Degradation Of Recalcitrant Organic Compounds Research Articles

Recent advances on the treatment of oilfield-produced water by advanced oxidation processes: A review

Abstract Despite the advancements in alternative fuels and energy sources, there continues to be a significant global dependence on oil production and extraction. A substantial volume of oilfield-produced water (OPW) is generated during the production and extraction processes of oil fields. Recurrent OPW treatments encountered significant challenges in addressing this particular type of wastewater. Advanced oxidation processes (AOPs) are regarded as a promising alternative approach for the degradation of recalcitrant organic compounds in the OPW. This review focuses on the characterization of OPW. The treatment of organic pollutants in wastewater using AOPs, such as ozonation, Fenton oxidation-based processes, heterogeneous photocatalysis, and persulfate oxidation, is comprehensively reviewed in terms of their efficiency for pollutant degradation. The primary challenges in this field and the future directions for development are proposed, with the aim of providing a valuable reference for achieving highly effective treatment of OPW.

Ozone-activated peroxymonosulfate (O3/PMS) process for the removal of model naphthenic acids compounds: Kinetics, reactivity, and contribution of oxidative species

Due to their recalcitrance, naphthenic acids (NAs) are one of the constituents of interest in oil sands process water (OSPW). In this study, peroxymonosulfate (PMS) activated by ozone was employed to degrade NA model compounds in buffer solutions. At an ozone/PMS ratio of 2:1, a removal of 85 % was observed for a model diamondoid NA compound (1-adamantanecarboxylic acid; ACA) after 45 s of reaction. Compared with ozone alone, the degradation of ACA was accelerated in the presence of ozone/PMS, with an overall pseudo-first order rate constant (kobs) increasing from 8.02 × 10−4 s−1 during ozone treatment to 6.74 × 10−2 s−1 in the ozone/PMS system. Although ozone/hydrogen peroxide (H2O2) showed high degradation for ACA, the ozone/PMS system showed a higher kobs of 5.44 × 10−2 s−1at a PMS dose of 0.042 mM, while at the same dose of H2O2, kobs was equal to 3.62 × 10−2 s−1 for ozone/H2O2. This result showed the synergetic effect of ozone and PMS on the degradation of ACA. Relative kinetics studies using mixtures of model NA compounds showed better performance for ozone/PMS to degrade aromatic NAs compared to ozone/H2O2. Hydroxyl radicals and sulfate radicals were found to be responsible for the removal of ACA, with limited effect of molecular ozone. The proposed degradation pathways for ACA included hydroxylation, carboxylation, and polymerization under ozone/PMS, while hydroxylation and carboxylation were the main degradation pathways under ozone/H2O2. The results of this study emphasize the potential of ozone/PMS process to treat OSPW by accelerating the degradation of recalcitrant organic compounds.

Intimately coupled photocatalysis and functional bacterial system enhance degradation of 1,2,3- and 1,3,5-trichlorobenzene.

Intimate coupling of photocatalysis and biodegradation (ICPB) is considered a promising approach for the degradation of recalcitrant organic compounds. In this work, using Trichoderma with benzene degradation ability coupled with activated sludge as a biological source and sugarcane bagasse cellulose composite as a carrier, the ICPB system showed excellent degradation and mineralization of trichlorobenzene under visible light induction. The biofilm inside the ICPB carrier can degrade and mineralize the photocatalytic products. ICPB increased the degradation efficiency of 1,2,3-TCB and 1,3,5-TCB by 12.43% and 4.67%, respectively, compared to photocatalysis alone. The biofilms inside the ICPB carriers can mineralize photocatalytic products, which increases the mineralization efficiency by 18.74%. According to the analysis of intermediates, the degradation of 1,2,3-TCB in this coupled system involved stepwise dechlorination and ring opening. The biofilm in ICPB carrier evolved to be enriched in Cutaneotrichosporon, Trichoderma, Apiotrichum, Zoogloea, Dechloromonas, Flavihumibacter and Cupriavidus, which are known for biodegradable aromatic hydrocarbon and halogenate. Novel microbial seeds supplemented with Trichoderma-based ICPB seem to provide a new potential strategy for effective degradation and mineralization of TCB.

