Phytoextraction of Cr(VI) from soil using Portulaca oleracea

Cr(VI) represents an environmental challenge in both soil and water as it is soluble and bioavailable over a wide range of pH. In previous investigations, Portulaca oleracea (a plant local to the United Arab Emirates (UAE)) demonstrated particular ability for the phytoextraction of Cr(VI) from calcareous soil of the UAE. In this publication, the results of the evaluation of P. oleracea phytoextraction of Cr(VI) from UAE soil at higher concentrations are reported. P. oleracea was exposed to nine different concentrations of Cr(VI) in soil from 0 to 400 mg kg^?1. The uptake of Cr(VI) increased as its concentration in soil increased between 50 and 400 mg kg^?1, with the most efficient removal in the range from 150 to 200 mg kg^?1. The total chromium concentrations exceeded 4600 mg kg^?1 in roots and 1400 mg kg^?1 in stems, confirming the role of P. oleracea as an effective Cr(VI) accumulator. More than 95% of the accumulated Cr(VI) was reduced to the less toxic Cr(III) within the plant.     

Statistical interpolation model for the description of ground pollution due to the TCDD produced in the 1976 chemical accident at seveso in the heavily contaminated zone “A”;

The influence of NTA on chromium genetic activity was studied in the D7 strain of Saccharomyces cerevisiae. At low dose (subgenotoxic) of sodium chromate (CrVI) (5mM), NTA increased the point mutation while at higher dose (25 mM) of chromate in the presence of NTA a decrease of point reverse mutation was observed. Probably NTA affected either the uptake of Cr(VI) favouring the intracellular reduction to Cr(III), or the recombinational repair of DNA breaks induced by chromate oxiding activity.

An increase of point (reverse) mutation was obtained in the experiments with NTA and chromium chloride, suggesting the hypothesis that NTA might interact with Cr(III) forming NTA‐Cr(III) complexes able to permeate cellular membranes and bind to DNA. In addition NTA genetic inactivity was confirmed.     

Effects of Cr(III) organic compounds on Lactobacillus plantarum

Biotransformation of Cr(VI) to less toxic Cr(III) has been known to produce insoluble Cr(III) compounds and soluble Cr(III) organic complexes. However, recent research reports have indicated that Cr(III) organic complexes are relatively stable in the environment. Little has been reported on the fate and toxic effects of Cr(III) organic compounds on organisms. In this study, the toxic effects of the soluble Cr(III) organic complexes [Cr(III) citrate, Cr(III) histidine, Cr(III) lactate and Cr(III) glutamate] to a local strain of Lactobacillus plantarum isolated from sauerkraut was investigated. Growth inhibition, viable cell count and lactic acid inhibition were measured to determine the toxicity potential of the test compounds. The EC₅₀ values of Cr(III) citrate, Cr(III) histidine, Cr(III) lactate, and Cr(III) glutamate, calculated from the percent growth inhibition were found to be 56 mg L^?1, 70 mg L^?1, 81 mg L^?1, and 85 mg L^?1, respectively. Similar trend was observed in the viable cell counts and lactic acid production. Cr(VI) was observed to be more toxic than the Cr(III) organic compounds, while inorganic Cr(III) was the least toxic. The severity seemed to increase with increase in chromium compounds’ concentration. The results showed that Cr(III) citrate was the most toxic Cr(III) organic compound, while Cr(III) glutamate was the least.     

