Mineral Processing Wastewater Research Articles

A high-efficiency clay mineral based organic photocatalyst towards photodegradation of butyl xanthate in mineral processing wastewater

The organic solar cell active layer, well known for excellent visible light response capability, is regarded as a potential candidate for photocatalytic degradation of organic wastewater. However, the poor dispersibility in water due to its hydrophobicity property severely limited the degrading efficiency. In this work, a novel composite photocatalyst PM6:IDT8CN-M/CK2 with a broad visible absorption spectrum and non-toxicity was first synthesized through the intercalation compounding method. A good dispersibility of PM6:IDT8CN-M in wastewater was achieved with the help of rich interlamellar porosity and good hydrophilicity of calcined kaolin. This composite photocatalyst was successfully applied to the SBX photocatalytic degradation in mineral processing wastewater, and the SBX pollutants can be completely degraded within 10 min under the condition of visible light irradiation. Compared with other reported photocatalysts, the photocatalytic degradation efficiency of SBX was dramatically improved by at least seven times. Moreover, PM6:IDT8CN-M/CK2 has remarkable stability, sustaining degradation efficiencies of over 90 % in 60 cycles. Notably, the organic solar cell active layer in PM6:IDT8CN-M/CK2 can achieve carrier rapid separation and transport, enhancing the generation of active oxides (∙O2–, and ∙OH, etc.). At the same time, the large surface area of PM6:IDT8CN-M/CK2 provides a suitable environment for the oxidation reaction of active radicals with SBX to achieve this efficient photocatalytic degradation. Overall, this work not only extends the application scope of organic solar cell active layer, but also develops a high-efficiency SBX removal technique for the treatment of mineral processing wastewater.

Activation flotation of lime-depressed pyrite with carbon dioxide: Performances, mechanism and pilot-scale application

Activation flotation of lime-depressed pyrite by sulfuric acid (H2SO4) is usually accompanied by safety hazards and environmental pollution. Exploring eco-friendly, economical and effective activator to replace H2SO4 holds great significance for the sustainable development of mining industry. In this study, carbon dioxide (CO2) as a potential activator was applied in activation flotation of lime-depressed pyrite. Micro-flotation experiments results showed CO2 significantly improved the floatability of pyrite, and a maximum recovery of 93.94% was achieved under optimal operating conditions. The activation mechanism was investigated by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Results indicated the depression of pyrite by lime was attributed to the formation of iron oxide/hydroxide species and calcium film, and CO2 effectively eliminated these hydrophilic compounds from the surface of pyrite, thus promoted the adsorption of xanthate onto the pyrite surface. Moreover, the anodic oxidation of xanthate on pyrite and the influence of CO2 on this process were investigated by cyclic voltammetry measurements. It was found that xanthate oxidation to form dixanthogen was more likely to occur in the presence of CO2, and this reaction replaced pyrite surface oxidation as the dominant anodic process. Finally, pilot-scale experiments were successfully conducted and the recovery of pyrite reached 93.18%, surpassing the ore dressing index of using H2SO4 as activator in actual production at the same period. Moreover, the concentration of sulfate ions in mineral processing wastewater was significantly reduced, and the annual cost of activator can be saved by 0.52 million RMB. The new process of activation flotation pyrite with CO2 has prospects for large-scale application in terms of activation performance, cost-effectiveness and environmental impact.

Ultrafast photosensitized degradation of xanthates by using methylene blue as photosensitizer under simulated and natural solar light irradiation: Operational parameters, mechanism and toxicity evolution

