Oil removal from wastewater with biomass-derived hydrochars laboratory insights.

This study investigates the use of hydrochars derived from sweet potato residue (Ipomoea batatas), Indian mallow (Abutilon theophrasti Medicus), and Nan bamboo (Phyllostachys edulis) for diesel adsorption in oily wastewater treatment. Hydrochars were prepared via hydrothermal carbonization, and their adsorption kinetics and thermodynamics were evaluated. The optimal adsorption conditions for sweet potato residue hydrochar (SPRH) were: 1.8 g·L dosage, 479 mg·L diesel concentration, pH 4-, and 120-min adsorption time, with a capacity of 165.52 mg·g. Kinetic studies revealed that adsorption followed a pseudo-second-order model, and the isotherm fitted the Langmuir model. For Indian mallow hydrochar (IMH), optimal conditions were: 1.4 g·L dosage, 398 mg·L diesel concentration, pH 3.18, and 100 min, achieving 157.41 mg·g capacity. IMH adsorption also followed the pseudo-second-order model, driven by chemical adsorption. Nan bamboo hydrochar (NBH) showed optimal conditions at 1.8 g·L dosage, 502 mg·L diesel concentration, pH 3.92, and 120 min, with a diesel adsorption capacity of 193.75 mg·g. Chemical modification of NBH with KMnO, HO, HPO, and HNO improved adsorption by 12.38-21.25%. After four adsorption-desorption cycles, modified NBH retained 63.24% of its initial capacity, indicating good stability and regeneration potential. These findings suggest that modified NBH offers a cost-effective, efficient solution for oily wastewater treatment.