الفهرس | Only 14 pages are availabe for public view |
Abstract In this study, more attentions have been directed to utilize solid/liquid waste byproducts as zero-cost starting precursors for synthesize effective sorbent materials for petroleum wastewater treatment. IN this regard, both pulping black liquor and palm-date pits industrial wastes were treated via chemical and thermal processes to generate three series of carbon-based materials: granule activated carbon (gAC), 3D cross-linked Kraft lignin biopolymer (KL), and hybrid biocomposites (gAC/KLx, x= 33, 50 and 67%). The prepared materials were fully characterized to understand their crystalline nature, surface morphologies, functionalities, surface area, porosity, surface charges, and thermal and aqueous stabilities. The potential applicability of these materials towards the removal of mono-aromatics pollutants mixture (such as benzene, toluene, and xylene: termed as BTX) was investigated in batch adsorption process. The effect of adsorption parameters, including pH (3 -9), ionic strength (0 -100 g/L NaCl), adsorbent dose (5 -25 g/L), BTX concentrations (750 – 2250 mg/L), contact time (10 min – 24 h), and temperature (293 – 323 K), on the adsorption performance were investigated and optimized. Moreover, the adsorption modeling via kinetic, isotherm, and thermodynamic analysis were studied to understanding the mechanism of BTX sorption onto the prepared gAC, KL, and gAC/KLx hybrids sorbents during oilfield wastewater treatment. The studied adsorption processes were evaluated using high performance liquid chromatography (HPLC). Results indicated that the adsorption equilibrium of the BTX pollutants onto the prepared adsorbent was achieved after 12 contacted time. It was found that the prepared adsorbents have higher capability to achieve the highest BTX capacity at broad ranges of ionic strength (0-100 g/L NaCl), pH (3 - 9), temperature (293 -323K). The adsorption performance of BTX onto gAC and gAC/KL was enhanced by increasing ionic strength to 100 g/L due to salting out effect, which increase BTX hydrophobicity and reduce ionic surface charge to promote mass diffusion mechanism. However, it should be noted that the KL performance at higher ionic strength decreased due to the instability of biopolymer. Both gAC and hybrid gAC/KL at 50% blend ratio exhibited the highest effectiveness for BTX removal (~100% of 750 mg/L BTX) over 5 reuse cycles, with higher selectivity in the order of xylene > toluene> benzene. Comparatively, KL biopolymer exhibited poor adsorption performance (52.6±3.4% removal) and low stability over 5 reuse cycles with good selectivity for benzene over toluene and xylene. Non-linear modeling of adsorption kinetic (nine models) and isotherm (five models) reflected the best fit of experimental adsorption data to mixed-order kinetic (MOE) and Langmuir-Freundlich (L-FM) isotherm models. Such models fit to experimental adsorption data indicated the existence of complex phenomena during adsorption of BTX molecules onto the prepared adsorbent surfaces. Based on kinetic and isotherm constants, the adsorption mechanism suggested to best described by physico-sorption (activation energy E ≈ 0.12 – 1.38 KJ/mol) via the hydrophobic interaction and diffusion mechanisms. In respect to adsorption affinities, the sorption of BTX molecules onto gAC and gAC/KL0.5 followed the descending sequence of X (0.96 – 0.164 L/mg) > T (0.041 - 0.078 L/mg) > B (0.022 -0.009 L/mg). The maximum theoretical BTX capacity using the best fitted Langmuir-Freundlich model (L-FM) for gAC/KL0.5 was found to be higher than obtained by gAC (363.9 and 360.1 mg/g, respectively), 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). Particularly, thermodynamic analysis indicated favorable adsorption process of BTX onto gAC and gAC/KL0.5 than pure KL sorbent. The sorption process is physisorption (ΔH value < 80 kJ/mol), spontaneous, and endothermic in nature when using gAC and gAC/KL0.5 compared to non-spontaneity in nature onto KL biopolymer. Adsorption of BTX onto all the prepared adsorbents is mainly dependent on the nature of adsorbent surface, adsorbate type, and BTX concentration. For applied study, batch adsorption process for real-petroleum wastewater sample collected from one of the oil & gas company in Egypt was investigated. the application results verified the superior performance of gAC and gAC/KL0.5 adsorbents for complete removal of BTX and ethylbenzene pollutants (> 98.5±0.76%)along with other polar organics such as methanol (by ≈ 53.4 – 42.0%), mono-ethylene glycol (MEG = 64.3 – 47.8%), and diethylene glycol (DEG= 70.3 – 43.5%). Economic cost analysis reflected that the production cost of gAC/KL0.5 adsorbent (2.81±0.55 US $/kg) is low than of gAC (∼3.73±0.32 US $/kg), and both are lower in cost than commercially activated carbon in market place. At this end, it is suggested that gAC/KL0.5 could be used as potential eco-friendly, low-cost, and effective sorbent for treatment of petroleum wastewater before disposal for save our natural ecosystem up to five reuse cycles. Keywords Waste management, Activated carbon, Kraft lignin-based biocomposite, BTX adsorption, Non-linear kinetic and isotherm modeling, Petroleum wastewater treatment. |