Synthesis of recyclable carbon/lignin biocomposite sorbent for in-situ uptake of BTX contaminants from wastewater

Abstract

In this work, both palm-date pits and pulping black liquor industrial wastes were recycled as low-cost starting materials for the production of three series of granule activated carbon (gAC)/Kraft lignin (KL) (gAC/KLx, x = 33, 50 and 67%) biocomposites using a one-pot solid-state method. The gAC/KLx biocomposites with defined characteristics were examined towards batch adsorption of BTX (Benzene, Toluene, and Xylene) in multi-solute salty wastewaters. Optimization of adsorption performances under different experimental conditions were carried out using high performance liquid chromatography (HPLC). Adsorption modeling versus contact time (0–12 h) and BTX concentrations (150–2250 mg/L) were examined using non-linear forms of nine kinetic and five isotherm equations to best understand gAC/KL0.5 suitability for BTX sorption/recovery processing. Accordingly, the gAC/KLx at KL blended ratio of 50% was found to be the topmost to achieve the highest BTX capacity even at broad ranges of water salinity (0–100 g/L) and pH (3–9) values. The adsorption mechanism found to best described by physico-sorption (E ≈ 0.12–1.38 kJ/mol) via the hydrophobic interaction and diffusion mechanisms. In respect to gAC/KL0.5 affinities, the sorption capacity followed the descending sequence of X ≥ T > B. Particularly, the maximum theoretical BTX capacity using the best fitted Langmuir-Freundlich model (L-FM) for gAC/KL0.5 was found to be slightly higher than obtained by gAC (363.9 and 360.1 mg/g, respectively), along with higher initial sorption (h) rate (≈742.47 mg/g.h) than of gAC (≈559.85 mg/g.h) and KL (≈22.22 mg/g.h). Batch BTX sorption/recovery processes and estimated cost suggested the effective utilization of gAC/KL0.5 as a promising in-expensive sorbent (0.31 ± 0.05 US$/kg) for commercial decontamination of petroleum hazardous (BTX) pollutants from wastewaters up to five reuse cycles.