Xanthates have attracted considerable attention due to their broad applications in mineral flotation process and unique natures including environmental persistence and toxicity. This study proposed an innovative approach for the efficient xanthates treatment from mineral processing wastewater. Methylene blue (MB) with good water solubility and strong light absorption in visible range was used as the photosensitizer to degrade potassium ethyl xanthate (PEX) under homogeneous conditions. MB, even at a very low concentration (0.5 mg/L), was found to rapidly remove PEX in only 10 min whether under simulated or natural solar light irradiation. Besides, the influences of various operational parameters, including photosensitizer dosage, PEX concentration, pH, light intensity, common ions, and water source on the photosensitized oxidation process was evaluated and analyzed. The possible degradation path of PEX was investigated depending on the intermediates detected by Liquid chromatography-mass spectrometry (LC-MS), and the photosensitized degradation mechanism was further speculated and validated by the radicals quenching experiments and electron paramagnetic resonance (EPR) spectroscopy. Furthermore, the toxicity of PEX was assessed against Bullfrog tadpole and Lemna minor, and it was found to be greatly reduced after treating with MB photosensitization. Overall, it is the first time that MB is proved to be an outstanding candidate for actual flotation wastewater treatment, providing a more efficient, economical and greener alternative to conventional methods.

Electrochemical oxidation degradation of xanthate and its mechanism: Effects of carbon chain length and electrolyte type

There are a lot of residual flotation reagents such as xanthate remaining in the mineral processing wastewater, which must be deeply removed for recycling or discharge. However, there are few studies using electrochemical oxidation to remove xanthate. This article employs the electrochemical oxidation method to treat simulated xanthate-containing wastewater, which investigates the mechanisms involved in removing four xanthate homologues under different electrolyte conditions. Results show that under 1 g/L of Na2SO4, current density of 40 mA/cm2, initial pH of 7.0, and initial concentration of xanthates 1 mM, four alkyl xanthates can be completely removed within 60 min. The COD removal and TOC removal can reach 71.42%–88.61% and 54.23%–81.50%, respectively. By contrast, NaCl electrolyte is more favorable for xanthate degradation. The generated SO42− concentration can reach 145.4 mg/L at 60min, resulting in the sulfur mineralization ratio (ηs) of 75.72%. Regardless of the electrolyte type, as the carbon chain length increases, the xanthate degradation rate accelerates, accompanied by higher COD and TOC removal. The results of UV–vis spectra and LC–MS indicate that intermediate substances such as xanthate peroxides and alcohols are first formed in the process, ultimately leading to the complete mineralization of small molecule substances such as SO42−, CO2, and H2O. The fate of S and Cl elements confirms it. EPR and probe fluorescence spectroscopy results indicate that in Na2SO4 electrolyte, the main active substances are ·OH and a small amount of SO4∙–. Additionally, the production of ·OH increases as the electrolysis time is prolonged. In NaCl electrolyte, ·OH undergoes a series of reactions with Cl− to convert into Cl∙ and active chlorine, which constitute the primary reactive oxygen species.

Effects of Mg(II) doping amount on the hydration characteristics of kaolinite surface: Molecular dynamics simulations and experiments

To explore the microscopic effects of Mg(II) doping amount on the hydration characteristics of kaolinite surface, the Mg(II) ions and kaolinite were used as the subjects of research in molecular dynamics simulations and experimental verification to investigate the microscopic effects of the lattice magnesium impurity on the surface hydration of kaolinite. The results indicate that the interaction between H2O and Mg(II)-doped kaolinite (Mg(II)-Kao) surfaces, along with hydrogen bonding at the interface, gradually increase with increasing Mg(II) doping amounts, implying that Mg(II) doping significantly enhance the surface hydration of kaolinite. The hydration of the Mg(II)-doped kaolinite (001) surface (Mg(II)-Kao(001)) is stronger than that of the Mg(II)-doped kaolinite (001¯) surface (Mg(II)-Kao(001¯)) with the same Mg(II) doping amount. As the quantity of Mg(II) doping increased, the contact angle and humidity of the kaolinite surface decrease and progressively increase, respectively, signifying that the hydration level of the kaolinite surface increase. Overall, the main influence of Mg(II) doping on the surface hydration properties of kaolinite is the enhancement of hydration activity and ionic hydration. The results can provide theoretical support for further study of the real clay surface hydration mechanism, efficient treatment of clay-containing mineral processing wastewater and resource utilization of coal measure clay.

