Utilizing 3D DOSY NMR in the characterization of organic compounds in coal chemical wastewater

Coal chemical wastewater(CCW)with the features of high toxicity and poor biodegradability is a big issue in environmental remediation,posing a great threat to aquatic ecosystems and to human beings.Such complex molecular mixtures are notoriously difficult to characterize without initial physical separation.Herein,we present the 3D diffusion ordered spectroscopy(DOSY)analysis for CCW using DOSY-COSY and DOSY-HSQC methods,the advantages of this strategy have been demonstrated in the analysis of mixtures of aliphatic oxygenates and aromatic compounds,before being implemented on a genuine CCW sample in this study.The results showed that 3D DOSY is a robust and reliable tool for providing superior resolution and virtual separation of complex pollutants,and can be used as a general approach for structural elucidation.

Overview of enhancing biological treatment of coal chemical wastewater:New strategies and future directions

Coal chemical wastewater(CCW)is a type of refractory industrial wastewater,and its treatment has become the main bottleneck restricting the sustainable development of novel coal chemical industry.Biological treatment is considered as an economical,effective and environmentally friendly technology for CCW treatment.However,conventional biological process is difficult to achieve the efficient removal of refractory organics because of CCW with the characteristics of composition complexity and high toxicity.Therefore,seeking the novel enhancement strategy appears to be a favorable solution for enhancing biological treatment efficiency of CCW.This review focuses on presenting a comprehensive picture about the exogenous enhancement strategies for CCW biological treatment.The performance and potential application of exogenous enhancement strategies,including co-metabolic substrate enhancement,biofilm filler enhancement,adsorption material enhancement and conductive mediator enhancement,were expounded.Meanwhile,the enhancing mechanisms of different strategies were comprehensively discussed from a biological perspective.Furthermore,the prospects of enhancement strategies based on the engineering performance,economic cost and environmental impact(3E)evaluation were introduced.And novel enhancement strategy based on“low carbon emissions”,“resource recycling”and“water environment security”in the context of carbon neutrality was proposed.Taken together,this review provides technical reference and new direction to facilitate the regulation and optimization of typical industrial wastewater biological treatment.

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,NH_(4)^(+)-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.

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 highpressure 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(DACMAPTAC-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.

Experimental investigation and theoretical modeling on scale behaviors of high salinity wastewater in zero liquid discharge process of coal chemical industry

Zero liquid discharge(ZLD)treatment and reuse equipment of high salinity wastewater in coal-chemical industry often occur in various types of blockage problems because of high salt content,affecting the long-term stability of the device.In this study,the effects of solution temperature,steel,reaction time and wall roughness on fouling were investigated.The changes in the contents of fouling and fouling substances were qualitatively and quantitatively analyzed by XRD and EDS respectively,and the formation of scale was observed by SEM.The results show that with temperature increasing,Q235 steel is the most difficult to scale.Scaling rate of all salt scales reaches a maximum after 12 h,and the fouling rate decreases significantly from 12 to 48 h.It gradually stabilizes at 48 to 96 h.With the roughness increasing,the thickness of fouling layer increases,and a linear relationship is presented for 1 to 10 h.By comparing actual and simulated wastewater scaling rates,the relationship between actual and simulated wastewater scaling rates is y=ax-0.494.The composition of the scale was analyzed,calcium carbonate is the main product and increases with fouling time.Based on the above-mentioned results combining literatures,the hybrid prediction model with calcium carbonate as the main product is put forward.It is discussed microscopically that calcium carbonate is converted from aragonite and vaterite in a thermodynamically metastable state to calcite in a thermodynamically stable state.

Effect of alkalinity on nitrite accumulation in treatment of coal chemical industry wastewater using moving bed biofilm reactor

Nitrogen removal via nitrite （the nitrite pathway） is more suitable for carbon-limited industrial wastewater. Partial nitrification to nitrite is the primary step to achieve nitrogen removal via nitrite. The effect of alkalinity on nitrite accumulation in a continuous process was investigated by progressively increasing the alkalinity dosage ratio （amount of alkalinity to ammonia ratio, mol/mol）. There is a close relationship among alkalinity, pH and the state of matter present in aqueous solution. When alkalinity was insufficient （compared to the theoretical alkalinity amount）, ammonia removal efficiency increased first and then decreased at each alkalinity dosage ratio, with an abrupt removal efficiency peak. Generally, ammonia removal efficiency rose with increasing alkalinity dosage ratio. Ammonia removal efficiency reached to 88% from 23% when alkalinity addition was sufficient. Nitrite accumulation could be achieved by inhibiting nitrite oxidizing bacteria （NOB） by free ammonia （FA） in the early period and free nitrous acid in the later period of nitrification when alkalinity was not adequate. Only FA worked to inhibit the activity of NOB when alkalinity addition was sufficient.

Capability of phenol-degrading biofilm

The degradation rate of phenol-degrading biofilm was studied.The biofilm of the biofilm was a kind of phenol-degrading bacteria.The bacteria was separated from coal chemical industry wastewater.The carbon source adopted four kinds of phenols,including phenol,methyl phenol,2-methyl phenol and resorcinol.Stenotrophomonas maltophilia K279a was gained.Twelve ratio of artificial phenol mixture was designed.The degradation rate of the twelve groups was all 99.9% in 16 h.The degradation rate from high to low was phenol,resorcinol,methyl phenol,2-methyl phenol.Phenol improved the degradation of the other phenols.The coal chemical wastewater contained 980 mg/L COD and 805 mg/L phenol.The degradation rate of COD and phenol was 70% and 77%,respectively.The domesticated biofilm (D) and the biofilm without domestication (WD) respectively used 45 h and 56 h.The results showed that the biofilm can be applied to the aerobic treatment process with high proportion of total phenol.

Hybrid peroxi-coagulation/ozonation process for highly efficient removal of organic contaminants

Aromatic compounds such as phenols presented widely in coal chemical industry wastewater(CCW)render the treatment facing great challenge due to their biorefractory characteristics and potential risks to the environment and human health.Ozone-based advanced oxidation processes show promising for these pollutants removal,but the mineralization via ozonation alone is unsatisfactory and not cost-effective.Herein,a hybrid peroxi-coagulation/ozonation process(denoted as PCO)was developed using sacrificial iron plate as an anode and carbon black modified carbon felt as cathode in the presence of ozonation.An enhanced phenol removal of∼100%within 20 min and phenol mineralization of∼80%within 60 min were achieved with a low energy consumption of 0.35 kWh/g TOC.In this novel process,synergistic effect between ozonation and peroxi-coagulation was observed,and beside O_(3) direct oxidation,peroxone played a dominant role for phenol removal.In the PCO process,the hydrolyzed Fe species enhanced the generation of reactive oxygen species(ROS),while•OH was dominantly responsible for pollutant degradation.This process also illustrated high resistance to high ionic strength and better performance for TOC removal in real wastewater when compared with ozonation and peroxi-coagulation process.Therefore,this process is more cost-effective,being very promising for CCW treatment.