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[Display omitted] • ZnCl 2 -activated biochar from sludge successfully adsorbed total NAs in raw OSPW. • Pore filling, hydrogen bonding, and π − π interactions were the adsorption mechanisms. • Biochar had selectivity for NAs with hydrophobic and higher cyclicity characteristics. • Microtox® assay indicated 66% reduction in acute toxicity after biochar treatment. • 91% reduction of bioavailability of organics was observed in OSPW treated with sludge biochar. Large volumes of oil sands process water (OSPW) containing naphthenic acids (NAs) and other contaminants are generated by oil sands operations. For the first time, pristine and zinc chloride-activated biochars from sludge from a municipal wastewater treatment plant are studied in the adsorption of NAs in real OSPW. By using activated biochar instead of pristine biochar, the adsorption capacity (q t) for total NAs (classical and oxidized NAs) increased from 2.3 to 26.6 mg/g. The increase in q t for activated biochar was related to the improvement of surface area from 7.9 to 513 m2/g, the abundance of mesopores (89% of pore volume), and the oxygen-containing surface groups. Equilibrium was reached at 2 h of contact time. Considering the thousands of structures of NAs in the OSPW, the activated biochar presented higher affinity for NAs with higher carbon and double bond equivalency numbers, therefore, NAs with more hydrophobic and higher cyclicity characteristics. Pore-filling, hydrogen bonding, and π-π interactions are the adsorption mechanisms. Thermal regeneration of spent activated biochar was studied, and in the fifth cycle of regeneration, the regenerated biochar had q t of 7.1 mg/g, which was 5 times higher than the adsorption capacity of fresh pristine biochar. Adsorption treatment of OSPW using activated biochar decreased the following parameters: metals Mg (7%), Ca (21%), Sr (27%), and Ba (60%), organic matter by means of DOC (63%) and COD (66%), acute toxicity towards V. fischeri (66%) and bioavailability of organics (91%). These findings promote circular economy as it presents an efficient adsorbent for NAs in OSPW developed from sludge, reducing the environmental impact associated with sludge disposal and allowing the efficient reclamation and reuse of OSPW. [ABSTRACT FROM AUTHOR]

Large amounts of process water with considerable concentrations of recalcitrant organic contaminants, such as polycyclic aromatic hydrocarbon (PAHs), phenolic compounds (PCs), and benzene, toluene, ethylbenzene, and xylene (BTEX), are generated by several segments of oil and gas industries. These segments include refineries, hydraulic fracturing (HF), and produced waters from the extraction of shale gas (SGPW), coalbed methane (CBMPW) and oil sands (OSPW). In fact, the concentration of PCs and PAHs in process water from refinery can reach 855 and 742 mg L−1, respectively. SGPW can contain BTEX at concentrations as high as 778 mg L−1. Adsorption can effectively target those organic compounds for the remediation of the process water by applying carbon-based adsorbents generated from organic feedstocks. Such organic feedstocks usually come from organic waste materials that would otherwise be conventionally disposed of. The objective of this review paper is to cover the scientific progress in the studies of carbon-based adsorbents from organic feedstocks that were successfully applied for the removal of organic contaminants PAHs, PCs, and BTEX. The contributions of this review paper include the important aspects of (i) production and characterization of carbon-based adsorbents to enhance the efficiency of organic contaminant adsorption, (ii) adsorption properties and mechanisms associated with the engineered adsorbent and expected for certain pollutants, and (iii) research gaps in the field, which could be a guidance for future studies. In terms of production and characterization of materials, standalone pyrolysis or hybrid procedures (pyrolysis associated with chemical activation methods) are the most applied techniques, yielding high surface area and other surface properties that are crucial to the adsorption of organic contaminants. The adsorption of organic compounds on carbonaceous materials performed well at wide range of pH and temperatures and this is desirable considering the pH of process waters. The mechanisms are frequently pore filling, hydrogen bonding, π−π, hydrophobic and electrostatic interactions, and same precursor material can present more than one adsorption mechanism, which can be beneficial to target more than one organic contaminant. Research gaps include the evaluation of engineered adsorbents in terms of competitive adsorption, application of adsorbents in oil and gas industry process water, adsorbent regeneration and reuse studies, and pilot or full-scale applications. [Display omitted] • Organic contaminants are a concern in process water (PW) from oil and gas operations. • Scientific progress in carbon-based adsorbents for organic contaminants is covered. • Adsorption efficiency is enhanced with production conditions of carbon-based material. • Future study must focus on real PW to assess adsorption efficiency and competitivity • Research gaps include regeneration/reuse and environmental impacts of spent adsorbent. [ABSTRACT FROM AUTHOR]