Harnessing Renewable Lignocellulosic Potential for Sustainable Wastewater Purification.

Utilizing renewable lignocellulosic resources for wastewater remediation is crucial to achieving sustainable social development. However, the resulting by-products and the synthetic process characterized by complexity, high cost, and environmental pollution limit the further development of lignocellulose-based materials. Here, we developed a sustainable strategy that involved a new functional deep eutectic solvent (DES) to deconstruct industrial xylose residue into cellulose-rich residue with carboxyl groups, lignin with carboxyl and quaternary ammonium salt groups, and DES effluent rich in lignin fragments. Subsequently, these fractions equipped with customized functionality were used to produce efficient wastewater remediation materials in cost-effective and environmentally sound manners, namely, photocatalyst prepared by carboxyl-modified cellulose residue, biochar-based adsorbent originated from modified lignin, and flocculant synthesized by self-catalytic insitu copolymerization of residual DES effluent at room temperature. Under the no-waste principle, this strategy upgraded the whole components of waste lignocellulose into high-value-added wastewater remediation materials with excellent universality. These materials in coordination with each other can stepwise purify high-hazardous mineral processing wastewater into drinkable water, including the removal of 99.81% of suspended solids, almost all various heavy metal ions, and 97.09% chemical oxygen demand, respectively. This work provided promising solutions and blueprints for lignocellulosic resources to alleviate water shortages while also advancing the global goal of carbon neutrality.

Photocatalytic degradation of SBX in mineral processing wastewater with hollow CdS/MWCNTs nanocomposites

In this study, a novel hollow sphere CdS/MWCNTs composite photocatalytic material was prepared by hydrothermal method and was first used for the photocatalytic degradation of sodium butyl xanthate (SBX) in sulfide mineral processing wastewater. The morphology structure and photocatalytic properties of hollow sphere CdS/MWCNTs composite catalyst were studied by scanning electron microscopy (SEM), X-ray diffraction (XRD), ultraviolet-visible diffuse reflectance spectroscopy (UV–vis DRS), thermogravimetric analysis (TGA) and photocatalytic activity experiments. The results showed that 15 mg CdS/MWCNTs with the 5 % MWCNTs doping amount possessed the highest photocatalytic degradation efficiency for SBX which the degradation rate reach 99 %. The hollow sphere structure and addition of MWCNTs obviously improved the migration and separation of photogenerated electrons (e−) and holes (h+) of pure CdS, leading to high photocatalytic efficiency.

Electrochemical activation of peroxydisulfate by Ti/IrTaO2 anode for quick degradation of xanthate

High concentrations of residual xanthate in mineral processing wastewater often limit the reuse of tailing water. Targeted removal of xanthate is an effective strategy for improving the tailing water recycling rate. In this study, the degradation efficiency and mechanism of sodium ethyl xanthate (SEX) in an electroactivated peroxydisulfate (EAPDS) system were investigated systematically. To avoid the influence of co-existing organic and inorganic matters in real flotation wastewater, we used simulated SEX wastewater to conduct the efficiency and mechanism investigation. A significant synergistic effect between electrocatalysis and peroxydisulfate was observed during the SEX decomposition. When the initial concentration of SEX was 200 mg/L, it achieved 100% removal rate only in 30 min with PDS dosage of 5 mM at current density of 10 mA/cm2. The introduction of peroxydisulfate boosted the removal efficiency six-fold compared to electrocatalysis alone. UV-Vis spectroscopy and GC-MS analyses revealed that the intermediate products of SEX were C2H5OH and CS2. The reactive oxygen species induced in the EAPDS were identified using a series of detection methods. •OH, 1O2, h+, O2•− and electron transportation process (ETP) all contributed to SEX removal. The degradation mechanism in the EAPDS system was proposed based on the analysis of the reactive oxygen species and products. Application to real flotation wastewater was attempted as well. The effects of different operating conditions were also evaluated, including pH, coexisting anions, PDS dosage, and current density. This study provides a new approach for the rapid removal of residual xanthates from mineral processing wastewater.

