Construction of aldehyde-based, ester-based hyper-cross-linked polar resin and its selective adsorption mechanism for phenol in coal chemical wastewater.

Efficient and precise recovery of phenol from coal chemical wastewater (CCW) poses a significant challenge, prompting the development of a novel aldehyde-based, ester-based hyper-cross-linked polar resin (DES-COOC-CHO) in this study. Two distinct functional group modification methods were employed to enhance the screening effect of the resin. SEM, FT-IR, NMR, XPS, and BET characterizations confirmed the successful construction of the hyper-cross-linked polar resin, incorporation aldehyde and ester groups, exhibiting a special surface area of 627.2 m2/g and a microporous specific surface area percentage of 29.94%. DES-COOC-CHO adhered to the pseudo-second-order kinetic model and Langmuir model (maximum adsorption capacity of 118.0 mg/g). Its adsorption of phenol was spontaneous chemisorption, monolayer adsorption. Notably, even after undergoing 20 adsorption-desorption cycles, the resin maintained a stable adsorption capacity, showcasing excellent recoverability. In the presence of phenols sharing similar properties, DES-COOC-CHO exhibited superior selectivity for phenol. In real CCW, it achieved a remarkable 90% selective removal rate of phenol. The primary selective mechanism relied on the hydrogen bonding effect facilitated by aldehyde and ester groups, coupled with microporous sieving of appropriate size. In comparison with other adsorbent materials, DES-COOC-CHO exhibited superior adsorption properties, coupled with a cost-effective preparation process, presenting significant potential for practical applications.

Biotoxicity dynamic change and key toxic organics identification of coal chemical wastewater along a novel full-scale treatment process.

It is particularly important to comprehensively assess the biotoxicity variation of industrial wastewater along the treatment process for ensuring the water environment security. However, intensive studies on the biotoxicity reduction of industrial wastewater are still limited. In this study, the toxic organics removal and biotoxicity reduction of coal chemical wastewater (CCW) along a novel full-scale treatment process based on the pretreatment process-anaerobic process-biological enhanced (BE) process-anoxic/oxic (A/O) process-advanced treatment process was evaluated. This process performed great removal efficiency of COD, total phenol, NH4+-N and total nitrogen. And the biotoxicity variation along the treatment units was analyzed from the perspective of acute biotoxicity, genotixicity and oxidative damage. The results indicated that the effluent of pretreatment process presented relatively high acute biotoxicity to Tetrahymena thermophila. But the acute biotoxicity was significantly reduced in BE-A/O process. And the genotoxicity and oxidative damage to Tetrahymena thermophila were significantly decreased after advanced treatment. The polar organics in CCW were identified as the main biotoxicity contributors. Phenols were positively correlated with acute biotoxicity, while the nitrogenous heterocyclic compounds and polycyclic aromatic hydrocarbons were positively correlated with genotoxicity. Although the biotoxicity was effectively reduced in the novel full-scale treatment process, the effluent still performed potential biotoxicity, which need to be further explored in order to reduce environmental risk.

Regulation methods and enhanced mechanism on the efficient degradation of aromatics in biochemical treatment system of coal chemical wastewater.

In order to address the problems of poor treatment effect of coal chemical wastewater (CCW) biochemical treatment system resulting in non-compliance with effluent standards and unstable operation, a combination regulation method of co-substrate metabolism and predominant flora enhancement was constructed, and the performance and mechanism of enhanced degradation of aromatics in CCW was also investigated in this study. The results showed that when the influent concentration of chemical oxygen demand (COD) and aromatics was less than 600 mg/L and 180 mg/L respectively, there was no significant effect of the combined regulation method on the enhanced treatment of aromatics, the removal rate of total organic carbon (TOC) in the system could all more than 73%; while when the influent concentration of COD increased to 800 mg/L and the aromatics concentration increased to more than 240 mg/L, the ordinary activated sludge system had collapsed. Compared with the regulation method of co-substrate metabolism alone, the combination regulation method increased the removal rate of TOC by 21%. The analysis of antioxidant enzyme activity showed that under the combination regulation method, the antioxidant enzyme activity of microorganisms was higher and their resistance to adverse environments was stronger. EPS and dehydrogenase analysis indicated that the combination regulation method was more conducive to microbial degradation of aromatics. Meanwhile, the analysis of microbial community structure showed that the aromatics degradation bacteria genera Rhodococcus, Luteococcus, etc. were enriched under the combination regulation method. The study provides a theoretical basis and technical guidance for solving the problems of unstable operation of CCW biochemical treatment systems and non-compliance with effluent standards.