Complete Genomes of the Anaerobic Degradation Specialists Aromatoleum petrolei ToN1T and Aromatoleum bremense PbN1T

The betaproteobacterial genus Aromatoleum comprises facultative denitrifiers specialized in the anaerobic degradation of recalcitrant organic compounds (aromatic and terpenoid). This study reports on the complete and manually annotated genomes of Ar. petrolei ToN1^T (5.41 Mbp) and Ar. bremense PbN1^T (4.38 Mbp), which cover the phylogenetic breadth of the genus Aromatoleum together with previously genome sequenced Ar. aromaticum EbN1^T [Rabus et al., Arch Microbiol. 2005 Jan;183(1):27–36]. The gene clusters for the anaerobic degradation of aromatic and terpenoid (strain ToN1^T only) compounds are scattered across the genomes of strains ToN1^T and PbN1^T. The richness in mobile genetic elements is shared with other Aromatoleum spp., substantiating that horizontal gene transfer should have been a major driver in shaping the genomes of this genus. The composite catabolic network of strains ToN1^T and PbN1^T comprises 88 proteins, the coding genes of which occupy 86.1 and 76.4 kbp (1.59 and 1.75%) of the respective genome. The strain-specific gene clusters for anaerobic degradation of ethyl-/propylbenzene (strain PbN1^T) and toluene/monoterpenes (strain ToN1^T) share high similarity with their counterparts in Ar. aromaticum strains EbN1^T and pCyN1, respectively. Glucose is degraded via the ED-pathway in strain ToN1^T, while gluconeogenesis proceeds via the reverse EMP-pathway in strains ToN1^T, PbN1^T, and EbN1^T. The diazotrophic, endophytic lifestyle of closest related genus Azoarcus is known to be associated with nitrogenase and type-6 secretion system (T6SS). By contrast, strains ToN1^T, PbN1^T, and EbN1^T lack nif genes for nitrogenase (including cofactor synthesis and enzyme maturation). Moreover, strains PbN1^T and EbN1^T do not possess tss genes for T6SS, while strain ToN1^T does and facultative endophytic “Aromatoleum” sp. CIB is known to even have both. These findings underpin the functional heterogeneity among Aromatoleum members, correlating with the high plasticity of their genomes.

The effect of combined cometabolism and gamma irradiation treatment on the biodegradability of diclofenac and sulfamethoxazole

Diclofenac and sulfamethoxazole are poorly degradable when using activated sludge or biofilm biomass in biological wastewater treatment. However, a biological phenomenon called cometabolism can improve the removal efficiency, especially in activated sludge treatment. In the case of cometabolism an easily degradable substrate is added to the wastewater under treatment. Such easily degradable molecules (e.g. methanol, acetic acid, ethylene glycol) also form in the anaerobic wastewater treatment steps and are utilized as substrates. The rate of oxidative biodegradation of pharmaceuticals (measured by using oxygen uptake rate) was shown to greatly increase in the presence of easily degradable substrates in activated sludge treatment. However, in biofilm treatment the rate of cometabolism remained low, because biofim biomass has much narrower bacterial diversity than activated sludge. The oxidation rate on biofilm was found to increase considerably by using an advanced oxidation process, ionizing radiation treatment, before cometabolism. This combined treatment, irradiation and cometabolism is recommended for the degradation of recalcitrant organic compounds on biofilm.

Fenton process in dispersed systems for industrial wastewater treatment

Industrial wastewater contains recalcitrant organic compounds with a very complex chemical structure, built of molecules with long chains of carbon atoms and attached different functional groups. Chemical or biological treatments used for removal of these compounds are being replaced with more efficient non-commercial wastewater treatments. Advanced oxidation processes overcome limitations of conventional methods regarding formation of by-products during degradation of recalcitrant organic compounds. The Fenton process, or use of the Fenton?s reagent, has became one of the most utilized processes due to simplicity, economy and accessible amounts of ferrous iron and hydrogen-peroxide, which are used in the process. In specific, the Fenton?s reagent is a catalytic-oxidative mixture of these two components. The ferrous iron Fe2+ initiates and catalyzes decomposition of H2O2, resulting in generation of hydroxyl radicals, which are the main radical species in the process able to detoxify several organic pollutants by oxidation. In addition, other mechanisms besides formation of hydroxyl radicals may occur during the Fenton process and participate in degradation of target pollutants. Generally, the treatment efficiency relies upon the physical and chemical properties of target pollutants and the process operating conditions. The main disadvantage of the Fenton process is production of sludge formed by iron hydroxide at certain pH values. An alternative solution for this problem is application of this process in fluidized bed reactors. This paper presents an overview of Fenton and photo-Fenton processes in dispersed systems for removal of different industrial wastewater pollutants. The most important process parameters, required for efficient degradation of recalcitrant organic compounds are also described, such as the catalyst type, pH value, temperature, H2O2 concentration and retention time. Strict control of Fenton process parameters in fluidized bed reactors at desired values can bring these systems to the commercial use.

