Chromium-containing Wastewater Research Articles

Phytotoxicity of chromium-containing wastewater on germination and growth of Oryza sativa L

Leather tanning industries in Sukaregang area, Garut district-West Java, have been using chromium since 1980s. Since that time chromium containing wastewater has been polluting river water in the area since there has not been effective waste water treatment available until today. The polluted river water spread bad smell to the environment and the water also has been used by local farmers to irrigate their paddy field. This research was conducted to examine the effect of chromium containing wastewater to growth of paddy, including the physiology stress in plant organs. For examination of the effect of chromium to plant growth, Ciherang variety (Cvar) of paddy was grown in soil and treated with chemical solutions of K2Cr2O7 with concentrations of 50, 100, 200 mg/L, polluted river water (PRW) and distilled water as a control. Direct exposure of chromium 100-200 mg/L killed the plants a week after treatment. Exposure of the plant to wastewater and chromium 50 mg/L reduced plants growth. In Cr 50 mg/L treatment, chlorophyll content in paddy decreased to 60.82%, while the proline concentration in leaves increased by 18.47%. The activity of CAT and APX enzymes also increased, especially in paddy leaves after treated with Cr 50 mg/L, with the highest CAT activity value reached 1990.31 units/mg (an increase of 76.76%) and APX activity of 59.91 units/mg (an increase of 81.02%). The effect of chromium-containing wastewater to paddy was similar to the effect when the plant was exposed to 50 mg/L of chromium.

Photocatalytic Removal of Cr(VI) by Thiourea Modified Sodium Alginate/Biochar Composite Gel

Heavy metal pollution is an important problem in current water treatments. Traditional methods for treating chromium-containing wastewater have limitations such as having complicated processes and causing secondary pollution. Therefore, seeking efficient and fast processing methods is an important research topic at present. Photocatalysis is an efficient method to remove Cr(VI) from aqueous solutions; however, conventional photocatalysts suffer from a low metal absorption capacity, high investment cost, and slow desorption of trivalent chromium from the catalyst surface. In this study, a novel composite gel was synthesized by chemically modifying thiourea onto sodium alginate, which was then mixed with biochar. The composite gel (T-BSA) can effectively remove 99.98% of Cr(VI) in aqueous solution through synergistic adsorption and photocatalytic reduction under UV light irradiation. The removal mechanism of Cr(VI) was analyzed by FT-IR, FESEM, UV-DRS and XPS. The results show that under acidic conditions, the amino group introduced by chemical modification can be protonated to adsorb Cr(VI) through electrostatic interaction. In addition, the biochar as a functional material has a large specific surface area and pore structure, which can provide active sites for the adsorption of Cr(VI), while the photo-reduced Cr(III) is released into the solution through electrostatic repulsion, regenerating the adsorption sites, thereby improving the removal performance of Cr(VI). Biochar significantly intensifies the Cr(VI) removal performance by providing a porous structure and transferring electrons during photoreduction. This study demonstrates that polysaccharide-derived materials can serve as efficient photocatalysts for wastewater treatment.

Insights into Cr(VI) removal mechanism in water by facile one-step pyrolysis prepared coal gangue-biochar composite

The acceleration of industrialization has increased the discharge of chromium-containing wastewater, posing serious threat to the eco-environment and human health. To remove Cr(VI) in wastewater and improve resource utilization of solid waste, coal gangue and rape straw were initially used to prepare coal gangue-rape straw biochar (CG-RS) composite. The effects of pyrolysis temperatures, solution pH, coexisting ions of Cr(VI) adsorption were investigated. Different adsorption models combined with site energy analysis were used to explore the adsorption behaviors and mechanisms. The results showed higher pyrolysis temperature (600 °C) prepared CG-RS had a larger adsorption capacity (9.2 mg/g) for Cr(VI) (pH = 5.0). Analysis of XPS indicated that CG-RS successfully loaded with Fe–O and Al–O functional groups, which mainly participated in the reduction of Cr(VI). Site energy analysis further proved that reduction and surface complexation were the main adsorption mechanisms. This study shows an effective removal of Cr(VI) by CG-RS, providing a new way for resource utilization of solid waste.