Constructing 3D flower-like S-scheme N–Bi2O2CO3/g-C3N4 heterojunction with enhanced photocatalytic performance

Mineral processing wastewater contains a lot of organic matter and heavy metal ions, and poor self-degradation ability makes it a key treatment object in environmental treatment. Photocatalysis is a promising technology to efficiently mineralize refractory contaminants from wastewater. In this work, 3D flower-like S-scheme N–Bi2O2CO3/g-C3N4 heterostructures were successfully constructed by hydrothermal method with the auxiliary of ionic liquids. The photocatalytic experiments show that the catalytic activity of heterojunction photocatalysts was significantly higher than that of bare g-C3N4 and N–Bi2O2CO3 for the degradation of two pollutants. NBOC/CN-2 shows the highest photocatalytic performance, and the degradation efficiency of sodium isobutyl xanthate (SIBX) on NBOC/CN-2 is 1.85 and 3 times that of bare g-C3N4 and Bi2O2CO3, respectively. The degradation efficiency of m-Cresol on NBOC/CN-2 is 8.34 and 6.93 times that of bare g-C3N4 and N–Bi2O2CO3, respectively. This significantly enhanced photocatalytic activity is attributed to the formation of flower-like heterojunctions, which can greatly increase the specific surface area and facilitate the separation and migration of photogenerated carriers. Total organic carbon (TOC) experiment proves that the two pollutants are effectively mineralized under the action of the prepared photocatalyst. The degradation path of m-Cresol degradation products was inferred based on the ion fragments. The capture experiment and Nitro-blue tetrazolium (NBT)-•O2− measurement show that superoxide radical plays a major role in photocatalytic degradation. The outstanding stability of the prepared flower-like heterojunction samples was examined by cyclic experiments. The S-scheme charge transfer mechanism has been proposed to explain the boosted activity of the flower-like heterojunction photocatalyst. This work provides a new idea for the design of efficient and stable g–C3N4–based photocatalyst for the photocatalytic degradation of refractory wastewater.

Preparation of g-C3N5 composites for butyl xanthate photocatalytic degradation

The nitrogen-rich graphite-phase carbon nitride (g-C3N5) supported TiO2 photocatalyst (Ti-CN) was prepared using TiO2 and 3-amino 1, 2, 4-triazole as raw materials for butyl xanthate residual (SBX) removal from mineral processing wastewater. The crystal, morphology, specific surface area and optical properties of the Ti-CN were characterized by XRD, TEM, UV–vis DRS, BET and PL. These results showed that TiO2 particles were uniformly dispersed on g-C3N5 nanosheets, and the heterojunction was formed. The formation of heterojunction improved its response to visible light, and promoted the separation of photoelectron-hole, contributing to improving its photocatalytic activity. The influence of catalyst dosage, initial SBX concentration and pH value of the SBX solution on SBX photocatalytic degradation removal was investigated. The Box-Behnken design of the response surface was used to optimize the process conditions to obtain the optimal experiment conditions with the pH of 7.04, catalyst dosage of 50.2 mg and SBX concentration of 56.6 mg/L. The SBX photocatalytic degradation removal of Ti-CN is 98.15 %, which is close to the predicted value of 97.75 % at the optimal experiment conditions. Meanwhile, the SBX degradation removal of Ti-CN still had 90.21 % after five cycles, indicating that Ti-CN has good stability. These results indicate that Ti-CN can be used as the promising photocatalyst for SBX from mineral processing wastewater.