Biochemical speciation in chromium genotoxicity

The biochemical speciation of chromium compounds in mammalian cells is discussed with respect to uptake, metabolism, DNA binding and damaging. Whereas soluble hexavalent chromium is taken up rapidly and accumulated intracellularly after its reduction, compounds of trivalent chromium penetrate biomembranes about three orders of magnitude slower. Cr(VI) after its uptake is metabolised by electron donating compounds via Cr(V) to Cr(III) compounds. Chromium from various Cr(III) compounds, but not chromate, binds to chromatin in isolated cell nuclei. The DNA‐protein crosslinks and DNA strand breaks observed in rat liver and kidney after chromate administration are also found in vitro, when Cr(III) compounds (but not chromate) interacts with isolated nuclei. In the Chinese Hamster cell HGPRT mutation assay, three out of four tested Cr(III) complexes were found to be mutagenic. In a direct DNA strand break assay with supercoiled bacteriophage PM 2 DNA, neither chromate nor the four Cr(III) compounds tested caused nicks. However, the combined action of chromate plus glutathione as well as the isolated complex of pentavalent chromium, Na₄Cr(glutathione)₄, did cause DNA breaks. Reactive oxygen species are inferred to be the ultimate DNA nicking agents in this assay. In conclusion there appear to be two mechanisms of chromate genotoxicity; one with direct DNA damage caused by Cr(V) species and one via DNA‐protein crosslinks formed with Cr(III), the final reduction state of chromate.     

Removal of chromium(VI) by ZnCl2 activated coir pith carbon

The adsorption of chromium(VI) onto ZnCl₂ activated carbon developed from coir pith was investigated to assess the possible use of this adsorbent. The influence of contact time, adsorbent dose, Cr(VI) concentration, pH and temperature were investigated. The two theoretical adsorption isotherms, namely, Langmuir and Freundlich were used to describe the experimental results. The Langmuir adsorption capacity (Q ₀) was found to be 120.5?mg Cr(VI) per g of the adsorbent. The adsorption followed the second-order kinetics and was found to be maximum at pH 2.0. The pH effect and the desorption studies showed that ion exchange mechanism might be involved in the adsorption process. The effects of foreign ions such as chloride, sulphate, phosphate, selenite, molybdate, nitrate and perchlorate on the removal of Cr(VI) have been investigated. The removal of Cr(VI) from synthetic ground water was also tested. The results show that ZnCl₂ activated coir pith carbon is effective for the removal of Cr(VI) from water.     

Role of the vitamin E model compound Trolox in the prevention of Cr(VI)-induced cellular damage

Given the wide industrial use of chromium (Cr) and its environmental contamination, chromium represents a risk to humans exposed to the metal. Considering that Cr(VI) is a potent oxidizing agent that increases intracellular oxidation and DNA damage, it would be worth considering the pretreatment of cells with antioxidants as a means of preventing Cr(VI)-induced toxicity. The objective of this study was to pretreat yeast cells with the water-soluble vitamin E analogue Trolox in an effort to increase cell tolerance against reactive chromium and reactive oxygen species formed during Cr(VI) reduction. Results revealed a decrease in Cr(VI)-induced cytotoxicity and mitotic gene conversions in Trolox-pretreated cells. The protective effect of Trolox in Cr(VI) induced genotoxicity was confirmed also with the prokaryotic Salmonella typhimurium SOS/umu test. Pretreatment of cells with Trolox (1) increased total Cr bioaccumulation, (2) decreased Cr(VI)-induced intracellular oxidation, (3) decreased Cr(V) persistence and (4) increased OH^? formation in yeast extracts. These findings might be useful in directing future investigations concerning the use of Trolox as a human antioxidant supplement, and in clinical applications related to Cr-induced genotoxicity in occupational and environmental situations where chromium is a problem.     

Role of NADH-dependent chromium reductases,exopolysaccharides and antioxidants by Paenibacillus thiaminolyticus PS 5 against damage induced by reactive oxygen species