Efficient Removal of Cr(VI) by TiO2 Based Micro-Nano Reactor via the Synergy of Adsorption and Photocatalysis.

The low-toxicity treatment of chromium-containing wastewater represents an important way of addressing key environmental problems. In this study, a core-shell structural ZIF-8@TiO2 photocatalyst was synthesized by a simple one-step hydrothermal method. The obtained composite photocatalyst possessed improved photocatalytic activity compared with TiO2. The results indicated that the optimized ZIF-8@TiO2 composite exhibited the highest removal efficiency with 93.1% of Cr(VI) after 120 min under UV-vis irradiation. The removal curves and XPS results indicated that the adsorbed Cr(VI) on the ZIF-8 during the dark process was preferentially reduced. The superior removal efficiency of ZIF-8@TiO2 is attributed to the combination of both high adsorption of ZIF-8, which attracted Cr(VI) on the composite surface, and the high separation efficiency of photo-induced electron-hole pairs. For the mixture of wastewater that contained methyl orange and Cr(VI), 97.1% of MO and 99.7% of Cr(VI) were removed after 5 min and 60 min light irradiation, respectively. The high removal efficiency of multiple pollutants provides promising applications in the field of Cr(VI) contaminated industrial wastewater treatment.

Dynamic experiment on the treatment of acidic chromium-containing wastewater by lignite loaded nano FeS.

In terms of the problem of severe pollution to the ecological environment caused by the acidic chrome-containing wastewater produced in the tanning, electroplating, metallurgy, printing and dyeing and other industries, based on the good adsorbability, reducibility and other properties of heavy metals such as Cr(vi) by lignite and nano FeS, the lignite-loaded nano FeS adsorbing material (nFeS-lignite) was prepared by ultrasonic precipitation method. NFeS-lignite and lignite were used as fillers to construct 1# and 2# dynamic columns to carry out the dynamic treatment experiment of acidic chrome-containing wastewater. And nFeS-lignite and lignite were characterized by XRD, SEM and EDS to explore the regularity, long-acting properties and removal mechanism of acidic chrome-containing wastewater treated by NFeS-lignite and lignite. The results indicate that: ① during 25 days of operation, the average removal percentages of Cr(vi) in the 1# and 2# dynamic columns are 71.6% and 53.1%. The average removal percentages of total chromium in 1# and 2# dynamic columns are 54.4% and 28.8%, and the average effluent pH of 1# and 2# dynamic columns is 5.3 and 7.3. ② According to XRD, SEM, EDS and FTIR analysis, the reducing groups in the structure of nFeS-lignite, such as –CH3, –CH2, C–O and Ar-OH, participate in the reaction and are oxidized to C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> C, CO and other groups. A large number of sediment crystals appeared on the particle surface, and new diffraction peaks such as FeOOH, Cr(OH)3 and Cr2S3 appeared at the same time, indicating that after Cr(vi) was reduced to Cr(iii), it would be fixed on the surface of nFeS-lignite in the form of precipitation such as hydroxide and sulfide.

Recycling and modeling of chromium from sludge produced from magnetic flocculation treatment of chromium-containing wastewater

In this paper, an effective and sustainable treatment method for recycling chromium from sludge produced by magnetic flocculation was established. Chromium was extracted from sludge with hydrogen peroxide and sodium hypochlorite, and then, superparamagnetic ferroferric oxide nanoparticles (MPs) were recovered by magnetic separation. The recovery percentage of chromium with sodium hypochlorite was higher than that with hydrogen peroxide, and the maximum was 99.12%. With increasing MPs use times, the adsorption percentage of chromium decreased, but there was no significant change in the recovery percentage of chromium in sludge. The purity of the recovered sodium chromate crystals was 96.28%. The back-propagation algorithm was used to model chromium recovery. The correlation coefficient between the model prediction data and experimental data was 0.9990, and the average absolute error was 0.51. The maximum recovery percentage of chromium obtained from model prediction was 99.27%, and the corresponding optimal conditions were consistent with those of experiments.

