Production of hydrochar from corn silk by hydrothermal carbonization technique and its modification for more effective removal of Cr(VI)

Abstract

The objective of this project was to develop a new bioproduct that will utilize agricultural waste and modify the product to increase its present adsorption capacity. After the hydrothermal carbonization of corn silk, a novel hydrochar was generated and treated using sulfuric acid to boost its adsorption capacity. FT‐IR, SEM–EDX, TGA, and BET surface analysis studies were used to analyze the structure of the produced biosorbents. According to the EDX analysis results, there are C, H, and N elements in the hydrochar structure, and the treated hydrochar contains S in addition to these elements. While the presence of several functional groups was indicated by FT‐IR data, post‐adsorption EDX analysis proved that Cr ions were adhering to hydrochar. The proper parameters for the adsorption processes for both biosorbents were established. By analyzing the outcomes of kinetics tests at various concentrations and isotherm experiments, the adsorption procedure was identified. The pseudo‐second‐order kinetic model was shown to be consistent with the kinetic pathways of adsorptions. Although the results of the isotherm experiments also suited the Langmuir isotherm, the Freundlich isotherm had higher R2 values and was more consistent with the results. The outcomes demonstrated that sulfuric acid‐modified hydrochar offered greater Cr(VI) adsorption capacity. qm values defining the maximum adsorption capacities of HC and THC at a temperature of 333 K were estimated to be 263.16 and 294.12 mg g−1, in that order. Based on the qm values, the adsorption capabilities of HC and THC were compared with those of a few other adsorbents. THC (29.11 m2 g−1) had a 29% larger surface area than HC (22.57 m2 g−1), according to the surface area of BET test results.