The mineralization of oxalic acid and bio-treated coking wastewater by catalytic ozonation using nickel oxide

Catalytic ozonation of reverse osmosis concentrate from coking wastewater reuse by surface oxidation over Mn-Ce/γ-Al2O3: Effluent organic matter transformation and its catalytic mechanism

Degradation of organics in high-salinity wastewater is beneficial to meeting the requirement of zero liquid discharge for coking wastewater treatment. Creating efficient and stable performance catalysts for high-salinity wastewater treatment is vital in catalytic ozonation process. Compared with ozonation alone, Mn and Ce co-doped γ-Al2O3 could remarkably enhance activities of catalytic ozonation for chemical oxygen demand (COD) removal (38.9%) of brine derived from a two-stage reverse osmosis treatment. Experimental and theoretical calculation results indicate that introducing Mn could increase the active points of catalyst surface, and introducing Ce could optimize d-band electronic structures and promote the electron transport capacity, enhancing HO• bound to the catalyst surface ([HO•]ads) generation. [HO•]ads plays key roles for degrading the intermediates and transfer them into low molecular weight organics, and further decrease COD, molecular weights and number of organics in reverse osmosis concentrate. Under the same reaction conditions, the presence of Mn/γ-Al2O3 catalyst can reduce ΔO3/ΔCOD by at least 37.6% compared to ozonation alone. Furthermore, Mn-Ce/γ-Al2O3 catalytic ozonation can reduce the ΔO3/ΔCOD from 2.6 of Mn/γ-Al2O3 catalytic ozonation to 0.9 in the case of achieving similar COD removal. Catalytic ozonation has the potential to treat reverse osmosis concentrate derived from bio-treated coking wastewater reclamation.

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.

Advanced treatment of industrial wastewater by ozonation with iron-based monolithic catalyst packing: From mechanism to application

An Fe-based catalyst was prepared by oxidising waste Fe shavings directly in a solution. In engineering applications, Fe shavings were compressed and modified to form Fe-based monolithic catalyst packing. Both of which exhibited excellent catalytic activity in catalytic ozonation industrial wastewater after biochemical treatment. Fe-based monolithic catalyst packing has irregular channels, large porosity, small pore diameter, and the effective specific surface area (SSA) up to 3500 m²/m³, these characteristics are conducive to mass transfer, and promote the effective utilisation of •OH in the catalyst "action zone". A tower reactor (<3000 m³/d) and reinforced concrete construction reactor (>5000 m³/d) were designed according to the wastewater flow. Regression analysis showed that hydraulic residence time (HRT) and O₃/COD_in are important parameters in engineering design and operation. In addition, strategies for the application of Fe-based monolithic catalyst packing to wastewater with high salinity and high inorganic carbon concentration have been proposed. Fe-based monolithic catalyst packing catalytic ozonation is a relatively cost-effective and eco-friendly process with extremely broad application prospects in the advanced treatment of industrial wastewater.

Ni-based catalysts used in heterogeneous catalytic ozonation for organic pollutant degradation: a minireview

Among various advanced oxidation processes for wastewater treatment, heterogeneous catalytic ozonation (HCO) has a growing interest in pollutant degradation, e.g., pesticides, pharmaceuticals, cresols, detergents, polymers, dyes, and others. Direct oxidation with ozone can occur by this route or indirectly, generating reactive oxygen species through the catalytic activation of the ozone molecule. Then, many catalytic materials were evaluated, such as unsupported and supported oxides, activated carbon, nanocarbons, carbon nitride, and mesoporous materials. This review focuses on the properties and performance of Ni-based catalysts (NiO, supported NiO, Ni ferrites, and M-Ni bimetallic), emphasizing the reaction mechanisms and the importance of the reactive oxygen species in removing toxic organic compounds.

