Wet oxidation of real coke wastewater containing high thiocyanate concentration

Degradation of thiocyanate by Fe/Cu/C microelectrolysis: Role of pre-magnetization and enhancement mechanism

Thiocyanate (SCN-), a non-volatile inorganic pollutant, is commonly found in various types of industrial wastewater, which is resistant to hydrolysis and has the potential to be toxic to organisms. Premagnetized iron-copper-carbon ternary micro-electrolytic filler (pre-Fe/Cu/C) was prepared to degrade SCN-. Pre-Fe/Cu/C exhibited the most significant enhancement effect on SCN- removal when magnetized for 5 min with an intensity of 100 mT, and the SCN- removal rate was the highest at an initial pH of 3.0 and an aeration rate of 1.6 L/min. The electrochemical corrosion and electron transfer in the pre-Fe/Cu/C system were confirmed through SEM, XPS, FTIR, XRD, and electrochemical tests. This resulted in the formation of more corrosion products and multiple cycles of Fe2+/Fe3+ and Cu0/Cu+/Cu2+. Additionally, density functional theory (DFT) calculations and electron paramagnetic resonance (EPR) were utilized to illustrate the oxygen adsorption properties of the materials and the participation of reactive oxygen species (1O2, ·O2-, and ·OH) in SCN- removal. The degradation products of SCN- were identified as SO42-, HCO3-, NH4+, and N2. This study introduced the use of permanent magnets for the first time to enhance Fe/Cu/C ternary micro-electrolytic fillers, offering a cost-effective, versatile, and stable approach that effectively effectively enhanced the degradation of SCN-.

Treatment of thiocyanate-containing wastewater: a critical review of thiocyanate destruction in industrial effluents

Thiocyanate is a common pollutant in gold mine, textile, printing, dyeing, coking and other industries. Therefore, thiocyanate in industrial wastewater is an urgent problem to be solved. This paper reviews the chemical properties, applications, sources and toxicity of thiocyanate, as well as the various treatment methods for thiocyanate in wastewater and their advantages and disadvantages. It is emphasized that biological systems, ranging from laboratory to full-scale, are able to successfully remove thiocyanate from factories. Thiocyanate-degrading microorganisms degrade thiocyanate in autotrophic manner for energy, while other biodegrading microorganisms use thiocyanate as a carbon or nitrogen source, and the biochemical pathways and enzymes involved in thiocyanate metabolism by different bacteria are discussed in detail. In the future, degradation mechanisms should be investigated at the molecular level, with further research aiming to improve the biochemical understanding of thiocyanate metabolism and scaling up thiocyanate degradation technologies from the laboratory to a full-scale.

Application of coke breeze for removal of colour from coke plant wastewater

Treatment of coking waste water has always been a challenge because of its complex and toxic nature. Numbers of technologies like biological treatment, advanced oxidation processes, activated carbon treatment etc. are available for removal of color and organic contaminants from wastewater. However, challenges and problems associated with application of biological, advanced oxidation methods for removal of color, chemical oxygen demand (COD), cyanides led to thrust for the development of new promising technologies. In this study, the application of coke breeze for the treatment of wastewater through adsorption has been demonstrated. A pseudo second order reaction kinetics has been observed through batch process adsorption study. Furthermore, adsorption data has found to be best fitted with the Freundlich adsorption isotherm model. Color removal efficiency of 80-90% along with COD removal efficiency of 40-50% was observed within 30 min by 120 g/L dosage of the adsorbent. The removal of phenolic and other organic compounds from coking wastewater has been measured through UV-Vis spectroscopy. The morphological changes of the adsorbent coke breeze have been captured through scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis. However, because of the significant abundance in the steel plant, cost effectiveness and applicability of the post-treated coke breeze in sintered plant as fuel, turn it into a suitable adsorbent despite of having much lower specific surface area compared to commercial activated carbon (AC). Therefore, application of the coke breeze turns it into a very promising material and the technique is sustainable towards the coke quenching effluent treatment.

