Thiocyanate Degradation Research Articles

Peroxydisulfate activation by copper nanoparticles doped highly graphitized hollow carbon spheres for thiocyanate degradation

Thiocyanate (SCN-) is a toxic and refractory inorganic pollutant commonly found in industrial wastewater. This paper proposes an innovative solution to enhance the activation of peroxydisulfate (PDS) by designing a highly graphitized hollow carbon nanosphere structure catalyst doped with copper nanoparticles, thereby achieving efficient and complete degradation of SCN-. Specifically, the active sites and electron transfer ability of the catalyst were improved by controlling the pyrolysis temperature and acid etching time during the catalyst preparation process, thereby optimizing the PDS activation rate and SCN- degradation rate. In the optimized Cu-NPs@C/PDS system, a low dose of Cu-NPs@C-650–6 catalyst (0.2 g/L) and PDS ([PDS]0: [SCN-]0 = 3: 1) was sufficient to achieve 100 % degradation of 100 mg/L SCN- within 20 min. The non-radical oxidation pathway combined with singlet oxygen (1O2) and direct electron transfer process was identified as the main degradation mechanism of SCN-. The unique oxidation mechanism provided a higher SCN- degradation reaction rate constant (k1 = 0.39 min−1) and stronger environmental ion resistance. Density functional theory (DFT) calculations show that the CO bond is the primary PDS active site for the formation of inside-out electron delocalization, and the S atom in SCN- is a vulnerable site. This work offers technological support for the treatment of water bodies holding emerging electron-rich pollutants in addition to fresh insights into the creation of efficient catalysts for metal-carbon composites.

Oxidative degradation of thiocyanate via activation of persulfate by CuO/α-MnO2 composite: Effect of calcination temperature

In this study, a highly efficient CuO/α-MnO2 bimetallic catalyst was synthesized by hydrothermal and calcination methods and employed as a peroxydisulfate (PDS) activator for the degradation of thiocyanate (SCN−) in aqueous phase. The effect of calcination temperature on the catalytic performance of CuO/α-MnO2 and the mechanism of the CM350/PDS system were studied. Under optimal conditions, almost 100 % of SCN− (100 mg/L) was degraded within 90 min. XRD, XPS, Raman, and H2-TPR analyses revealed that the catalytic performance was enhanced in the CM350 catalyst due to the formation of M-O-Cu+-like structures (M = Mn3+, Mn4+, Cu2+) through the combination of α-MnO2 with CuO. The structures exhibit excellent redox ability and facilitate electron transfer between Cu and Mn elements, thereby improving the activation effect of PDS. Besides, the Cu1.5Mn1.5O4 generated from the high calcination temperature was not conducive to the SCN− degradation reaction. Moreover, the mechanism study indicated that SO4·-, ·OH, and the electron transfer pathway mainly accounted for the SCN− degradation. This study provides some guidance for the synthesis of PDS activation materials and the treatment of industrial wastewater by an advanced oxidation process.

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−.

Efficient degradation of thiocyanate by persulfate activation of a novel SA@Fe-Ni-C composite: Properties, mechanisms and DFT calculations

The existing microelectrolytic materials are hindered in applying advanced oxidation processes due to their poor stability and easy bonding. Therefore, ternary iron-carbon microelectrolytic microspheres (SA@Fe-Ni-C) have been prepared by a simple embedding process and used to activate persulfate (PDS) to degrade thiocyanate (SCN-). The doping of Ni not only accelerates the electron transport and promotes the effective reduction of Fe3+ but also forms the cycle system of Fe2+/Fe3+ and Ni2+/Ni3+, which ensures the high catalytic activity of the catalyst. It was found that both free radicals (SO4•-, •OH and O2•-) and non-free radicals (1O2 and electron transfer) contributed to the removal of SCN-. The DFT results showed that Fe was the leading activation site of PDS, and Ni could also promote the activation of PDS. Finally, the high stability of SA@Fe-Ni-C and its anti-interference ability were verified by 5-cycle and coexistence ion experiments. This study provides some guidance for the synthesis of new micro-electrolytic materials and the treatment of industrial wastewater by an advanced oxidation process.