ABSTRACT

Cr (VI) being used in various activities of industries and its improper treatment lead to contamination of environment. Among different methods, biological is the most efficient method to control pollution from soils affected with metals. Present study was designed to assess the role of Paenibacillus thiaminolyticus PS5 for adsorption, Cr (VI) reduction and mechanism of reduction. Sorption of chromium (VI) by strain PS5 was obtained by batch equilibrium method. Cr (VI) reduction in both free and immobilised cells were evaluated by 1,5-Diphenyl Carbazide method. The formation of biofilm by Paenibacillus thiaminolyticus PS5 was observed for colour change as well as quantified spectrophotometrically. Analysis kits were used to measure the amount of eDNA, superoxide and malondialdehyde (MDA). Metal resistant strain PS5 was characterised as P. thiaminolyticus using 16S rRNA gene sequence. Maximum biosorption of Cr (VI) by strain PS5 was found at pH 6–8 and 100–400 µgCr/mL within 24 hours of incubation. Complete reduction of Cr (VI) by strain PS5 was achieved at pH 6–8 and100–300 µg/mL Cr (VI). Paenibacillus thiaminolyticus PS5 immmobilisation on sodium alginate and polyvinyl alcohol facilitated complete reduction of Cr (VI) within 18 hours due to the formation of more biofilm under metal stress conditions. Strain PS5 reduced almost all Cr (VI) into Cr (III) in supernatant, most of which was immobilised by cell debris. Experiments confirmed the reduction of Cr (VI) by cytosolic cell-free extracts which is a mechanism of detoxification. The release of exopolysaccharides and antioxidants by strain PS5 played a protective role against cell damage by Cr (VI) as Cr (VI) could not release the significant amount of eDNA, superoxide and MDA. The present study proved strain PS5 to be a super bioinoculant which has great capacity for adsorption, biotransformation and can activate cytosolic reductases, exopolysaccharides and antioxidants against oxidative damage.     

Enhancement of UV and chromate mutagenesis by nickel ions in the Chinese hamster HGPRT Assay †

1. The HGPRT (Hypoxanthine‐Guanine‐Phospho‐Ribosyl‐Transferase) assay with Chinese Hamster V79 cells was used to measure the mutagenic effects of UV irradiation, potassium dichromate and nickel chloride. The agents were tested separately and in the combinations of UV plus nickel and dichromate plus nickel.

2. UV, Cr(VI) and Ni(II) were confirmed to be mutagenic in the V79 cell assay. The combination of UV(5J/m²) and Ni(II) (0.5 mM) caused a mutation rate 11.2 times above that corresponding to the sum of the individual mutation rates of these agents. The combined action of Cr(VI) (0.1 mM) and Ni(II) (0.5 mM) produced a mutation rate 2.8 fold above that corresponding to the sum of the individual rates of the separate agents.

3. The enhancing effect of nickel chloride on the mutagenicity of UV or Cr(VI) is interpreted by an interference of Ni(II) with the repair of DNA lesions.     

Removal of Cr(VI) from aqueous solutions by the culm of bamboo grass treated with concentrated sulfuric acid

We prepared a carbonaceous sorbent for Cr(VI) from the culm of Sasa kurilensis by dehydration with concentrated H₂SO₄. The removal of Cr(VI) by the sorbent was highly solution pH dependent and mainly governed by physicochemical sorption. The equilibrium data fit well in the Langmuir isotherm model and indicate the endothermic nature of the Cr(VI) sorption. The desorption experiments suggest that the Cr(VI) sorption is generally irreversible, owing to strong interaction of HCrO₄⁻ with the active sites of the sorbent.     

Bioreduction of hexavalent chromium by Exiguobacterium indicum strain MW1 isolated from marine water of Paradip Port,Odisha, India