Self-regenerable bio-hybrid with biogenic ferrous sulfide nanoparticles for treating high-concentration chromium-containing wastewater

Biogenic ferrous sulfide nanoparticles (bio-FeS) as low-cost and green-synthesized nanomaterial are promising for heavy metals removal, but the need for complicated extraction, storage processes and the production of iron sludge still restrict their practical application. Here, a self-regenerable bio-hybrid consisting of bacterial cells and self-assembled bio-FeS was developed to efficiently remove chromium (Cr(VI)). A dense layer of bio-FeS was distributed on the cell surface and in the periplasmic space of Shewanella oneidensis MR-1, endowing the bacterium with good Cr(VI) tolerance and unusual activity for bio-FeS-mediated Cr(VI) reduction. An artificial transmembrane electron channel was constituted by the bio-FeS to facilitate extracellular electron pumping, enabling efficient regeneration of extracellular bio-FeS for continuous Cr(VI) reduction. The bio-hybrid maintained high activity within three consecutive treatment-regeneration cycles for treating both simulated Cr(VI)-containing wastewater (50 mg/L) and real electroplating wastewater. Importantly, its activity can be facilely and fully restored through bio-FeS re-synthesis or regeneration with replenished fresh bacteria. Overall, the bio-hybrid merges the self-regeneration ability of bacteria with high activity of bio-FeS , opening a promising new avenue for sustainable treatment of heavy metal- containing wastewater.

Design of BiOBr0.25I0.75 for synergy photoreduction Cr(VI) and capture Cr(III) over wide pH range

Conversion of hexavalent chromium (Cr(VI)) to trivalent chromium (Cr(III)) is an effective way to reduce its environmental risk, especially via photoreduction process. However, over a wide range of pH values, it is still a great challenge to achieve a high removal rate, and the disposal of produced Cr(III) should be concerned. In this work, we implemented a high removal rate at 98% for Cr(VI) and total chromium (Cr(T)) over a wide pH range (4–10) through the synergistic effect of adsorption, photoreduction and immobilization on the surface of BiOBr0.25I0.75. The substitution of bromine by iodine reduced the adsorption energy of Cr(VI) on BiOBr0.25I0.75, promoting the adsorption of Cr(VI). Meanwhile, the introduced iodine upshifted the conduction band (CB), enhancing the reduction ability for Cr(VI) to Cr(III). The negative surface of BiOBr0.25I0.75 can capture Cr(III), achieving a high removal rate for Cr(T). The pH-independent feature for Cr(VI) and Cr(III) removal make BiOBr0.25I0.75 a potential material for chromium-containing wastewater treatment. This work provides an effective strategy for removing chromium over a wide pH range.

Improvement of Technological Modes of Electrodialysis Apparatus for Treatment of Chromium-Containing Waste Waters

Improvement of Technological Modes of Electrodialysis Apparatus for Treatment of Chromium-Containing Waste Waters

Efficiency analysis of eggshell and tea waste as Low cost adsorbents for Cr removal from wastewater sample

This study aims to assess the efficiency of two agricultural wastes as adsorbents to remove Chromium (Cr) from a wastewater sample. Chromium-containing wastewater was treated with calcined and non-calcined eggshell and biochar tea waste with the adsorption method, and the effect of contact time, pH, and adsorbent dosage were investigated to examine the efficiency. The results indicate that 120 min is sufficient for the biochar tea waste and the non-calcined eggshell to reach adsorption equilibrium, where the calcined eggshell was reached equilibrium at 30 min. The optimal pH of all adsorbents was found to be 5, which indicates the interference of H+ ions on removing metal ions at low pH. Pseudo-first order and pseudo-second-order kinetic models were studied to assess the kinetic adsorption mechanism. Results also reveal that an increasing amount of adsorbent dose improves the removal efficiency of the adsorbent. The removal rates of using 2.0 g of non-calcined eggshell, 1.5 g of calcined eggshell and 2.5 g of biochar tea waste were found to be 70.70%, 100%, and 68.2%, respectively. The results show that the adsorption can be more appropriately described by the pseudo-second-order kinetic model for the adsorption of chromium ions from the wastewater. The findings of this study suggest that using these adsorbents, industrial wastewater can be treated in a more cost-effective and simple way than other existing methods.