A catalytic ozonation process using MgO/persulfate for degradation of cyanide in industrial wastewater: mechanistic interpretation, kinetics and by-products

Cyanide-laden wastewaters generated from mining and electroplating industries are extremely toxic and it is of vital importance to treat them prior to discharge to receiving water resources. The present study aims to oxidize cyanide using an ozonation process catalyzed by MgO and persulfate (PS). A MgO nanocatalyst was synthesized using the sol–gel method and characterized. The results show that the synthesized catalyst had a BET surface area of 198.3 m² g⁻¹ with a nanocrystalline particle size of 7.42 nm. In the present study, the effects of different operational parameters were investigated, and it was found that the MgO/O₃/PS process is able to oxidize 100 mg L⁻¹ of cyanide after 30 min under optimum operational conditions. Cyanide degradation mechanisms in the MgO/O₃/PS process were completely investigated and the main radical species were identified using scavenging experiments. It was found that sulfate and hydroxyl radicals both contributed to the cyanide degradation in the MgO/O₃/PS process. Cyanide degradation by-products were also tracked and it was found that cyanate and ammonium species are primarily generated during the oxidation, but increase of reaction time allowed their conversion to much less toxic compounds such as nitrate and bicarbonate. Cyanide degradation was also conducted in real industrial wastewater containing 173 mg L⁻¹ of cyanide. Although there was a reduction in cyanide removal rate, the MgO/O₃/PS process was able to completely oxidize cyanide within 70 min. Finally, it can be concluded that the ozonation process catalyzed by MgO and persulfate is an efficient and reliable advanced oxidation process for removal of cyanide from industrial wastewater.

Cyanide-laden wastewaters are extremely toxic and it is of vital importance to treat them prior to discharge to receiving water resources.

Cathodes of membrane and packed manganese dioxide/titanium dioxide/graphitic carbon nitride/granular activated carbon promoted treatment of coking wastewater in microbial fuel cell

A more practical microbial fuel cell system with both catalytic cathode membrane and packed cathode of modified granular activated carbon with manganese dioxide/titanium dioxide/graphitic carbon nitride/(MnO₂/TiO₂/g-C₃N₄/GAC) was tested in treating high COD coking wastewater (>3000 or >6000 mg L^-1). The decreased system internal resistance promoted treatment efficiency and electricity generation. With microbes acclimated, the system achieved both high removals of COD and NH₄⁺-N (>96%), decreased UV₂₅₄ from 23.80 to 34.50 cm^-1 in influent to 1.11-1.42 cm^-1 in effluent. The capacity in COD removal reached 3.07 kg COD m^-3d^-1 and the maximum power density was 1680 mW m^-3 much higher than those without the packed cathode. This system is feasible for sustainable treatment of coking wastewater.

Study on the denitrification and dephosphorization of the aqueous solution by Chitosan/4A Zeolite/Zr based Zeolite

The ternary hybrid material chitosan/4A Zeolite/Zr based Zeolite was synthesized by using 4A zeolite molecular sieve, Zr-zeolite and chitosan acetic acid solution as starting materials. The prepared composite were characterized by SEM, FT-IR and XRD. The experimental conditions such as the concentration of chitosan acetic acid solution, mass ratio of mass ratio of chitosan acetic acid solution, 4A zeolite molecular sieve and Zr-zeolite functional material, the optimum calcination temperature were optimized. Under this optimum conditions, the denitrification and dephosphorization effect can reach more than 70% when pH value was at 3-9. Dynamics research results showed that the ammonia nitrogen and phosphorus removal progress by chitosan/4A Zeolite/Zr based Zeolite was in accordance could be well described by the pseudo-second-order kinetic model, and the adsorption rate is up to 6.439 g/min. The isothermal adsorption process was in accordance with Freundlich model.