Hexavalent chromium-tolerant (1500?mg/L) bacterium MW1 was isolated from harbour water of Paradip Port and evaluated for Cr(VI) reduction potential. The isolate was identified as Exiguobacterium indicum by biochemical and 16S rRNA gene sequence methods. Salt tolerance of the bacterium was evaluated in a wide range of NaCl concentrations (0.5–13%, w/v). The Cr(VI) reduction of the strain was evaluated and optimised with varied Cr(VI) concentrations (100–1000?mg/L), pH (5.0–9.0), temperature (30–40°C) and shaking velocity (100–150?rpm) in two different minimal media (M9 and Acetate). Under optimised conditions, after 192?h of incubation nearly 92%, 50% and 46% reduction in the M9 minimal medium and 91%, 47% and 40% reduction in the acetate minimal medium were observed for 100, 500 and 1000?mg/L of Cr(VI), respectively. The exponential rate equation for Cr(VI) reduction yielded higher rate constant value, that is, 1.27?×?10^?2?h^?1 (M9) and 1.17?×?10^?2?h^?1 (Acetate) in case of 100?mg/L and became lower for 500 and 1000?mg/L Cr(VI) concentrations. Further, the association of bacterial cells with reduced product was ascertained by Fourier transform infrared spectrometer, UV–Vis–DRS and field-emission scanning electron microscope–energy-dispersive X-ray analyses. The above study suggests that the higher reducing ability of the marine bacterium E. indicum MW1 will be suitable for Cr(VI) reduction from saline effluents.     

Response of indigenous Cd-tolerant electrochemically active bacteria in MECs toward exotic Cr(VI) based on the sensing of fluorescence probes

Electrochemically active bacteria (EAB) on the cathodes of microbial electrolysis cells (MECs) can remove metals from the catholyte, but the response of these indigenous EAB toward exotic metals has not been examined, particularly from the perspective of the co-presence of Cd(II) and Cr(VI) in a wastewater. Four known indigenous Cd-tolerant EAB of Ochrobactrum sp X1, Pseudomonas sp X3, Pseudomonas delhiensis X5, and Ochrobactrum anthropi X7 removed more Cd(II) and less Cr(VI) in the simultaneous presence of Cd(II) and Cr(VI), compared to the controls with individual Cd(II) or single Cr(VI). Response of these EAB toward exotic Cr(VI) was related to the associated subcellular metal distribution based on the sensing of fluorescence probes. EAB cell membrane harbored more cadmium than chromium and cytoplasm located more chromium than cadmium, among which the imaging of intracelluler Cr(III) ions increased over time, contrary to the decreased trend for Cd(II) ions. Compared to the controls with single Cd(II), exotic Cr(VI) decreased the imaging of Cd(II) ions in the EAB at an initial 2 h and negligibly affected thereafter. However, Cd(II) diminished the imaging of Cr (III) ions in the EAB over time, compared to the controls with individual Cr(VI). Current accelerated the harboring of cadmium at an initial 2 h and directed the accumulation of chromium in EAB over time. This study provides a viable approach for simultaneously quantitatively imaging Cd(II) and Cr (III) ions in EAB and thus gives valuable insights into the response of indigenous Cd-tolerant EAB toward exotic Cr(VI) in MECs.

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胶原纤维固化黑荆树单宁吸附Cr(VI)的研究

研究了胶原纤维固化黑荆树单宁对Cr(VI)的吸附.采用不同温度、pH值等条件进行吸附研究,并进一步探讨了固化黑荆树单宁的吸附动力学和吸附柱动力学及其吸附机理.结果表明,该材料对Cr(VI)的吸附平衡符合Freundlich方程,温度对吸附平衡的影响不明显;吸附动力学可用拟二级速度方程来描述,该材料同时具有良好的柱动力学特性;Cr(VI)的吸附过程可能存在3个反应,即Cr(VI)与吸附剂之间发生氧化还原反应生成Cr(III),Cr(III)和-COOH之间发生离子交换反应,以及Cr(III)与单宁的邻位羟基发生螯合.图8表2参10     