Effect of biosurfactant on thiocyanate degradation by automobile service station soil isolates Brachybacterium sp. and Bacillus albus

This study investigated the effect of biosurfactants on the microbial degradation of thiocyanate (SCN−), with the aim of finding a sustainable solution for the treatment of industrial wastes containing thiocyanate and related compounds. Isolates VK8 and VT7, screened from amongst 40 automobile service station soil isolates, showed promising growth in the presence of high thiocyanate concentration (500 mg/L). Biosurfactant BS1-S1W from isolate S1W (Brucella intermedia) enhanced the degradation of SCN− by Brachybacterium sp. (VT7) and Bacillus albus (VK8) by 92% and 95%, respectively, at 200 mg/L. Biosurfactant BS2-VO6 from isolate VO6-2 (Brevundimonas naejangsanensis) caused increment in the reduction of SCN- by 88% and 80%, respectively. FTIR and LC-MS analysis of the purified biosurfactants confirmed their glycolipid nature. Enhanced effect of biosurfactant was more pronounced at higher KSCN concentration. Little is known about the effects of microbial products on the enhancement of microbial biodegradation of SCN−. Production and application of biosurfactant from B. naejangsanensis has not been reported earlier and hence can lead to more effective biological agents of enhanced biomedical and environmental relevance. This is the first report of the application of Brachybacterium and B. albus for thiocyanate degradation and the effect of biosurfactant on the same.

The isolation of rumen enterococci strains along with high potential utilizing cyanide

Cyanogenic glycosides in forage species and the possibility of cyanide (CN) poisoning can have undesirable effects on ruminants. The literature estimates that unknown rumen bacteria with rhodanese activity are key factors in the animal detoxification of cyanogenic glycosides, as they are capable of transforming CN into the less toxic thiocyanate. Therefore, identifying these bacteria will enhance our understanding of how to improve animal health with this natural CN detoxification process. In this study, a rhodanese activity screening assay revealed 6 of 44 candidate rumen bacterial strains isolated from domestic buffalo, dairy cattle, and beef cattle, each with a different colony morphology. These strains were identified as belonging to the species Enterococcus faecium and E. gallinarum by 16S ribosomal DNA sequence analysis. A CN-thiocyanate transformation assay showed that the thiocyanate formation capacity of the strains after a 12 h incubation ranged from 4.42 to 25.49 mg hydrogen CN equivalent/L. In addition, thiocyanate degradation resulted in the production of ammonia nitrogen and acetic acid in different strains. This study showed that certain strains of enterococci substantially contribute to CN metabolism in ruminants. Our results may serve as a starting point for research aimed at improving ruminant production systems in relation to CN metabolism.

The efficient utilization of thiocyanate on simultaneous removal of ammonium and nitrate through thiosulfate-driven autotrophic denitrifiers and anammox

The efficient utilization of thiocyanate remain be an important bottleneck in the low-cost nitrogen removal for wastewaters containing thiocyanate. The study aimed to investigate the feasibility of thiocyanate in removal of nitrate and ammonium through anammox (AN) and thiosulfate-driven autotrophic denitrifiers (TSAD). The results showed that removal of nitrate and ammonium were achieved rapidly utilizing thiocyanate, which was attributed to degradation of thiocyanate by TSAD and cooperation with AN. The utilization efficiency of thiocyanate in nitrogen removal was increased by 250% due to the microbial cooperation. Excess thiocyanate and ammonium did not influence the nitrogen removal amount. However, the nitrogen removal were affected obviously by the biomass ratio (XAN/XTSAD) between AN and TSAD Moreover, the dynamics related to removal of pollutants was described successfully by a modified Monod model with time constraints. These findings offer an insight for efficient utilization of thiocyanate in nitrogen removal via microbial cooperation.