Fe3O4-CuO@Lignite activated coke activated persulfate advanced treatment of phenolic wastewater from coal chemical industry.

In this study, lignite activated coke (LAC) was used as the carrier for the first time, Fe3O4-CuO composite metal oxide was used as the main active material, and the nano-scale magnetic supported composite metal oxide Fe3O4-CuO@LAC catalyst was synthesized for the first time, which can effectively activate the active oxygen in peroxodisulfate (PS). XRD, FTIR, BET, SEM, XPS and other analysis results showed that there was particulate matter with spherical structure on the surface of the active coke, and its diffraction peaks matched well with the characteristic peaks of Fe3O4 and CuO, and it was a mesoporous structure with a specific surface area of 619.090 m2 g-1. By optimizing the experimental conditions, the results showed that more than 92% of hydroquinone can be removed under the conditions of hydroquinone concentration of 50 mg/L, pH = 5, adding 0.1 g/L catalyst and 3 mmol/L PS. EPR and quenching experiments proved that there were four reactive oxygen species in the reaction system ·OH, SO4-·, O2-· and 1O2. According to the degradation products of hydroquinone detected by LC-MS, the possible degradation path was deduced which laid a foundation for solving the problem of difficult treatment of phenol-containing wastewater in coal chemical industry.

Study on the mechanism of anaerobic fluidized bed microbial fuel cell for coal chemical wastewater treatment.

The coal chemical wastewater (CCW) was treated by anaerobic fluidized bed microbial fuel cell (AFB-MFC) with macroporous adsorptive resin (MAR) as fluidized particle. Isosteric heat calculation and molecular dynamics simulation (MDS) have been performed to study the interaction between organics of CCW and MAR. The isosteric heat of MAR to m-cresol was the largest at 65.4961 kJ/mol, followed by phenol. Similarly, the diffusion coefficient of m-cresol on MAR was the largest, which was 0.04350 Å2/ps, and the results were verified by the kinetic adsorption experiments. Microbial community analysis showed that the dominant bacteria in activated sludge of MFC fed with CCW were acinetobacter, aeromonas, pseudomonas and sulfurospirillum. The synergistic cooperation of bacteria contributed to improving CCW degradation and the power generation of MFC. Headspace-gas chromatography-mass spectrometry (HS-GC-MS) was used to detect intermediate of organics in CCW. It was proved that the intermediate of m-cresol degradation was 4-methyl-2-pentanone and acetic acid, and the intermediate of phenol degradation included cyclohexanone, hydroxyhexanedither and hydroxyacetic acid. Combined with the highest occupied molecular orbital (HOMO) analysis results of organic matter obtained by molecular simulation, the degradation pathway of organic matter in CCW was predicted. The energy of organics degradation pathway was analyzed by Materials Studio (MS) software, and the control step of organics degradation was determined.

Synthesis and evaluation of cationic flocculant P(DAC-PAPTAC-AM) for flocculation of coal chemical wastewater.

