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There has been a ton of debate on developing goals and the conflicts regarding environmental preservation. In the wastewater treatment industry, biochar seems to appear as a low-cost and environmentally friendly alternative because of its high porosity and adsorbent capacity. This study used the Scopus database to map articles on the topic through a systematic methodology and screening. The results demonstrate the approach researchers are giving to biochar adsorbing characteristics. It was observed that research about biochar applied to wastewater is recent and shortage. China and India were the countries that most published about it. Sewage sludge was the most common biomass used for biochar production, and pyrolysis temperature remained mainly at 300° C to 700 °C. Also, the removal of heavy metals was the greater purpose of the studies. Finally, this mapping described biochar formation and its use as an adsorbent for wastewater treatment purposes, providing important data for directing future studies. [ABSTRACT FROM AUTHOR]

Flue gas desulfurization-derived wastewater sludge (FGD-WWS) has been produced increasingly in China and India etc., and its content of heavy metals (HMs) including Cd, Cr, Cu, Hg, Ni and Zn seriously exceeds the limits allowed. Developing the suitable disposal of FGD-WWS is therefore significantly important and necessary. The novel process of electrokinetic treatment combined with chemical pretreatment of HMs in FGD-WWS were proposed here to improve the removal efficiency. Results indicate that the effects of different pretreatment agents (citric acid (CA), ammonia, tetrasodium of N, N-bis (carboxymethyl) glutamic acid (GLDA), and rhamnolipid) on the ET of HMs were different. To investigate the mechanism of combined process, the transformation potential (TP), exchange potential (EP) and removal potential (RP) were calculated. Correlation analysis shows the correlation between TP and RP was higher than that between EP and RP, indicating that the removal efficiency is mainly affected by the fraction transformation of HMs. Electric field, pH and pretreatment agents are main factors causing fraction transformation and affecting TP. Focusing on fraction transformation is an efficient way to improve further the removal efficiency. The work is promisingly valuable for developing the technology of treating FGD-WWS. [Display omitted] • The electrokinetic treatment and chemical pretreatment improve removal efficiency. • Chemical pretreatment with different agent has totally different effect. • The removal efficiency is mainly affected by the fraction transformation. • Adding different pretreating agents facilitate the fraction transformation. [ABSTRACT FROM AUTHOR]