Biochar pyrolytically produced from municipal solid wastes for aqueous As(V) removal: Adsorption property and its improvement with KOH activation

• Excellent adsorption performance of aqueous As(V) by MSW biochars.
• 2 M KOH activated MSW biochars were more favorable for As(V) adsorption.
• Second-order model and Langmuir equation for better description of adsorption.
• Porosity and functional group changes promoted As(V) adsorption on MSW biochars.

Biochar converted from waste products is being considered as an alternative adsorbent for removal of aqueous heavy metal(loid)s. In this work, experimental and modeling investigations were conducted to examine the effect of biochars pyrolytically produced from municipal solid wastes on removing aqueous As(V) before and after activated by 2 M KOH solution. Results showed that the highest adsorption capacity of pristine biochars was 24.49 mg/g. The pseudo-second-order model and Langmuir adsorption isotherm model can preferably describe the adsorption process. The activated biochar showed enhanced As(V) adsorption ability with an adsorption capacity of 30.98 mg/g, which was more than 1.3 times of pristine biochars, and 2–10 times of modified biochars reported by other literatures. Increase of surface area and changes of porous texture, especially the functional groups on the surface of activated biochars are the major contributors to its more efficient adsorption of As(V).