Biosorption of Cr(VI) from wastewater using Sorghastrum Nutans L. Nash

Sorghastrum Nutans L. Nash is used as an adsorbent for the removal of Cr(VI) from wastewater. Adsorption coupled reduction i.e. indirect reduction is the mechanism of Cr(VI) removal by the biomaterial. The adsorbent surface became highly positively charged at lower pH, adsorption rate of Cr(VI) is faster and reduction reaction also accelerates at lower pH since the binding of negatively charged Cr(VI) ion species to the cationic groups is enhanced and protons take part in this reaction. The adsorbent is characterised by using XRD, FTIR, SEM and EDAX analysis. OH bending, CN stretching/bending and NH stretching play a major role in Chromium adsorption. Experimental values follow pseudo-second order reaction and Langmuir adsorption isotherm. Surface diffusion is the rate controlling mechanism for the process. The maximum percentage of Cr(VI) removal obtained is 75.5% with 7?g/L dosage at pH 1.3 and adsorbate concentration was 100?mg/L. From the normal probability, residual, contour, 3D surface, main effect and interaction plot along with t-test, ANOVA, and F-test, it is observed that pH has the most significant effect on the percentage removal followed by adsorbent dosage and time. The adsorbate concentration has the least effects and interaction effects are found to be significant.     

Fluorescence studies of dye displacement from DNA by chromium(III) complexes: Evidence for cation induced DNA condensations

The interactions of 10 different chromium(III) complexes with isolated calf thymus DNA have been analysed by studying the electronic and fluoresence spectra of intercalated ethidiumbromide. Triply charged cationic complexes including: [Cr(urea)₆]Cl₃.3H₂O, [Cr(1,10‐phenanthroline)₃](ClO₄)₃.2H₂O, [Cr(2,2'‐bipyridyl)₃] (ClO₄)₃.2H₂O, [Cr(ethylendiamine)₃]Cl₃.3.5H₂O and [Cr(NH₃)₆](NO₃)₃ displaced the dye from DNA. Similar effects were observed in experiments using the non‐intercalating dye bisbenzimidazole ("Hoechst 33258"). However, singly charged cationic, anionic and uncharged chromium(III) complexes such as: cis‐[Cr(1,10‐phenanthroline)₂Cl₂]Cl.2H₂O, cis‐[Cr(2,2'‐bipyridyl)₂Cl₂]Cl.2H₂O, [Cr(glutathione)₂]Na₂, [Cr(cysteine)₂]Na.2H₂O and [Cr(glycine)₃] were unable to displace both ethidiumbromide and bisbenzimidazole from DNA. There was no evidence for the formation of co‐ordinate bonds between chromium(III) and DNA for any of the above complexes. The charge and type of ligand are important in controlling the interaction of chromium(III) with isolated DNA in vitro. Our findings indicate that the outer sphere interaction of a chromium(III) complex with DNA is weak and unlikely to be the mechanism by which chromate causes DNA impairments in vivo and in vitro.     

Bioavailability and metabolism of hexavalent chromium compounds †

Intratracheal instillation of ⁵¹CrCl₃ in anaesthetized rabbits resulted in partial absorption. In blood, the absorbed material was entirely confined to the plasma compartment. Only trace amounts were deposited in liver and kidney. By contrast, after similar application of Na, ⁵¹CrO₄ the bulk of blood radioactivity was present in red blood cells (RBC). Substantial deposition occurred in liver and kidneys. It is concluded that Cr(VI) may enter the body unreduced via the lung and is partially deposited in cells over a prolonged period of time.

Since chromium was accumulated in liver after administration of Cr(VI) we investigated the intracellular disposition of Cr(VI) in the isolated perfused liver. No significant sex differences in chromium distribution were observed. At the end of the experiments (1 h), 60% of the applied dose (312μg Cr/liver) was located in the cytosol, whilst 14% was in the mitochondria, 9% in the microsomal pellet and 2% was associated with the nuclei. Gel chromatography of the cytosolic compartment showed that the overwhelming part of chromium was eluted in fractions with an apparent molecular weight of 6,000 dalton. These fractions exhibited absorption maxima at 410nm and 548nm. It is concluded, that cytosolic reduction might be the main intracellular redox pathway for chromates. This view was confirmed by monitoring the reaction of Cr(VI) with GSH in vitro. GSH reduced Cr(VI) without further cofactors under formation of GSH‐chromium complexes, which possibly represent major intermediates in the metabolism of Cr(VI).     