In this study, a high-efficiency cationic flocculant, P(DAC-MAPTAC-AM), was successfully prepared using UV-induced polymerization technology. The monomer Acrylamide (AM): Acryloxyethyl Trimethyl ammonium chloride (DAC): methacrylamido propyl trimethyl ammonium chloride (MAPTAC) ratio, monomer concentration, photoinitiator concentration, urea content, and cationic monomer DAC:MAPTAC ratio, light time, and power of high-pressure mercury lamp were studied. The characteristic groups, characteristic diffraction peaks, and characteristic proton peaks of P(DAC-MAPTAC-AM) were confirmed by fourier transform infrared spectroscopy (FTIR), X-Ray diffraction (XRD), 1H nuclear magnetic resonance spectrometer (1H NMR), and scanning electron microscopy (SEM). The effects of dosage, pH value, and velocity gradient (G) value on the removal efficiencies of turbidity, COD, ammonia nitrogen, and total phenol by poly aluminum ferric chloride (PAFC), P(DAC-MAPTAC-AM), and PAFC/P(DAC-MAPTAC-AM) in the flocculation treatment of coal chemical wastewater were investigated. Results showed that the optimal conditions for the flocculation of coal chemical wastewater using P(DAC-MAPTAC-AM) alone are as follows: dosage of 8-12 mg/L, G value of 100-250 s - 1, and pH value of 4-8. The optimal dosage of PAFC is 90-150 mg/L with a pH of 2-12. The optimal dosage for PAFC/P(DAC-MAPTAC-AM) is as follows: PAFC dosage of 90-150 mg/L, P(DAC-MAPTAC-AM) dosage of 8-12 mg/L, and pH range of 2-6. When P(DAC-MAPTAC-AM) was used alone, the optimal removal efficiencies of turbidity, COD, ammonia nitrogen, and total phenol were 81.0%, 35.0%, 75.0%, and 80.3%, respectively. PAFC has good tolerance to wastewater pH and good pH buffering. Thus, the flocculation treatment of coal chemical wastewater using the PAFC/P(DAC-MAPTAC-AM) compound also exhibits excellent resistance and buffering capacity.

Research on a harmless treatment method for oily sludge in coal chemical wastewater and the pollutant transformation mechanism of oily sludge during the treatment process.

This study developed an ultrasound synergistic subcritical hydrothermal treatment method (U-SHT) to address the challenges posed by the high oil and water content, complex composition, and hazardous nature of oily sludge (OS) generated during the pretreatment of coal chemical wastewater. The study investigated the efficiency of this method for the harmless disposal and resource recovery of OS, and the migration-transformation mechanism of hazardous organic pollutants in OS. The findings revealed that U-SHT achieved a removal efficiency of chemical oxygen demand in OS of 91.16 %, an oil resource recovery efficiency of 96.60 %, and a residual oil rate of 0.28 %, meeting API emission standards. Further research indicated that the solubilizing effect of the surfactant on the oil enhanced the demulsifying effect of ultrasonic cavitation on the emulsified structure of OS, enabling ultrasound to efficiently release and disperse pollutants within OS. This promoted the decomposition and transformation of pollutants under subcritical hydrothermal conditions, with synergistic removal efficiencies for typical pollutants such as long-chain alkanes, polycyclic aromatic hydrocarbons, and phenols reaching 96.61 %, 97.63 %, and 97.76 %, respectively. Economic evaluation indicated that the cost of OS treatment was $29.66/m3, significantly lower than existing methods, demonstrating promising practical application prospects.

Optimizing carbon sources regulation in the biochemical treatment systems for coal chemical wastewater: Aromatic compounds biodegradation and microbial response strategies.