Molecular level insight of thiocyanate degradation by Pseudomonas putida TDB-1 under a high arsenic and alkaline condition

It is a big challenge to bioremediate thiocyanate pollution in the gold extraction heap leaching tailings and surrounding soils with high contents of arsenic and alkali. Here, a novel thiocyanate-degrading bacterium Pseudomonas putida TDB-1 was successfully applied to completely degrade 1000 mg/L thiocyanate under a high arsenic (400 mg/L) and alkaline condition (pH = 10). It also leached the contents of thiocyanate from 1302.16 to 269.72 mg/kg in the gold extraction heap leaching tailings after 50 h. The maximum transformation rates of S and N in thiocyanate to the two finial products of SO42− and NO3− were 88.98 % and 92.71 %, respectively. Moreover, the genome sequencing confirmed that the biomarker gene of thiocyanate-degrading bacterium, CynS was identified in the strain TDB-1. The bacterial transcriptome revealed that critical genes, such as CynS, CcoNOQP, SoxY, tst, gltBD, arsRBCH and NhaC, etc. in the thiocyanate degradation, S and N metabolisms, and As and alkali resistance were significantly up-regulated in the groups with 300 mg/L SCN− (T300) and with 300 mg/L SCN− and 200 mg/L As (TA300). In addition, the protein-protein interaction network showed that the glutamate synthase encoding by gltB and gltD served as central node to integrate the S and N metabolism pathways with thiocyanate as substrate. The results of our study provide a novel molecular level insight for the dynamic gene expression regulation of thiocyanate degradation by the strain TDB-1 with a severe arsenic and alkaline stress.

Green and efficient synthesis of hierarchical porous carbon derived from MOF-235 for catalytic degradation of thiocyanate

Thermal-assisted ball milling is a novel method for the green and efficient synthesis of MOF-235. MOF-235-derived porous carbon exhibits excellent catalytic performance in thiocyanate degradation by persulfate activation.

A newly developed consortium with a highly efficient thiocyanate degradation capacity: A comprehensive investigation of the degradation and detoxification potential

Thiocyanate-containing wastewater harms ecosystems and can cause serious damage to animals and plants, so it is urgent to treat it effectively. In this study, a new efficient thiocyanate-degrading consortium was developed and its degradation characteristics were studied. It was found that up to 154.64 mM thiocyanate could be completely degraded by this consortium over 6 days of incubation, with a maximum degradation rate of 1.53 mM h−1. High-throughput sequencing analysis showed that Thiobacillus (77.78%) was the predominant thiocyanate-degrading bacterial genus. Plant toxicology tests showed that the germination index of mung bean and rice seeds cultured with media obtained after thiocyanate degradation by the consortium increased by 94% and 84.83%, respectively, compared with the control group without thiocyanate degradation. Cytotoxicity tests showed that thiocyanate without degradation significantly decreased the Neuro-2a cell activity and mitochondrial membrane potential; induced reactive oxygen species generation and apoptosis; increased the cellular Ca2+ concentration; and damaged the cell nucleus and DNA. Furthermore, the thiocyanate degradation products produced the consortium were almost totally non-toxic, revealing the same characteristics as those of the control using distilled water. This study shows that the consortium has a high degradation efficiency and detoxification characteristics, as well as great application potential in bioremediation of industrial thiocyanate-containing wastewater.

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.

Enhanced biodegradation of thiocyanate by immobilized Bacillusbrevis

Biodegradation of Thiocyanate by Free and Immobilized Bacillus brevis was explored. Lignite carbon and Alginate beads have been used as immobilization matrices to study the degradation of thiocyanate with immobilized cells. The rate of thiocyanate degradation is found to be higher by immobilized cells. Cells on lignite carbon matrix are more efficient than cells on alginate beads. The tolerance of the bacteria to the toxic chemical increases by immobilization. Degradation of 100 ppm of thiocyanate was achieved in 20 h by immobilized Bacillus brevis onto lignite carbon. Reduced cost and simplicity make this technique very useful for wastewater treatment.

Coke-oven wastewater treatment in a dual-chamber microbial fuel cell with thiocyanate-degrading biofilm enriched at the air cathode

Abstract Coke-oven wastewater is usually treated with the activated sludge process, which requires large amounts of electrical energy for aeration and sludge disposal. A more sustainable treatment is strongly required. Recently, microbial fuel cells (MFCs) are focused as a technology for the production of electricity from wastewaters with simultaneous removal of organic matter. However, no MFC has been reported that can remove phenol, thiosulfate and thiocyanate simultaneously without aeration. Phenol can generally be removed well, whereas thiocyanate is relatively difficult to degrade. In this study, a dual-chamber MFC (D-MFC) was designed and equipped with a thiocyanate-degrading biofilm enriched on an air cathode. The D-MFC degraded phenol and thiosulfate in the anode chamber at the rate of 104 and 331 mg/L/day, respectively and subsequently degraded thiocyanate in the cathode chamber at the rate of 250 mg/L/day. The D-MFC showed high thiocyanate degradation rate. This suggests that pre-enrichment could accelerate thiocyanate degradation in MFC. In addition, thiocyanate degradation was not inhibited by phenol as thiocyanate was removed in the cathode chamber after phenol was removed in the anode chamber. This study demonstrated the feasibility of treating coke-oven wastewater by a D-MFC with a thiocyanate-degrading biofilm enriched at the air cathode.