Natural Pyrite as a Catalyst for a Fenton Reaction to Enhance Xanthate Degradation in Flotation Tailings Wastewater

The efficient treatment of mineral-processing wastewater has attracted soaring interest recently. This study’s objective was to degrade xanthate from flotation tailings wastewater using a pyrite-catalyzed Fenton system. A sodium butyl xanthate (SBX) removal rate of more than 96% was achieved via the method under optimal conditions (a H2O2 concentration of 0.5 mM, a FeS2 concentration of 0.5 g/L, an initial SBX concentration of 100 mg/L, and a natural pH of 9.36 ± 0.5), which is 12.85% higher than with a H2O2 system. An appropriate concentration of natural pyrite can act as a catalyst to significantly improve the oxidation capacity of H2O2. Additionally, the results of electron paramagnetic resonance and quenching measurements suggest that hydroxyl radicals (•OH) are the main active species in the H2O2-FeS2 system. The possible reaction mechanism is proposed. The H2O2 adsorbs onto the pyrite surfaces and reacts with Fe2+, triggering the formation of •OH and Fe3+. The •OH most likely attacks the SBX that adsorbs on the pyrite surface or exists in the solution and promotes the transformation of the SBX anion (C4H9OCS2−) into the intermediate butyl xanthate peroxide (BPX, C4H9OCS2O−). Finally, BPX intermediates are likely further oxidized to smaller products such as SO42−, CO2, and H2O under the ongoing attack of •OH.

Polydopamine-modified MOF-5-derived carbon as persulfate activator for aniline aerofloat degradation

Residual flotation chemicals in beneficiation wastewater seriously threaten local ecosystems, such as groundwater or soil, and must be treated effectively. Currently, the degradation of organic pollutants using nitrided MOFs-derived carbon to activate persulfate (PDS) has attracted considerable attention. Hence, we developed a new synthetic strategy to load dopamine hydrochloride (PDA) onto MOF-5-derived porous carbon (PC) to form NPC, and the degradation of a typical flotation Aniline aerofloat (AAF) at high salinity by a low dose of the NPC/PDS system was investigated. Several characterization analyses such as TEM, XRD, Raman, FT-IR and XPS demonstrated that the nitrogen-rich indolequinone unit in PDA provided nitrogen to PC during the pyrolysis process. This enabled the core-shell structure of NPC and the synergy among the multiple components to induce the AAF degradation by PDS over a wide pH scale in a short period of time. It was deduced that the degradation of AAF by the NPC-8/PDS system was a non-radical pathway dominated by 1O2, which relied mainly on the conversion of superoxide radicals (O2•−) and surface-bound radicals. Among them, the pyridine N in the sp2 hybrid carbon was considered as a possible active site. This non-radical pathway was resistant to pH changes and background substances in the water, and well overcame the inhibition of the reaction by natural organic substances and inorganic anions in natural water. In this study, A novel approach to the synthesis of homogeneous MOFs nuclear-derived porous carbon was proposed and the application of MOFs-derived porous carbon for AAF remediation of mineral processing wastewater was broadened.

New strategy for sustainable treatment of residual xanthate in mineral processing wastewater by using natural pyrite

Residual xanthates in mineral processing wastewater cause severe water pollution and potential air pollution in mining areas. In this work, the subsequent degradation behavior of xanthate after adsorption on pyrite surface was investigated and confirmed for the first-time using potassium ethyl xanthate (PEX) as a model xanthate collector. The influences of different parameters, including pyrite loading, pH, temperature and oxygen, on PEX degradation were examined by monitoring the PEX concentration and the hazardous by-product CS2. The results indicated that pyrite was an effective natural material for treating residual xanthates in mineral processing wastewater. The removal rate constant increased from 0.006 h−1 to 0.2024 h−1 with increasing pyrite loading, and the CS2 generated during the PEX degradation reduced from 92.11 % to 1.95 %. Acidic pH and high temperature were conducive to PEX degradation but also resulted in more CS2 generation. Dissolved oxygen played a critical role in PEX degradation by affecting the reactive oxygen species production. The activity of pyrite declined by 23.5 % when it was reused for three runs due to oxidation products accumulation. This work provided a new strategy and practical information for using nature pyrite as an eco-friendly and cost-effective material for residual xanthate degradation in mineral processing wastewater.