Enhanced Naproxen Elimination in Water by Catalytic Ozonation Based on NiO Films

This study evaluates naproxen (NP) degradation efficiency by ozonation using nickel oxide films (NiO(F)) as a catalyst. The NiO films were synthesized by chemical vapor deposition and characterized by X-ray diffraction, scanning electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy. NP degradation was conducted for 5 min using 10 films of NiO(F) comparing against ozonation using 100 mg/L NiO powder in suspension (NiO(S)) and conventional ozonation (O3-conv). Total organic carbon analysis demonstrated a mineralization degree of 12% with O3-conv, 35% with NiO as powder and 22% with NiO(F) after 60 min of reaction. The films of NiO(F) were sequentially used 4 times in ozonation demonstrating the stability of the synthesized material, as well as its properties as a catalyst for ozonation. A proposed modeling strategy using robust parametric identification techniques allows the comparison of NP decomposition pseudo-monomolecular reaction rates.

Removal of hard COD from biological effluent of coking wastewater using synchronized oxidation-adsorption technology: Performance, mechanism, and full-scale application

Efficient removal of the non-biodegradable organics from the biological effluent of industrial wastewater is becoming more and more important with the increasing demand for stringent discharge regulation. In this study, a synchronized oxidation-adsorption (SOA) technology was proposed for the removal of hardly biodegradable COD (hard COD) from the biological effluent of coking wastewater, and its performance was verified in a full-scale coking industrial park wastewater treatment plant (Q = 5,000 m³/d). The SOA was performed by coupling oxidation by hydroxyl radical (molar ratio of Fe²⁺ to H₂O₂ of 1:1 and pH = 5.0 ± 0.2) and adsorption by in-situ-formed nano hydrolyzed Fe³⁺ particles (nano-FeOOH). The nano hydrolyzed Fe³⁺ particles formed during the SOA exhibited a much higher specific surface area (22.83 m²/g) than the particles (10.87 m²/g) formed during the polyferric sulfate coagulation (PFSC). In comparison to PFSC, SOA performed better in terms of average COD removal (39% vs 18%) from the biological effluent. Wastewater fractionation result showed that SOA performed better in the removal of the hydrophobic acid matters, which was supported by the experiment using fulvic acid as the model organics. Mechanism studies using both biological effluent and fulvic acid solution showed that more carboxylic substances were adsorbed by the in-situ-formed nano-hydrolyzed Fe³⁺ particles formed by SOA than by PFSC, which was likely due to the generation of carboxylic substances by hydroxyl radical oxidation. In the full-scale, the COD was reduced from 118.5-198.0 mg/L in the PFSC-pretreated effluent to 61.5-104.0 mg/L through SOA treatment. The SOA treatment characterized with a mild pH condition (pH 5) and low molar ratio of Fe²⁺ to H₂O₂ (1:1) is particularly suitable for the polishing purpose to remove limited amount of organic pollutants from wastewater before discharge.

Insight into the characteristics, removal, and toxicity of effluent organic matter from a pharmaceutical wastewater treatment plant during catalytic ozonation

Changes in the characteristics, removal efficiency, and toxicity of pharmaceutical effluent organic matter (EfOM) after catalytic ozonation were investigated in this study. After a 90-min treatment with a catalytic ozonation process (COP) in the presence of MnO₂ ceramsite, the total organic carbon (TOC), UV₂₅₄, colority, protein, and humic acid removal rates were 13.24%, 60.83%, 85.42%, 29.36% and 74.19%, respectively. The polysaccharide content increased by 12.73 mg/L during the COP for reaction times between 0 and ~50 min and decreased by 6.97 mg/L between 50 and ~90 min. Furthermore, 64.44% of the total colority was detected in the hydrophobic organic matter (HOM) fraction, and after the COP, and 88.69% of the colority in the HOM was eliminated. Meanwhile, only 59.18% of the colority in the hydrophilic organic matter (HIM) fraction was removed. GC-MS analysis showed that 38 organic pollutant species were completely removed, 8 were partially removed, and 7 were generated. After 90 min of COP treatment, the pharmaceutical EfOM toxicity was effectively reduced based on the higher incubation and lower mortality rates.