Microbiological reduction of hexavalent chromium by indigenous chromium-resistant bacteria in sand column experiments

Indigenous bacteria that are resistant to high concentrations of Cr(VI) were isolated from a Cr-contaminated sediment. Sand column experiments were conducted using the isolated bacteria to investigate microbial effects on Cr(VI) reduction in open systems that simulated subsurface conditions. The indigenous Cr-resistant bacteria appeared to reduce Cr(VI) in the column experiments. When 12 mg/L of Cr(VI) was injected into the columns, the removal efficiencies of Cr(VI) by the isolated bacteria were 39.1%, 62.5%, and 63.6% at 24, 48, and 72 h retention times of Cr(VI) solution, respectively. These results imply that the linear velocity of groundwater or pore water should be less than 0.63 cm/h for effective removal of Cr(VI) in subsurface conditions. In comparison, the noninoculated control column did not show a significant variation in dissolved Cr(VI) concentration. The results indicated that reduction of Cr(VI) was occurring in the column due to the activity of the indigenous bacteria.     

Selective separation and preconcentration studies of chromium(VI) with Alamine 336 supported liquid membrane

Chromium compounds have received considerable attention because these are used extensively in such industrial applications as electroplating, steelmaking, tanning of leather goods, and corrosion inhibition. The use of supported liquid membranes (SLMs) to remove metals from wastewaters has actively been pursued by the scientific and industrial community. In the present work, the selective separation and preconcentration of Cr(VI) ions has been studied by using a commercial amine as the membrane liquid on the porous polypropylene support. Permeation experiments were conducted on a laboratory scale batch reactor made up of perspex, with a memberane fixed amid the two chambers. The flux of Cr(VI) ions was found to be maximum (3.15?×?10^?5?mol?cm^?2?s^?1) around pH 1. Above and below this pH the flux decreases. Distribution studies show that an increase in the amine concentration leads to higher distribution coefficients at fixed pH values. At pH around unity, the distribution of Cr(VI) ions into the organic phase was found to be maximum, of the order of 56.3. The Cr(VI) transport through the membrane increases with rise in temperature. In order to check the long-term efficiency of the flat sheet SLM, an experiment was conducted with higher Cr(VI) concentration (5000?ppm) for 24?h, at optimised parameters. It was observed that in 24?h, about 1/5th of the feed Cr(VI) is left over while the rest is transported. However, minute organic droplets were also seen in the feed and strip compartments, after 1 day. This observation suggested the loss of membrane liquid. The feasibility of preconcentration of Cr(VI) by using the proposed SLM parameters, was also studied by using the hollow fibre (HF) system. Highest enrichment factor (E.F) value was obtained for 50?mg?L^?1 whereby all of the metal was transported to the stripping phase and the resulting Cr concentration was 688?mg?L^?1 (E.F?=?13.8). It was observed that while treating more diluted solutions, the enrichment factor decreases. The values of E.F equal to 8.9 and 11.3 were found for initial Cr concentration of 10 and 30?mg?L^?1.     

Analyses of PAHs (polycyclic aromatic hydrocarbons) and mutagenicity in raw and chlorinated water

Both raw water and chlorinated drinking water samples were collected from and the Liu‐Du water treatment plant in northern Taiwan from October 1990 to April 1992. The polycyclic aromatic hydrocarbons (PAHs) and mutagenicity in these water samples were analyzed by GC/MS and Ames test. The Mutagenicity/DMSO (Dimethyl Sulfoxide) ratio in S. typhimurium TA98 and TA100 with or without S9 mixture increased, even higher than 2, following the sequence of unit process. It was observed that the mutagenicity with TA98 (S9+) was highly related to most of PAHs in the raw water; while the mutagenicity with TA98 (S9+) was only correlated with DbA and BghiPr in the treated water. It could be expected that the mutagenicity level was controlled by other predominant components after the raw water was treated, for example, the chlorination process.     