Enhancement of micro-filtration performance for biologically-treated leachate from municipal solid waste by ozonation in a micro bubble reactor

Abstract The degradation of recalcitrant organic compounds in biologically-treated municipal solid waste leachate (MSW) was investigated using pre-ozonation in a micro bubble reactor. The effects of operating parameters such as reactor pressure, liquid phase temperature, inlet ozone concentration and ozone flow rate on micro filtration (MF) performance were studied systematically. It is demonstrated that the MF was obviously enhanced with ozonation time before 45 min and increasing inlet ozone concentration, as well as increasing ozone flow rate. Additionally, the reactor pressure and liquid phase temperature have no obvious effects on improving MF performance. And the mechanism for the enhancement of MF performance was explored through analysis of the colloids present in the leachate by SEM and organic compounds by GC/MS. The micro flocculation effect and the reduction of hydrocarbon and heterocycle compounds in the leachate by ozonation treatment were responsible for improving the MF performance.

Oxidation of hazardous compounds by heterogeneous catalysis based on Cu/Al2O3 system in Fenton-type reactions

ABSTRACTThis review examines in detail all components involved in heterogeneous Fenton-type reactions, with special focus on copper species supported on alumina for H2O2 decomposition, their redox chemistry, and their practical advantages over traditional Fenton for the degradation of recalcitrant organic compounds. Several aspects for a deeper comprehension of the properties of γ-Al2O3 as support for catalytic applications are discussed. Iron-free systems stability after calcination and catalyst performance during the oxidation reaction are evaluated to solve the disadvantages of iron-based system. Copper species supported on alumina for H2O2 decomposition in Fenton-like reactions are examined, with special focus on their redox chemistry and practical advantages over traditional Fenton system for recalcitrant compounds degradation. Characterization techniques for the elucidation of the structures, compositions, and chemical properties of both the solids used in heterogeneous catalysis, and the adsorbates and intermediates present on the surfaces of the catalysts during reaction are explained. Global indicators for chemical characterization of wastewaters and measurement of catalytic efficiency are described.

Post-treatment of plywood mill effluent by Multi-Barrier Treatment: A pilot-scale study

Industrial wastewaters are generally discharged to water bodies after treatment. However, in most cases, industrial wastewater effluents are highly contaminated with organic matter and threaten to pollute the receiving environment. Advanced oxidation processes (AOPs) have received significant attention in recent years as a promising technology for the degradation of recalcitrant organic compounds that are not treatable by conventional techniques. The main objective of this work was to evaluate the feasibility of a Multi-Barrier Treatment (MBT) process for the post-treatment of plywood mill effluent on a pilot scale. The MBT process included filtration, an H2O2/UVC step and catalytic wet peroxide oxidation (CWPO) process using granular activated carbon (GAC). In addition, synthetic industrial wastewater (SIWW) was used to test the scaling-up parameters and performance in discontinuous and continuous mode for the H2O2/UVC process. Parameters, such as dose that was accumulated by water can be used for scaling up the H2O2/UVC process. Under optimal operational conditions (H2O2:TOC mass ratio 5) for SIWW, a similar level of organic compounds degradation can be reached at discontinuous and continuous modes of the H2O2/UVC process at an analogous UVC dose accumulated by water. The feasibility of the MBT process for the post-treatment of industrial wastewater effluent was confirmed as leading to 89%, 76%, 88.5% and 70% of suspended solids, TOC, COD and turbidity removal, respectively. The concentrations of tannic acid and H2O2 after MBT were below the detection limit, suggesting full elimination. Based on preliminary estimations, the operation and maintenance cost (O&M) of the MBT process is 0.95€m−3.

Preparation and Characterization of a Dimensionally Stable Electrocatalysts for Electrochemical Oxidation of Persistent Organic Compounds