Abstract: Water is integral to both operational and environmental aspects of the oil sands industry. A water treatment option based on the use of petroleum coke (PC), a by-product of bitumen upgrading, was examined as an opportunity to reduce site oil sands process-affected water (OSPW) inventories and net raw water demand. Changes in OSPW quality when treated with PC included increments in pH levels and concentrations of vanadium, molybdenum, and sulphate. Constituents that decreased in concentration after PC adsorption included total acid-extractable organics (TAO), bicarbonate, calcium, barium, magnesium, and strontium. Changes in naphthenic acids (NAs) speciation were observed after PC adsorption. A battery of bioassays was used to measure the OSPW toxicity. The results indicated that untreated OSPW was toxic towards Vibrio fischeri and rainbow trout. However, OSPW treated with PC at appropriate dosages was not acutely toxic towards these test organisms. Removal of TAO was found to be an adsorption process, fitting the Langmuir and Langmuir–Freundlich isotherm models. For TAO concentrations of 60mg/L, adsorption capacities ranged between 0.1 and 0.46mg/g. This study demonstrates that freshly produced PC from fluid cokers provides an effective treatment of OSPW in terms of key constituents'' removal and toxicity reduction. [Copyright &y& Elsevier]

Classical adsorbents such as activated carbon are inefficient to remove Cu(II)-EDTA in solution. Moreover, the heavy metals in the generated sludge can easily be dissolved back into solution. In this research, a novel strategy developed by coupling green rust adsorption and ferrite formation technology was proposed for Cu(II)-EDTA chelate removal. At the adsorption stage, green rust sulfate (GR ME (SO 4 2−)) showed a high adsorption efficiency of chelated copper, with a capacity of 126.41 mg g−1, compared to other classical adsorbents. During the ferrite formation stage, GR ME (SO 4 2−)-based precipitate with high moisture content and slow settling rate could be transformed into ferrite-based precipitate with low moisture content and rapid settling rate. The volume and moisture content of ferrite were 2.20 and 1.45 times lower than those of GR ME (SO 4 2−) and the sedimentation velocity of ferrite was also 1.23 times higher than that of GR ME (SO 4 2−), which strongly demonstrated the necessity of the ferrite formation process. Toxicity characteristic leaching procedure (TCLP) test results showed that the metallic copper of GR ME (SO 4 2−) sludge could be more easily dissolved back into solution than that of ferrite precipitate under weak-acid conditions, indicating the stability of ferrite. In addition, after the ferrite process, the generated sludge exhibited soft magnetism and could be quickly separated within few seconds using an external magnetic field. All these results showed that the combined green rust adsorption with ferrite formation method was an efficient, recyclable and eco-friendly method for the treatment of wastewater containing Cu(II)-EDTA. Image 1 • The Fe/C microelectrolysis effluent could be applied for green rust preparation. • Green rust was an efficient adsorbent for Cu(II)-EDTA removal. • Operational variables were optimized by response surface methodology. • The ferrite process improved the sludge stability. • The final sludge could be recycled as magnetic material. [ABSTRACT FROM AUTHOR]

The oil production generates large volumes of oil sands process-affected water (OSPW), referring to the water that has been in contact with oil sands or released from tailings deposits. There are concerns about the environmental impacts of the release of OSPW because of its toxicity. Zero valent iron alone (ZVI) and in combination with petroleum coke (CZVI) were investigated as environmentally friendly treatment processes for the removal of naphthenic acids (NAs), acid-extractable fraction (AEF), fluorophore organic compounds, and trace metals from OSPW. While the application of 25 g/L ZVI to OSPW resulted in 58.4% removal of NAs in the presence of oxygen, the addition of 25 g petroleum coke (PC) as an electron conductor enhanced the NAs removal up to 90.9%. The increase in ZVI concentration enhanced the removals of NAs, AEF, and fluorophore compounds from OSPW. It was suggested that the electrons generated from the oxidation of ZVI were transferred to oxygen, resulting in the production of hydroxyl radicals and oxidation of NAs. When OSPW was de-oxygenated, the NAs removal decreased to 17.5% and 65.4% during treatment with ZVI and CZVI, respectively. The removal of metals in ZVI samples was similar to that obtained during CZVI treatment. Although an increase in ZVI concentration did not enhance the removal of metals, their concentrations effectively decreased at all ZVI loadings. The Microtox® bioassay with Vibrio fischeri showed a decrease in the toxicity of ZVI- and CZVI-treated OSPW. The results obtained in this study showed that the application of ZVI in combination with PC is a promising technology for OSPW treatment. [Copyright &y& Elsevier]