In recent years, numerous investigations have explored the use of biochar for the removal of organic and inorganic pollutants in single component systems. Biochar is a carbonaceous material produced from waste biomass, mainly by thermochemical conversion methods. This material was used as a biosorbent in various removal processes of pollutants, and its efficiency was strongly influenced by the characteristics of the biomass feedstock. This review integrates the recent works of literature to understand the biosorption behaviour of dyes onto biochar-based biosorbents. The factors influencing the biosorption process and the mechanisms describing the biosorption behaviours of the biochar have been broadly reviewed. Furthermore, the biosorption models can be used to comprehend the competence of the biochar as biosorbent for dye removal techniques. Graphical Abstract

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Optimization of process conditions for the removal of Remazol Black B was investigated using response surface methodology (Box–Behnken design). The biodecolorization of dye was studied using biochar produced from waste biomass of Caulerpa scalpelliformis (marine seaweeds). The reactions were optimized by varying sorbent dosage, solution pH, temperature, and initial dye concentration. The results indicated that dye removal efficiency of 80.30% was attained at an operating condition of 4 g/L (sorbent dosage), 2.0 (solution pH), 35°C (temperature), and 0.25 mmol/L (initial dye concentration). The regression coefficient of the developed model was calculated to be 97% which shows good fit of the model.

Organic pollutants, such as dyes released during industrial operations are one of the major reasons for the degradation of water quality. However, treatment technologies to remediate these high volumes of wastewaters are often not sufficient. Hence, the excess dye wastewater generated is usually discharged without prior treatment. The use of adsorbents such as activated carbon is widely employed to separate dye molecules from wastewater. Biochar is a popular recent alternative for the treatment of dye‐bearing effluents to selectively isolate dye molecules. Biochar is normally manufactured in the oxygen free environment by thermal degradation of organic materials. On the other hand, dyes are extensively employed in many textile industries because of their desirable properties including attractive colour, water‐fast and easy application methods. Nevertheless, during the dyeing process of cellulose fibres around half of the applied dyes may enter the wash water, and these let outs are highly resistant to traditional wastewater treatment methods. Henceforth, new techniques need to be applied for successful remediation of dye wastewaters. In this perspective, an endeavor has been made in this work to explore the possibility and practicability of biochar as sorbent material for dyes.

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