The complex composition of coal chemical wastewater (CCW), marked by numerous highly toxic aromatic compounds, induces the destabilization of the biochemical treatment system, leading to suboptimal treatment efficacy. In this study, a biochemical treatment system was established to efficiently degrade aromatic compounds by quantitatively regulating the dosage of co-metabolized substrates (specifically, the chemical oxygen demand (COD) Glucose: COD Sodium acetate = 3:1, 1:3, and 1:1). The findings demonstrated that the system achieved optimal performance under the condition that the ratio of COD Glucose to COD Sodium acetate was 3:1. When the co-metabolized substrate was added to the system at an optimal ratio, examination of pollutant removal and cumulative effects revealed that the removal efficiencies for COD and total organic carbon (TOC) reached 94.61 % and 86.40 %, respectively. The removal rates of benzene series, nitrogen heterocyclic compounds, polycyclic aromatic hydrocarbons, and phenols were 100 %, 100 %, 63.58 %, and 94.12 %, respectively. Research on the physiological response of microbial cells showed that, under optimal ratio regulation, co-metabolic substrates led to a substantial rise in microbial extracellular polymeric substances (EPS) secretion, particularly extracellular proteins. When the system reached the end of its operation, the contents of loosely bound EPS (LB-EPS) and tightly bound EPS (TB-EPS) for proteins in the optimal group were 7.12 mg/g-SS and 152.28 mg/g-SS, respectively. Meanwhile, the ratio of α-Helix / (ß-Sheet + Random coil) and the proportion of intermolecular interaction forces were also increased in the optimal group. At system completion, the ratio of α-Helix / (ß-Sheet + Random coil) reached 0.717 (LB-EPS) and 0.618 (TB-EPS), respectively. Additionally, the proportion of intermolecular interaction forces reached 74.83 % (LB-EPS) and 55.03 % (TB-EPS). An in-depth analysis of the metabolic regulation of microorganisms indicated that the introduction of optimal ratios of co-metabolic substrates contributed to a noteworthy upregulation in the expression of Catechol 2,3-dioxygenase (C23O) and Dehydrogenase (DHA). The expression levels of C23O and DHA were measured at 0.029 U/mg Pro·g MLSS and 75.25 mg TF·(g MLSS·h)-1 (peak value), respectively. Correspondingly, enrichment of aromatic compound-degrading bacteria, including Thauera, Saccharimonadales, and Candidatus_Competibacter, occurred, along with the upregulation of associated functional genes such as Catechol 1,2-dioxygenase, Catechol 2,3-dioxygenase, Protocatechuate 3,4-dioxygenase, and Protocatechuate 4,5-dioxygenase. Considering the intricate system of multiple coexisting aromatic compounds in real CCW, this study not only obtained an optimal ratio for carbon source addition but also enhanced the efficient utilization of carbon sources and improved the capability of the system to effectively degrade aromatic compounds. Additionally, this paper established a theoretical foundation for metabolic regulation and harmless treatment within the biochemical treatment of intricate systems, exemplified by real CCW.

Advanced treatment of coking wastewater: Recent advances and prospects.

Advanced treatment of refractory industrial wastewater is still a challenge. Coking wastewater is one of coal chemical wastewater, which contains various refractory organic pollutants. To meet the more and more rigorous discharge standard and increase the reuse ratio of coking wastewater, advanced treatment process must be set for treating the biologically treated coking wastewater. To date, several advanced oxidation processes (AOPs), including Fenton, ozone, persulfate-based oxidation, and iron-carbon micro-electrolysis, have been applied for the advanced treatment of coking wastewater. However, the performance of different advanced treatment processes changed greatly, depending on the components of coking wastewater and the unique characteristics of advanced treatment processes. In this review article, the state-of-the-art advanced treatment process of coking wastewater was systematically summarized and analyzed. Firstly, the major organic pollutants in the secondary effluents of coking wastewater was briefly introduced, to better understand the characteristics of the biologically treated coking wastewater. Then, the performance of various advanced treatment processes, including physiochemical methods, biological methods, advanced oxidation methods and combined methods were discussed for the advanced treatment of coking wastewater in detail. Finally, the conclusions and remarks were provided. This review will be helpful for the proper selection of advanced treatment processes and promote the development of advanced treatment processes for coking wastewater.

Study on material structure design, selective adsorption mechanism, and application for adsorption recovery of oil substances in coal chemical wastewater.