Enhancing photocatalytic degradation of potassium butyl xanthate in mineral processing wastewater: Novel VO2+-doped LiZnBO3 nanosheets under visible light

Metal borates have attracted significant scientific attention due to their remarkable functional properties, making them versatile materials for applications in photocatalysis and energy storage. For the current investigation, three different concentration (1, 3, and 5 mol %) of vanadyl ions doped LiZnBO3 nanosheets (VO2+-doped LZB) were synthesized by an in-situ hydrothermal method. To better understand the properties of these prepared samples, a thorough characterization has been carried out, utilizing a range of structural and optical spectroscopy techniques. This study investigated the photocatalytic performance of the synthesized materials in the context of removing the mineral pollutant potassium butyl xanthate (PBX). Remarkably, at a 3 mol % concentration, the LZB-VO3 nanocomposite displayed significantly higher photocatalytic activity, achieving an impressive PBX degradation rate of 96.58 % within a short duration of 70 min. In contrast, the pure LZB material exhibited a more modest degradation efficiency of only 30.58 % when exposed to visible light. The optimized catalyst demonstrated a maximum rate constant of 0.0392 min−1, representing a remarkable enhancement of approximately 7.13 times compared to pure LZB. These findings underscore the remarkable potential of vanadyl ion doping, as it improves the absorption of the visible light spectrum and facilitates the efficient detachment of photoinduced charges, thereby significantly enhancing overall photocatalytic activity.

Study on CuO/g–C3N4 S–Scheme heterojunction for enhanced visible-light-driven photocatalytic degradation of xanthate

Xanthate wastewater is a serious threat to the surrounding environment of mining sites, and it is important to use visible light photocatalytic technology to remove xanthatefrom wastewater. In this paper, a simple hydrothermal calcination synthesis route was used to grow submicron-sized CuO onto the surface of g-C3N4 for the degradation of xanthate in mineral processing wastewater. The results showed that the CuO/g–C3N4–0.4 composite catalyst degraded xanthate with an efficiency of 83.2% in 120 min, which was 6.2 times higher than that of pure g-C3N4. The catalyst materials were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. It was found that the excellent photocatalytic performance of the composite was attributed to the construction of S-scheme CuO/g–C3N4–Xheterojunction, which not only broadened the light absorption range but also retained the strong redox ability of holes and electrons to participate in the reaction while efficiently separating the photoinduced carriers. Based on the results of active substance capture, an S-scheme charge transfer model was proposed and the photodegradation mechanism of xanthate was reasonably elucidated.

Peroxymonosulfate Activation by Iron Sulfide Minerals for Degradation of Various Thiol Collectors in Mineral Processing Wastewater: Performance, Mechanism, and Structure–Activity Relationship

Peroxymonosulfate Activation by Iron Sulfide Minerals for Degradation of Various Thiol Collectors in Mineral Processing Wastewater: Performance, Mechanism, and Structure–Activity Relationship

Electrocoagulation in a packed aluminium scraps anode reactor for mineral processing wastewater treatment

Efficient treatment and purification of mineral processing wastewater (MPW) have not been sufficiently investigated in the past though they are of great importance for sustainable mineral processing. Herein, a unique electrocoagulation (EC) reactor with aluminium scraps as anode material was developed for the treatment of real industrial MPW containing residual flotation reagents (major contributor to chemical oxygen demand, COD) and suspended particles. It was found that the active coagulants produced from the dissolution of aluminium scraps can play a key role in the purification of MPW. Under the conditions of initial pH 9, current 1 A, and processing time 90 min, the removal rate of COD was 74% while the turbidity can be almost completely removed. The mechanism lies in that most of the flotation reagents was adsorbed on the surfaces of suspended mineral particles, namely, montmorillonite, quartz, garnet, chlorite and mica, and then precipitated with the mineral particles. This innovative technology of utilizing wasted aluminium scraps to treat MPW is in line with the green development.