Influence of Integrated Membrane Treatment on the Phytotoxicity of Wastewater from the Coke Industry

In this paper, coke wastewater that had passed through biological and integrated membrane processes (filtration on sand bed-reverse osmosis) was chosen to assess the phytotoxicity of selected industrial wastewater with regard to the test plant-Vicia faba. An innovative research technique in vitro test was conducted in a large scale phytothrone chamber on two matrices: cotton and Murashige and Skoog Basal Medium (MSBM). The toxicity of wastewater was evaluated for samples: (1) treated in the treatment plant by biological processes, (2) filtrated through a sand bed and filtrated (3) reverse osmosis (RO) membrane. The results showed that there is a noticeable correlation between increasing concentrations of wastewater and seed germination of the test plant. Although the wastewater collected from the coke plant was treated biologically, it showed very high levels of germination inhibition (90-98% for cotton matrix and 92-100% for MSBM matrix) and strong toxic effects. The wastewater collected from the coke plant showed a significantly greater phytotoxic effect compared with those obtained from the effluent treated on a sand bed and in RO. However, wastewater, even after treatment on a sand bed (reduction of COD-39%, TN-46%, TOC-42%, TC-47%, SS-50%, 16PAHs-53%), was still toxic and germination inhibition was in the range of 24-48% for the cotton matrix and 14-54% for the MSBM matrix. The toxicity of wastewater treated in the membrane process was the lowest (reduction of COD-85%, TN-95%, TOC-85%, TC-86%, SS-98%, 16PAHs-67%). The germination inhibition was in the range of 4-10% for the cotton matrix and 2-12% for the MSBM matrix. These samples are classified as non-toxic or slightly toxic to the model plant. The present study highlights the necessity of monitoring not only the basic physical and chemical indicators (including the level of toxic substances as PAHs), but also their effect on the test organisms in wastewater samples.

Synergistic effect of the presence of suspended and dissolved matter on the removal of cyanide from coking wastewater by TiO2 photocatalysis

This study assesses the influence of the presence of suspended and dissolved matter on the efficiency of TiO₂ photocatalysis for the removal of cyanide from coking wastewater. Photocatalytic processes were carried out at basic pH (pH 9) with titanium dioxide (1 g/L), artificial radiation (290-800 nm) and during different time periods (20-100 min). The first assays applied in aqueous solutions achieved promising results in terms of removing cyanide. The maximum cyanide removal obtained in coking wastewater was 89% after 80 min of irradiation in the presence of suspended and dissolved matter. The presence of suspended matter composed of coal improves the efficiency of the photocatalytic process due to the synergistic effect between carbon and TiO₂. The absence of dissolved matter also improves the process due to the minimization of the hydroxyl radical scavenging effect produced by carbonate and bicarbonate ions. On the other hand, the presence of certain species in the real matrix such as silicon increases the activity of the titanium dioxide catalyst. In consequence, the improvement achieved by the photocatalytic process for the removal of cyanide in the absence of dissolved matter is counteracted.

Selective removal of thiosulfate from thiocyanate-containing water by a three-dimensional structured adsorbent: a calcined NiAl-layered double hydroxide film

NiAl-layered double hydroxide (NiAl-LDH) platelets were uniformly grown on a porous Ni foam substrate by a facile in situ hydrothermal method.

Influence of carrier filling ratio on the performance of moving bed biofilm reactor in treating coking wastewater

This study aims to evaluate the effect of carrier filling ratio on the performance of a moving bed biofilm reactor in degrading chemical oxygen demand, phenol, thiocyanate, and ammonia from coking wastewater at 20h of hydraulic retention time. The operational experiments under different carrier filling ratios ranging from 20% to 60% were investigated. The maximum removal efficiency of 89%, 99% and 99% for COD, phenol and thiocyanate, and minimum sensitivity to the increasing contaminants concentration in the influent were achieved at 50% carrier filling ratio. The Haldane competitive substrate inhibition kinetics model was used to describe the relationship between the oxygen uptake rate of ammonium oxidizers and the concentration of free ammonium. The highest biofilm microbial community functional diversity (Shannon's diversity index, H') and evenness (Shannon's evenness index, E') were obtained at 50% carrier filling ratio in all runs using a Biolog ECO microplate.