IntroductionThe persistent organic pollutants are a growing problem of pollution. Recently, the electrochemical oxidation processes have been employed to degrade organic matter contained in water. DSA electrodes are used for oxidizing organics via oxidants electro generated on their surface, such as the hydroxyl radical (•OH) which mineralize persistent organic pollutants1. The production of •OH on DSA is performed for the no active electrode route avoiding oxygen evolution reaction. It is expected that the mixed metal oxide electrode of IrO2-SnO2-Sb3O5 favor the formation of (•OH) through the water oxidation, although the formation of this radical is uncertain2.MOx + H2O →MOx(·OH) + H+ + e- (1)In this work the synthesis of IrO2-SnO2-Sb3O5 electrode is made by Pechini method. On the other hand, the detection of •OH radicals, formed during the oxidation of water, is followed by the addition reaction between •OH radical and p-nitrosoaniline (RNO) compound. The above reaction produces a stable radical (spin trap) and the detection of •OH is determined by the bleaching of the RNO3.Experimental methodsA pretreatment of the titanium substrate is performed by applying concentrated reagent grade HCl and oxalic acid. Then, an inter-layer of titanium oxides and tantalum oxides is supported on the substrate. Afterwards, the IrO2-SnO2-Sb3O5 coating was prepared using the method Pechini2. Hydroxyl radicals are generated on IrO2-SnO2-Sb3O5 at current densities of 10, 15 and 20 mA cm-2, and these are detected in situ by the discoloration of the RNO on a UV–visible method at wavelength of 440 nm. ResultsFigure 1 shows the depletion of the absorbance of RNO with time at a wavelength range of 350-550 nm, during the electrolysis of water at 10 mA cm- 2. The bleaching of RNO put on evidence that hydroxyl radicals are produced on IrO2-SnO2-Sb3O5 owing to the reaction between RNO and MOx(•OH). Electrolysis performed at 15 mA cm- 2 (not shown herein) showed similar results to that obtained at 10 mA cm- 2; while at 20 mA cm- 2 (not shown herein) the bleaching was incomplete suggesting the apparition of oxygen evolution reaction.ConclusionsHydroxyl radical formation via water discharge on the IrO2-SnO2-Sb3O5 electrode was achieved at 10 ≤ J ≤ 15 mA cm-2. The detection of MOx(•OH) was followed by means of the addition reaction between MOx(•OH) and the RNO which produced a stable radical. The generation of MOx(•OH) radicals on the electrode IrO2-SnO2-Sb3O5 can be implemented in the degradation of recalcitrant organic compounds contained in industrial wastewater. This later should serve as a starting point for future research.

Profile of Aromatic Intermediates of Titanium Dioxide Mediated Degradation of Phenol

Photocatalysis is green technology for the degradation of recalcitrant organic compounds in water, and have found success in the removal of several water pollutants. Degradation of pollutants is often accompanied by their conversion into other compounds some of which are sometimes feared to be more environmentally harmful than the parent compound. This study profiles aromatic intermediates formed during photocatalytic degradation of phenol in a batch system. Catechol, hydroquinone and resorcinol were identified as the major aromatic degradation intermediates. Maximum concentrations of intermediates obtained is in the order catechol>resorcinol>hydroquinone with all three produced within the first two minutes of phenol degradation. Resorcinol attained steady state concentration of 3.73 mg/L after 2 minutes of phenol photocatalysis with no appreciable change in its concentrations until all phenol is degraded suggesting that production of resorcinol proceeds at approximately the same rate as its removal from solution. Catechol formed rapidly attaining maximum concentration of 7.00 – 7.11 mg/L; after 6 minutes at a rate of 0.764 – 0.868 mg/L/min; decreasing thereafter at rates of 0.241 – 0.348 mg/L/min. Maximum concentration of 0.96 – 1.66 mg/L; of hydroquinone was obtained then decreases steadily until all phenol is degraded. Complete mineralisation of phenol and intermediates was achieved under optimum reaction conditions.

Sulfate radical-based ferrous–peroxymonosulfate oxidative system for PCBs degradation in aqueous and sediment systems

Polychlorinated biphenyls (PCBs) in the environment pose long-term risk to public health because of their persistent and toxic nature. This study investigates the degradation of PCBs using sulfate radical-based advanced oxidation processes (SR-AOPs). These processes are based on the generation of sulfate radicals through iron (Fe(II), Fe(III)) mediated activation of peroxymonosulfate (KHSO5, PMS) or persulfate (Na2S2O8, PS). This study is the first instance for coupling of Fe(II)/Fe(III) with PMS for PCB degradation in aqueous and sediment systems. The high oxidation efficiencies of the free radicals (SO4−), in combination with the slow rate of consumption of the oxidants, make these processes very effective for the degradation of recalcitrant organic compounds. The effectiveness of the process was evaluated based on the degradation of a model polychlorinated biphenyl, 2-chlorobiphenyl and total organic carbon (TOC) removal. The kinetics of 2-chlorobiphenyl degradation along with the effect of oxidant and catalyst concentrations on the degradation efficiency was studied. Near complete removal of 2-chlorobiphenyl was observed when Fe(II) was used with PMS or PS. Fe(II) acts as a sulfate radical scavenger at higher concentrations indicating that there is an optimum concentration of Fe(II) that leads to most effective degradation of the target contaminant. A chelating agent, sodium citrate, was used to control the quantity of iron in the solution for activation of the oxidant. For the first time, we studied the feasibility of the activation of PMS using iron citrate complexes for PCB degradation. In the presence of sodium citrate, increase in degradation efficiency was observed up to a metal:ligand ratio of 1:2, after which the increase in citrate concentration led to a decrease in removal efficiency. Fe(II)/PMS systems were found to be very effective in degrading PCB in a sediment-slurry system with more than 90% PCB removal being observed within 24h.