Enhancement of extracellular Cr(VI) reduction for anammox recovery using hydrazine: performance,pathways, and mechanism

● N₂H₄ addition enhanced and recovered anammox performance under Cr(VI) stress. ● N₂H₄ accelerated electron transfer of Cr(VI) reduction for detoxification. ● N₂H₄ enhanced anammox metabolism for activity recovery from Cr(VI) inhibition. ● Extracellular Cr(VI) reduction to less toxic Cr(III) was the dominant mechanism. The hexavalent chromium (Cr(VI)) would frequently impose inhibition to anaerobic ammonium oxidation (anammox) process, hindering the efficiency of nitrogen removal in wastewater treatment. Hydrazine (N₂H₄), which is an intermediate product of anammox, participates in intracellular metabolism and extracellular Cr(VI) reduction. However, the roles of N₂H₄-induced intracellular metabolism and extracellular reduction in nitrogen removal under Cr(VI) stress remain unclear. The addition of 3.67 mg/L of N₂H₄ increased the anammox activity by 17%. As an intermediate, N₂H₄ enhanced anammox metabolism by increasing the heme c content and electron transfer system activity. As a reductant, N₂H₄ accelerated the reduction of c-Cyts-mediated extracellular Cr(VI) to the less toxic Cr(III). Extracellular Cr(III) accounts for 74% of the total Cr in a Cr(VI)-stressed anammox consortia. These findings highlight that N₂H₄-induced extracellular Cr(VI) reduction is the dominant mechanism for the survival of anammox consortia. We also found that N₂H₄ increased the production of extracellular polymeric substances to sequester excessive Cr(VI) and produced Cr(III). Taken together, the study findings suggest a potential strategy for enhancing nitrogen removal from ammonium-rich wastewater contaminated with Cr(VI).     

Fabrication of highly efficient Bi2WO6/CuS composite for visible-light photocatalytic removal of organic pollutants and Cr(VI) from wastewater

• A novel Bi₂WO₆/CuS composite was fabricated by a facile solvothermal method. • This composite efficiently removed organic pollutants and Cr(VI) by photocatalysis. • The DOM could promoted synchronous removal of organic pollutants and Cr(VI). • This composite could be applied at a wide pH range in photocatalytic reactions. • Possible photocatalytic mechanisms of organic pollutants and Cr(VI) were proposed. A visible-light-driven Bi₂WO₆/CuS p-n heterojunction was fabricated using an easy solvothermal method. The Bi₂WO₆/CuS exhibited high photocatalytic activity in a mixed system containing rhodamine B (RhB), tetracycline hydrochloride (TCH), and Cr (VI) under natural conditions. Approximately 98.8% of the RhB (10 mg/L), 87.6% of the TCH (10 mg/L) and 95.1% of the Cr(VI) (15 mg/L) were simultaneously removed from a mixed solution within 105 min. The removal efficiencies of TCH and Cr(VI) increased by 12.9% and 20.4%, respectively, in the mixed solution, compared with the single solutions. This is mainly ascribed to the simultaneous consumption electrons and holes, which increases the amount of excited electrons/holes and enhances the separation efficiency of photogenerated electrons and holes. Bi₂WO₆/CuS can be applied over a wide pH range (2–6) with strong photocatalytic activity for RhB, TCH and Cr(VI). Coexisiting dissolved organic matter in the solution significantly promoted the removal of TCH (from 74.7% to 87.2%) and Cr(VI) (from 75.7% to 99.9%) because it accelerated the separation of electrons and holes by consuming holes as an electron acceptor. Removal mechanisms of RhB, TCH, and Cr(VI) were proposed, Bi₂WO₆/CuS was formed into a p-n heterojunction to efficiently separate and transfer photoelectrons and holes so as to drive photocatalytic reactions. Specifically, when reducing pollutants (e.g., TCH) and oxidizing pollutants (e.g., Cr(VI)) coexist in wastewater, the p-n heterojunction in Bi₂WO₆/CuS acts as a “bridge” to shorten the electron transport and thus simultaneously increase the removal efficiencies of both types of pollutants.