Exploring the mechanistic insights of Fe3+-doped LiZnBO3 nanosheets for visible light-driven photocatalytic degradation of mineral pollutants in wastewater

Novel LiZnBO3 nanosheets doped with iron ions (Fe3+-doped LZB) were synthesized in this study using an in-situ hydrothermal technique. The doping concentrations varied (1, 3, and 5 mol%) without the use of any surfactant or template. The effectiveness of the synthesized materials was evaluated by assessing their photocatalytic efficiency through the degradation of potassium butyl xanthate (PBX) under visible light. PBX is extensively used as a flotation agent in the mining industry, and its toxic nature poses a significant environmental pollution risk. Hence, it is crucial to develop efficient methods for degrading PBX. According to the findings, the optimized Fe3+-doped LZB photocatalyst demonstrated significantly better PBX degradation efficiency than pure LZB. Specifically, the optimized sample achieved a PBX degradation efficiency of 96.15% within 80 min under visible light, while pure LZB achieved only 32.17%. In addition, the optimized sample demonstrated a significantly higher rate constant of 0.0385 min−1 for the photodegradation of PBX, which was about 7.55 times faster compared to pure LZB. The observed improvement in photocatalytic performance was ascribed to the incorporation of iron ions at a suitable concentration, which not only augmented the absorption of visible light but also promoted the efficient separation of photogenerated charges. This study therefore represents a significant advancement in the development of effective photocatalytic techniques for the treatment of mineral processing wastewater.

Natural marmatite photocatalyst for treatment of mineral processing wastewater to help zero wastewater discharge

Mineral processing wastewater (MPW) with large discharge and high toxicity affects environmental safety, and the realizing zero discharge of MPW is of great significance for reducing environmental pollution, saving water resources, and promoting the sustainable development of the mining industry. In this study, we reported natural marmatite (NM) as a low-cost and efficient photocatalyst for the treatment of MPW to help zero wastewater discharge. The photocatalytic activity of NM was evaluated by the removal of total organic carbon (TOC) from MPW under visible-light illumination, and the optimal degradation conditions were discussed. Results showed that superoxide free radicals (·O2−) were the dominant active species responsible for organic pollutants degradation, and 74.25% TOC removal was obtained after 120 min reaction under the optimum treatment conditions. Meanwhile, the wastewater treated by NM photocatalysis can be reused in the flotation system without adverse impact on the product index. Based on these findings, a model of zero wastewater discharge for flotation with the help of photocatalytic treatment was established, it indicated that the water of the whole system can be balanced without affecting the ore dressing index, which showed that visible light-driven photocatalyst has a promising application prospect in the treatment and recycling of industrial wastewater.

Ag modified KNbO3/ g-C3N4 heterojunction for visible light degradation of flotation wastewater

With the wide application of flotation reagents, a large amount of wastewater containing flotation reagents enters natural water bodies and endangers human health. The commonly used treatment methods in sewage treatment plants are difficult to completely degrade flotation reagents in mineral processing wastewater. As a new advanced oxidation technology, photocatalytic oxidation has attracted attention in deep oxidation treatment of wastewater. In this study, a new Ag / KNbO3 / g-C3N4 ternanry composite potocatalyst was synthesized by hydrothermal method and photoreduction method, and characterized by various means.Among them, Ultraviolet-visible diffuse reflectance (UV-Vis DRS) studies showed that the formation of composite photocatalysts narrowed the band gap of g-C3N4 and effectively improved the performance of photocatalysts. X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and X-ray energy dispersive spectrometer (EDS) indicated that Ag was successfully doped and the photocatalyst had good purity. Through the scanning electron microscope (SEM-EDS MAPPING), silver nanoparticles are uniformly dispersed in the KNbO3 / g-C3N4 heterojunction structure as a bridge. The photocatalytic degradation experiment was carried out with the synthetic wastewater of ADD (Ammonium dibutyl dithiophosphate) as the target. It was confirmed that hydroxyl radicals (∙OH) and superoxide radical (∙O2−) were the main active substance for photocatalytic degradation of ADD, and the significant improvement of photocatalytic activity was mainly attributed to the local surface plasmon resonance effect (LSPR) of Ag.