Metabolic engineering of Oryza sativa for complete biodegradation of thiocyanate

Industrial thiocyanate (SCN−) waste streams from gold mining and coal coking have caused serious environmental pollution worldwide. Phytoremediation is an efficient technology in treating hazardous wastes from the environment. However, the phytoremediation efficiency of thiocyanate is very low due to the fact that plants lack thiocyanate degradation enzymes. In this study, the thiocyanate hydrolase module was assembled correctly in rice seedlings and showed thiocyanate hydrolase activity. Rice seedlings engineered to express thiocyanate degrading activity were able to completely remove thiocyanate from coking wastewater. Our findings suggest that transforming the thiocyanate hydrolase module into plants is an efficient strategy for rapid phytoremediation of thiocyanate in the environment. Moreover, the rice seedlings expressing apoplastic or cytoplasmic targeted thiocyanate hydrolase module were constructed to compare the phytoremediation efficiency of secretory/intracellular recombinant thiocyanate hydrolase. The most obvious finding from this study is that the apoplastic expression system is more efficient than the cytoplasm expression system in the phytoremediation of thiocyanate. At last, this research also shows that the secreted thiocyanate hydrolase from engineered rice plants does not influence rhizosphere bacterial community composition.

Cyclic degradation of thiocyanate in cyanide barren solution by manganese oxides

This study describes the degradation of thiocyanate by manganese oxides. With NaOH and CaO as precipitating agents, two manganese oxides, i.e. MnOx/Na and MnOx/Ca, were prepared using MnSO4·H2O as Mn resource and air as oxidant. The influence of various reaction parameters like pH, manganese oxide dosage and initial thiocyanate concentration were systematically investigated with MnO2 as a reference. Based on an entire process dynamics model and the initial kinetics analysis, the rate-limiting step (formation of the precursor complexes) and reaction orders were derived independently. The reaction pathway was detected and the formation of the precursor complexes between surface positively charged manganese oxides and thiocyanate was the first step of thiocyanate degradation, after which electron transfer occurred within the precursor complexes and intermediate products were formed, which were rapidly released to produce SO42− and CN−, and some of the CN− would be further oxidized to HCO3− and NH4+. The formation of precursor complexes is related to the charge distribution on the surface of the manganese oxide and the protonation of thiocyanate in solution, which makes the lower pH favorable. The results of cyclic treatment of cyanide barren solution showed good regenerability of MnOx/Ca and gradual reduction of undesired secondary salts (especially SO42− ions) in the degraded liquid, which made it a potentially reliable technique to regulate the thiocyanate concentration during the cyanidation process of gold ores economically.

Photochemical degradation of thiocyanate by sulfate radical-based advanced oxidation process using UVС KrCl-excilamp

The degradation of thiocyanates (SCN−) by UV-C-activated persulfate (PS) in the presence of ferric ion (Fe3+) was investigated. As a source of monochromatic far-UV-C irradiation (222 nm), mercury-free KrCl excimer lamp was used. Results showed that compared with direct photolysis, UVC/ PS and PS/ Fe3+, the combined UVC/ PS/ Fe3+ treatment had the highest initial reaction rate ω0 and removal efficiency. 99.99% conversion of thiocyanates (100 mg/L of initial concentration) was achieved in 40 min. The addition of Fe3+ in the UVC/ PS treatment was found to reduce energy consumption (calculated as amount of oxidized thiocyanates per consumed electrical energy) by 4.5 times, while only a 30% difference between direct photolysis and UVC/ PS was observed. The high efficiency of the UVC/ PS/ Fe3+ process revealed a synergistic effect (synergy index ƒ = 1.98). The effect of the initial SCN−, PS, and Fe3+ molar ratios and UV-C exposure time on SCN− removal in UVC/ PS/ Fe3+ was further investigated. It was found that at molar ratios [S2O82–]:[SCN−] = 3:1 and [S2O82–]:[Fe3+] = 1:0.1, effective decomposition of SCN− in a wide initial concentration range (from 50 to 500 mg/L or 0.86–8.6 mM) can be achieved. The strong role of •OH and SO4•− in the removal of SCN− was confirmed by the addition of radical scavengers. It was demonstrated that the presence of Cu2+ in simulated gold mine wastewater effluents neutralizes the inhibitory effects that S2O32– and NH4+ have on the degradation process.

