Application of raw Vigna subterranean husks as novel sorbent for abstraction of petroleum from contaminated waters

Abstract

The potential of raw V. subterranean husks (RVSH) as a novel natural sorbent, and an environmentally friendly and low-cost product for the cleanup of petroleum from contaminated waters was investigated. Characterization of the sorbent was accomplished with scanning electron microscope (SEM), Fourier transform infrared (FTIR), Brunauer–Emmett–Teller (BET) surface area analysis and thermogravimetric analysis (TGA). Batch sorption approach was applied to assess the impact of sorbent dose, pH, initial concentration, temperature as well as time. Crude oil characterization disclosed light oil owing to the oAPI gravity of 36.5°. The Langmuir model offered a superlative fit to the experimental data with greater regression coefficient (R2) and lower chi-square (χ2) and sum of squares of the errors (SSE) contrary to Temkin, Freundlich, Scatchard models and also produced maximum monolayer sorption capacity of 3.79 g/g. The pseudo-second-order model was more appropriate for kinetic considerations than first-order, intraparticle diffusion and liquid film diffusion models, and equilibrium sorption time of 70 min was achieved. Thermodynamic considerations presented an endothermic, non-spontaneous and physicochemical sorption process and also an improvement in randomness of the petroleum-RVSH interface. Recovery was good as 60.58% of the sorbate was salvaged using n-hexane as stripping agent, and reusability of the sorbent was also achieved after each cycle of sorption–desorption analysis. Therefore, the sorbent is suitable in the management of oil-contaminated water bodies.