In response to the problem of high emulsified and dissolved oils being difficult to recovery from coal chemical wastewater (CCW), this study specifically constructed a non-polar, macropore, and hydrophobic adsorption material (pSt-X) based on the main components of these two oils (aromatics and phenols) for selective recovery. The results revealed that pSt-X had an adsorption capacity of 215.52 mg/g, which had remained stable for multiple recycling sessions, with an adsorption capacity constantly above 95 %. The pSt-X has significantly larger particle size (0.7 mm-1.2 mm), which simplifies the process of adsorption regeneration and effectively prevents the loss of the adsorbent powder problem. The pSt-X adsorbent demonstrated remarkable selectivity towards dissolved and emulsified oils, exhibiting removal rates of 90.2 % and 81.7 %, respectively. Moreover, pSt-X proved remarkable selectivity in removing aromatic hydrocarbons (AHs) and phenols, with impressive removal rates of 77.8 % and 85.9 %, respectively. The selective separation mechanism of pSt-X for oil substances was further analyzed, indicating that its selective adsorption of oils was primarily driven by hydrophobic, π-π, and hydrogen bonding interactions owing to its non-polar and macropore structure and hydrophobic properties. The results of this study provide solid theoretical support for green and low-carbon recovery of oil substances in CCW and are of positive practical importance for clean production in the coal chemical industry.

Which biofilm reactor is suitable for degradation of 2,4-dimethylphenol, focusing on bacteria, algae, or a combination of bacteria-algae?

Effectively treating phenolic substances is a crucial task in environmental protection. This study aims to determine whether bacterial-algae biofilm reactors offer superior treatment efficacy compared to traditional activated sludge and biofilm reactors. The average degradation ratios of 2,4-dimethylphenol (40, 70, 150, 300, and 230 mg/L) were found to be 98 %, 99 %, 92.1 %, 84.7 %, and 63.7 % respectively. The bacterial-algae biofilm demonstrates a higher tolerance to toxicity, assimilation ability, and efficacy recovery ability. The cell membrane of Chlorella in the bacteria-algae biofilm is not easily compromised, thus ensuring a stable pH environment. High concentrations of tightly bound extracellular polymers (TB-EPS) enhance the efficacy in treating toxic pollutants, promote the stable structure. Intact Chlorella, bacilli, and EPS were observed in bacterial-algal biofilm. The structural integrity of bacteria-algae consistently enhances its resistance to the inhibitory effects of high concentrations of phenolic compounds. Cloacibacterium, Comamonas, and Dyella were the main functional bacterial genera that facilitate the formation of bacterial-algal biofilms and the degradation of phenolic compounds. The dominant microalgal families include Aspergillaceae, Chlorellales, Chlorellaceae, and Scenedesmaceae have certain treatment effects on phenolic substances. Chlorellales and Chlorellaceae have the ability to convert NH4+-N. The Aspergillaceae is also capable of generating synergistic effects with Chlorellales, Chlorellaceae, and Scenedesmaceae, thereby establishing a stable bacterial-algal biofilm system.

Investigation of the deactivation and regeneration of an Fe2O3/Al2O3•SiO2 catalyst used in catalytic ozonation of coal chemical industry wastewater.

Catalyst deactivation is an ongoing concern for industrial application of catalytic ozonation processes. In this study, we systematically investigated the performance of a catalytic ozonation process employing Fe2O3/Al2O3•SiO2 catalyst for the treatment of coal chemical industry (CCI) wastewater using pilot-scale and laboratory-scale systems. Our results show that the activity of the Fe2O3/Al2O3•SiO2 catalyst for organic contaminant removal deteriorated over time due to formation of a dense and thin carbonaceous layer on the Fe2O3 catalyst surface. EPR and fluorescence imaging analysis confirm that the passivation layer essentially inhibited the O3-catalyst interaction thereby minimizing formation of surficial •OH and associated oxidation of organic contaminants on the catalyst surface. Calcination was demonstrated to be effective in restoring the activity of the catalyst since the carbonaceous layer could be efficiently combusted during calcination to re-establish the surficial •OH-mediated oxidation process. The combustion of the carbonaceous layer and restoration of the Fe layer on the surface on calcination was confirmed based on SEM-EDX, FTIR and thermogravimetric analysis. Cost analysis indicates that regeneration using calcination is economically viable compared to catalyst replacement. The results of this study are expected to pave the way for developing appropriate regeneration techniques for deactivated catalysts and optimising the catalyst synthesis procedure.

