The utilization of activated Carbon/Lignin biocomposite as recyclable sorbent for in-situ removal of high-concentration BTX from petroleum wastewater

Abstract

Among varies petroleum pollutants of interest, BTX (i.e., benzene, toluene, and xylene of ortho, meta and para-positions) mono-aromatics has found to be the most environmental problem [1]. Environmental legalization policies are listed BTX as contaminants of emerging concerns (CECs) because of their potential toxic and/or carcinogenic properties for human health or animals and drinking water contamination, even in trace levels [2]. In this work, a facile one-pot co-precipitation process was developed to construct granule activated carbon (gAC)/Kraft lignin (KL) biocomposite (gAC/KLx) as a new eco-friendly sorbent from recycling industrial wastes of both palm-date pits and pulping black liquor. The synthesized gAC/KLx biocomposite with defined characteristics using ATR-FTIR, XRD, SEM, BET, TGA, DLS and Zeta potential analyses was utilized as an effective sorbent of environmentally toxic BTX compounds (benzene, toluene and xylene) from petroleum wastewater effluents. Sorption behavior of BTX over gAC/KLx biocomposites with different ratios of Kraft lignin (x = 33, 50 and 67%) in batch experiments were evaluated using high performance liquid chromatography (HPLC). Interestingly, the gAC/KL showed the highest sorption capacity of BTX at lignin blended ratio of 50%, even from broad ranges of water salinity (up to 100,000 mg/L) and pH values (pH 4 - 9). The sorption behavior of BTX compounds were found to fit better to a type two pseudo-second kinetic (adsorption kinetic rate of BTX at 0.104 g.mg-1.min-1) and Langmuir isotherm models, as confirmed by the higher coefficient of R2 > 0.98. The sorption affinities of the gAC/KL0.5 biocomposite with respect to 250 mg/L BTX can be ordered in the sequence Xylene > Toluene ≥ benzene with highest monolayer capacities reached to 170.5, 160.5 and 159.7 mg/g, respectively after 6 h. The adsorption mechanism was found to follows the diffusion and hydrophobic sorption mechanisms. Particularly, the possibilities of BTX elution for gAC/KL0.5 reuse were evaluated up to five cycles without high significant loss in sorption efficiencies during multiple wastewater treatment. As such, on the basis of batch BTX sorption studies, the gAC/KL0.5 is expected to be a promising low cost and high performance new sorbent to be reutilize for real wastewater treatment process and petroleum hazardous decontamination with higher thermal stability (up to 350 °C) and aqueous stability (10% - 21% efficiency loss).