Research Progress on Microbial Degradation of Thiocyanate in Wastewater

Research Progress on Microbial Degradation of Thiocyanate in Wastewater

Degradation of thiocyanate by electrochemical oxidation process in coke oven wastewater: Role of operative parameters and mechanistic study

This study presents the removal of thiocyanate (SCN−) from coke oven wastewater by the electrooxidation (EO) process. Initially, the performances boron-doped diamond (BDD) and different DSA (Dimensionally stable anode) electrodes including Ti/IrO2, Ti/IrO2−RuO2, and Ti/IrO2−RuO2−TiO2 in SCN− removal were compared. BDD anode outperformed the Ti−based mixed metal oxide (MMO) anodes achieving 96.51% SCN− removal efficiency. The most favorable conditions for the removal of SCN− using BDD anode were determined as follows: pH = 9, current density = 43.10 A m−2, and the electrolyte concentration (Na2SO4) = 2.5 g L−1. The strong role of ⦁OH in the removal of SCN− was confirmed by the addition of radical quenching agents. The evolution of the intermediates as a result of the EO of SCN− was determined. Under the determined conditions, the EO process could remove 84.13% of SCN− and 94.67% of phenol from a real coke oven wastewater, which was comparable to that of the simulated solution. The electrical energy consumption cost of the process to remove 1 kg of SCN− was calculated as 0.208 US $. Overall, the study showed the EO using BDD anode is a cost-effective method for the removal of SCN− from a coke oven wastewater.

Characterisation of thiocyanate degradation in a mixed culture activated sludge process treating coke wastewater

Microbial degradation of thiocyanate (SCN−) has been reported to suffer from instability highlighting the need for improved understanding of underlying mechanisms and boundaries. Respirometry, batch tests and DNA sequencing analysis were used to improve understanding of a mixed culture treating coke wastewater rich in SCN−. An uncultured species of Thiobacillus was the most abundant species (26%) and displayed similar metabolic capabilities to Thiobacillus denitrificans and Thiobacillus thioparus. Thiocyanate was hydrolysed/oxidised to NH4+-N, HCO3− and SO42−. Nevertheless, at 360–2100 mg SCN−/L a breakdown in the degradation pathway was observed. Respirometry tests demonstrated that NH4+-N was inhibitory to SCN− degradation (IC50: 316 mg/L). Likewise, phenol (180 mg/L) and hydroxylamine (0.25–16 mg/L) reduced SCN− degradation by 41% and ca. 7%, respectively. The understanding of the SCN− degradation pathways can enable stable treatment efficiencies and compliance with effluent of <4 mg SCN/L, required by the Industrial Emissions Directive.

Microbial (Enzymatic) Degradation of Cyanide to Produce Pterins as Cofactors.

Cyanide is one of the most poisonous substances in the environment, which may have originated from natural and anthropogenic sources. There are many enzymes produced by microorganisms which can degrade and utilize cyanide. The major byproducts of cyanide degradation are alanine, glutamic acid, alpha-amino-butyric acid, beta-cyanoalanine, pterin etc. These products have many pharmaceutical and medicinal applications. For the degradation of cyanide, microbes produce necessary cofactors which catalyze the degradation pathways. Pterin is one of the cofactors for cyanide degradation. There are many pathways involved for the degradation of cyanide, cyanate, and thiocyanate. Some of the microorganisms possess resistance to cyanide, since they have developed adaptive alternative pathways for the production of ATP by utilization of cyanide as carbon and nitrogen sources. In this review, we summarized different enzymes, their mechanisms, and corresponding pathways for the degradation of cyanide and production of pterins during cyanide degradation. We aim to enlighten different types of pterin, its classification, and biological significance through this literature review.