Ball-milled magnetic sludge biochar enables fast aerobic granulation in anoxic/oxic process for the treatment of coal chemical wastewater.

Coal chemical wastewater (CCW) containing toxic and hazardous matters requires to be treated prior to discharge. Promoting the in-situ formation of magnetic aerobic granular sludge (mAGS) in continuous flow reactor process has a great potential for CCW remediation. However, long granulation time and low stability limit the application of AGS technology. In this study, Fe3O4/sludge biochar (Fe3O4/SC) with biochar matrix derived from coal chemical sludge were applied to facilitate the aerobic granulation in two-stage continuous flow reactors, containing separated anoxic and oxic reaction units (abbreviated as A/O process). The performance of A/O process was evaluated at various hydraulic retention times (HRTs) (42 h, 27 h, and 15 h). Magnetic Fe3O4/SC with porous structures, high specific surface area (BET = 96.69 m2/g), and abundant functional groups was successfully prepared by ball-milled method. Adding magnetic Fe3O4/SC to A/O process could promote aerobic granulation (85 days) and the removal of chemical oxygen demand (COD), ammonia nitrogen (NH4+-N), and total nitrogen (TN) from CCW at all tested HRTs. Since the formed mAGS had high biomass, good settling ability, and high electrochemical activities, mAGS-based A/O process had high tolerance to the decrease of HRT from 42 h to 15 h for CCW treatment. The optimized HRT for A/O process was 27 h, at which Fe3O4/SC addition can result in the increase of COD, NH4+-N and TN removal efficiencies by 2.5 %, 4.7 % and 10.5 %, respectively. Based on 16S rRNA genes sequencing, the relative abundances of genus Nitrosomonas, Hyphomicrobium/Hydrogenophaga and Gaiella in mAGS accounting for nitrification, denitrification as well as COD removal were increased during aerobic granulation. Overall, this study proved that adding Fe3O4/SC to A/O process was effective for facilitating aerobic granulation and CCW treatment.

Microbial metabolism regulation on the efficient degradation of aromatic compounds for biochemical treatment process of coal chemical wastewater in pilot scale.

At present, the common problems of biochemical treatment systems of coal chemical wastewater were the poor system stability and the difficulty in reaching COD discharge standards. Aromatic compounds were the main contributors to COD value. The effective removal of aromatic compounds was an urgent problem in the biochemical treatment systems of coal chemical wastewater. In this study, the dominant microbial strains that could degrade phenol, quinoline, and phenanthrene were isolated respectively and inoculated into the pilot scale biochemical tank of coal chemical wastewater. The regulation effect and mechanism of microbial metabolism on the efficient degradation of aromatic compounds were studied. The results indicated that the various aromatic compounds were significantly removed under the regulation of microbial metabolism, the removal efficiencies of COD, TOC, phenols, benzenes, N-CHs, and PAHs were increased by about 25%, 20%, 33%, 25%, 42%, and 45%, respectively, and their biotoxicity was also drastically reduced. Moreover, the abundance and diversity of microbial community, and the microbial activity were obviously improved, as well as the various functional strains were selectively enriched, suggesting that the regulation system could resist environmental stresses with high substrate concentration and toxicity, which could lead to more enhanced performance for aromatic compounds removal. In addition, the microbial EPS content was significantly increased, implying the formation of microbial hydrophobic cell surfaces, which could improve the bioavailability of aromatic compounds. Furthermore, the enzymatic activity analysis revealed that the relative abundance and activity of key enzymes were all obviously improved. In conclusion, multiple lines of evidence were provided to clarify the regulation mechanism of microbial metabolism on the efficient degradation of aromatic compounds for biochemical treatment process of coal chemical wastewater in pilot scale. The results laid a good foundation for realizing the harmless treatment of coal chemical wastewater.

The performance and pathway of indole degradation by ionizing radiation.

