Removal of Metals and Dyes in Water Using Low-Cost Agro-Industrial Waste Materials

Abstract

The pollution of water bodies due to the discharge of effluents without treatment is a global problem. Therefore, different technologies have been implemented for the removal of contaminants from wastewater before the final disposition. Among them, adsorption processes using residual biomasses are becoming very popular due to the low cost and high availability of adsorbents. Thus, in the present work, the synthesis of modified biochar from agro-industrial residues derived from the wheat-processing industry, as a valorization alternative of these residues, for its use in the removal of Cr (VI) and methylene blue (MB) has been analyzed. The biochar was prepared using a ramp function of 5 °C/min until 250 °C for 30 min. The adsorption tests were developed in a batch system, using 30 mg of adsorbent in 10 mL of solution. From SEM analysis, the formation of tubular cavities and porous structure was seen, caused by the basic hydrolysis with KOH. From adsorption tests, an adsorption capacity of 12.98 mg/g and 97.38% of efficiency for MB at pH 10 was noted, while for Cr (VI), it was 11.35 mg/g and 85.15% at pH 2. Freundlich’s model adjusted the adsorption equilibrium data with R2 > 0.9. The maximum adsorption capacities in the monolayer were 186,375 mg/g and 90.723 mg/g for Cr (VI) and MB, according to Langmuir’s model. From a kinetic study, it can be said that the process occurs by chemisorption through electrostatic interaction and ionic interchange between adsorbate and adsorbent.