. This state-of-the-art review aims to revise the influence of FeCl3 on the Brunauer-Emmett-Teller (BET) surface area of bio-char and its ability to increase methane (CH4) yield and remove contaminants from biogas and wastewater. The nov-elty of the study is that FeCl3, an activating agent, can increase the BET surface area of biochar, and its efficacy increases when combined with zinc chloride or phosphoric acid. Regarding the removal of contaminants from waste-water and biogas, FeCl3 has proven to be an effective coagulant, reducing the chemical oxygen demand (COD) of wastewater and hydrogen sulfide in biogas. The performance of FeCl3 depends on the dosage, pH, and feedstock used. Therefore, FeCl3 can increase the BET surface area of biochar and CH4 yield and remove contaminants from wastewater and biogas. More research is needed to investigate the ability of FeCl3 to remove water vapor and carbon dioxide during biogas production while accounting for a set of other parameters, including FeCl3 size.