Indole is a typical recalcitrant aromatic nitrogen heterocyclic compound, which usually exists in coal chemical wastewater, and cannot be effectively removed by conventional wastewater treatment process. In this study, ionizing radiation was applied for the degradation of indole in aqueous solution. The effect of absorbed dose (1, 2, 3 and 5 kGy), initial concentration of indole (10, 20, 40 and 100 mg/L) and pH (3, 5, 7 and 9) on the degradation of indole was investigated. The results showed that the removal efficiency of indole was 99.2% at its initial concentration of 10 mg/L, absorbed dose of 2 kGy, and pH of 5. In addition, quenching experiments confirmed that three reactive species, including hydroxyl radical, hydrated electron and hydrogen radical, contributed to indole degradation. Five intermediate products were identified during indole degradation, including 3-methylindole, 3-methylinodle radicals, hydroxylation inodole, anilinoethanol and isatoic acid. The possible pathway of indole degradation was proposed. The acute toxicity and chronic toxicity of intermediate products of indole degradation were significantly reduced, except for 3-methylindole. In summary, ionizing radiation is alternative technology for the degradation of indole in coal chemical wastewater.

Biodegradation time series characteristics and metabolic fate of different aromatic compounds in the biochemical treatment process of coal chemical wastewater.

In this study, the biochemical treatment system of coal chemical wastewater (CCW) was constructed to degrade aromatic compounds. The biodegradation time series characteristics of 8 benzene series (BTEX), 6 phenols, 10 polycyclic aromatic hydrocarbons (PAHs), and 3 nitrogen heterocyclic compounds (NHCs) were detected. The aim was to clarify the storage characteristics and dynamic transformation in water, EPS, and cells of these aromatic compounds. The results showed that BTEX and NHCs were more easily degraded than PAHs and phenols. Furthermore, aromatic compounds were initially adsorbed into EPS from water by microorganisms. Then, some were degraded, and others were transferred into the cell. Finally, they were completely degraded. The percentage of surplus content with them in EPS and cells were PAHs > phenols > NHCs = BTEX. The study could lay a theoretical foundation for the regulation and harmless treatment of the CCW in the stable operation of the biochemical treatment system.

Preparation of Mn/Zn@PG Catalyst for Catalytic Oxidation Treatment of Coal Chemical Wastewater.

In this study, Mn/Zn@palygorskite (PG) catalysts with developed pores and good salt tolerance were prepared and applied to the treatment of coal chemical wastewater. A doping ratio of metal elements, calcination temperature, and calcination time was used to optimize the preparation conditions and determine the optimal preparation conditions of the Mn/Zn@PG catalysts. The catalysts, obtained under various preparation conditions, were characterized and analyzed by XRD, SEM, EDS, BET, XRF, XPS, and other techniques. Results showed that the Zn and Mn elements in the Mn/Zn@PG catalyst existed as ZnO and MnO2, respectively. The optimal working conditions of the Mn/Zn@PG catalyst for catalytic oxidation treatment of coal chemical wastewater, obtained through the optimization of working conditions, are the following: reaction time 60 min, wastewater pH = 9.28, ozone ventilation rate 0.2 L/min, catalyst filling ratio 20%. The height-to-diameter ratio of the tower was 6:1. The abrasion resistance and catalytic performance of the Mn/Zn@PG catalyst after repeated use were investigated, and the mechanism of the loss of active components of the Mn/Zn@PG catalyst was explored. The coal chemical wastewater, before and after treatment, was analyzed by UV-vis spectroscopy and 3D fluorescence spectroscopy. The hierarchical-principal component comprehensive evaluation system (AHP-PCA) was established to evaluate the catalytic ozonation process of coal chemical wastewater, so that the overall evaluation of the process performance can be achieved.

Refractory organic compounds in coal chemical wastewater treatment by catalytic ozonation using Mn-Cu-Ce/Al2O3.

A composite Mn-Cu-Ce tri-metal oxide supported on γ-Al2O3 (Mn-Cu-Ce/Al2O3) catalyst was prepared by an impregnation-calcination method and investigated in the catalytic ozonation treatment of real coal chemical wastewater (CCW). The catalyst was characterized by XRD, SEM, TEM, XRF, BET, and XPS techniques. The results showed that Mn, Cu, and Ce metal oxides were evenly distributed on the Al2O3 surface and the catalyst maintained a large surface area and a high pore volume compared with the pristine Al2O3. The synergy between Mn, Cu, and Ce oxides greatly enriched the catalytic active sites and enhanced the ozonation performance. The catalytic ozonation process with Mn-Cu-Ce/Al2O3 increased the removal rate of total organic carbon (TOC) by 31.6% compared with ozonation alone. The ketones, aromatic compounds, phenols, and nitrogen-containing heterocyclic compounds in CCW have been effectively degraded and mineralized by Mn-Cu-Ce/Al2O3 catalytic ozonation process, and its biodegradability has also been significantly improved. The experimental results of ∙OH scavengers revealed that the mechanism of Mn-Cu-Ce/Al2O3 catalytic ozonation was to promote the generation of ∙OH radicals. The catalytic activity of Mn-Cu-Ce/Al2O3 was only a slight decrease in six consecutive catalytic ozonation treatments, showing good stability. Therefore, Mn-Cu-Ce/Al2O3 can be used as a candidate catalyst for the advanced treatment of refractory organic wastewaters upon catalytic ozonation.

Combined effect of coal chemical wastewater and PC on preparing of coal-to-liquids residue-based alkali activated materials.

Aimed to achieve "waste control by waste" of coal-to-liquids (CTL) industry, coal gasification residue (CGR), the most typical CTL residue, and coal chemical wastewater (CCW) were used as aluminosilicate precursor and auxiliary activator respectively to prepare alkali activated materials (AAMs). CGR-based AAMs using a less concentrated NaOH solution than conventional, with CCW as mixing water were synthesized. The results showed that CCW benefited the compressive strength of CGR-based AAMs significantly, but demonstrating slight reduction over time. The combined effect of CCW and Portland cement (PC) supplied continuous increase of strength and eliminated the strength reduction with age. The mechanisms behind the improved performance of the AAMs due to the introduction of CCW and PC were discussed by XRD, FTIR, TG-DSC, MIP and ESEM. It was found that the increased alkali content due to the introduction of the CCW, supplied more extensive dissolution of active aluminosilicate and progressive geopolymerization of CGR. The coexistence of both N-A-S-H gel and C-A-S-H gel (originated from the introduced PC) in hardened AAM pastes reduced the proportion of pores larger than 100 nm to less than 30%, and provided denser structure.

Preparation and Characterization of Cu-Mn-Ce@γ-Al2O3 to Catalyze Ozonation in Coal Chemical Wastewater-Biotreated Effluent.

Cu-Mn-Ce@γ-Al2O3 was prepared by incipient wetness impregnation and used to catalyze ozonation in a coal chemical wastewater-biotreated effluent. The preparation factors that considerably affected the catalytic performance of Cu-Mn-Ce@γ-Al2O3, specifically metal oxide loading percentage, calcination temperature, and calcination time, were examined. The catalyst was characterized by scanning electron microscopy, energy dispersive spectrometry, X-ray diffraction, and Brunauer-Emmett-Teller analysis. The optimal catalytic ozonation operating parameters, such as ozone dosage, catalyst dosage, pH, and reaction time, were also investigated. Results showed that an optimized catalyst consisted of 17.0% CuO, 3.0% MnO2, and 2.0% CeO2 (wt.%). The optimal calcination temperature and calcination time were 600 °C and 5 h. The optimal catalytic ozonation operating parameters, including ozone dosage, catalyst dosage, pH, and reaction time, were 7, 80.0 mg/L, 20.0 mg/L, 7 and 50 min, respectively. The COD removal of biotreated effluent increased to 61% under these optimal operating conditions. Meanwhile, ozonation alone resulted in only 20% removal. This work proposes the use of easily available Cu-Mn-Ce@γ-Al2O3 catalyst and might drive the advancement of catalytic ozonation for chemical wastewater purification.