Efficient treatment of wastewater from galvanic plants

The article discusses a promising method for the purification of chromium-containing wastewater from galvanic plants. A review and comparative analysis of existing methods and technologies for treatment of industrial waste from various organochromium compounds, such as reagent-based, biological, ion-exchange and others, are presented. The advantages of using the combined method of chromium-containing wastewater treatment based on electroflotation with preliminary electrocoagulation are shown. The effectiveness of the proposed combined method is evaluated and the design of electroflotocoagulator is developed.

Natural pyrite improved steel slag towards environmentally sustainable chromium reclamation from hexavalent chromium-containing wastewater

Currently, varied processes adopted to remove hexavalent chromium from aqueous solution have been realized to cause secondary pollution. As such, this study explored a green method for aqueous hexavalent chromium (Cr(Ⅵ)) reclamation by waste steel slag (SS) enhanced by natural pyrite (NP). Compared with the sole SS or NP, more efficient Cr(Ⅵ) removal was achieved by NP-SS at an initial pH value ranging from 1 to 8, resulting in a final pH value of 7–8. Cr(Ⅵ) in the solution could be initially reduced to Cr(III) by Fe2+ provided by NP, which was then bound with the OH- in the solution and the supersaturated calcium silicate hydrate on the surface of SS. In addition, the stearic acid anions existing on the surface of SS could promote the adsorption of Cr(III) to form chromium stearate. The used adsorbent could be potentially used for chromium smelting. Overall, this study provides a feasible and environmental sustainable solution to chromium reclamation from hexavalent chromium-containing wastewater.

Gold-silver nanoparticles modified electrochemical sensor array for simultaneous determination of chromium(III) and chromium(VI) in wastewater samples

The oxidation state of ions is a crucial aspect that often has been overlooked when determining the toxicity of chromium (Cr) species in environmental samples. In this study, a novel electrochemical sensor array based on gold-silver nanoparticles modified electrodes was developed for simultaneous determination of the two main chromium species (Cr(III) and (VI)). Specifically, the working electrodes of screen-printed carbon electrodes (SPCEs) were modified with silver-gold bimetallic nanoparticles through electrochemical deposition for detection of Cr(VI). The silver-gold bimetallic nanoparticles were further oxidized to form stable silver-gold bimetallic oxide nanoparticles for the detection of Cr(III). The results showed that the addition of silver with a theoretical value of 1% of gold could contribute to the formation and stabilization of oxides on the surface of gold nanoparticles. After characterization, the two kinds of electrodes were integrated as an electrochemical sensor array for selective and sensitive detection of Cr(VI) and Cr(III). The linear range and limit of detection (LOD, identified by three times of signal-to-noise ratio) were found to be 0.05–5 ppm and 0.1 ppb for Cr(VI), and 0.05–1 ppm and 0.1 ppb for Cr(III), respectively. Finally, the electrochemical sensor array was proven for successful detection of Cr(VI) and Cr(III) in tap water, artificial saliva and artificial sweat samples, and monitoring of Cr(VI) and Cr(III) in chromium-containing wastewater treatment process. Combined with a handheld dual-channel electrochemical device, the simultaneous determination of Cr(VI), Cr(III) and total chromium contents can be easily achieved for various samples.

Batch Electrocoagulation Process for Removal of Chromium from Tannery Wastewater

This study was aimed to investigate the chromium removal from the tannery wastewater through electrocoagulation. The zinc and copper plates were used as electrodes for the electrocoagulation process. The effectiveness of the electrocoagulation for chromium removal efficiency was examined investigating various parameters: applied voltage, time, and current density. In batch experiment, 500 mL chromium-containing wastewater was used for electrocoagulation. Chromium content in the raw wastewater and after treatment at optimized conditions was 340.1 and 6.9 mg/L, respectively. The efficiency of chromium removal and reduction of biochemical oxygen demand (BOD) was at 98.0 and 64.6%, accordingly. Although total dissolved solids (TDS) was slightly increased. The increment of current density enhances forming zinc hydroxide which causes the damage of electrodes. Electrocoagulation is an effective technique to remove chromium from the wastewater especially from the tannery wastewater.
 Journal of Engineering Science 12(1), 2021, 29-34

Review: Research Progress on Liquid–Liquid Extraction of Chromium

The wide application of chromium will definitely increase the probability of impact of chromium-containing effluents on the surrounding environment and human health. Prior to reviewing the research progress on the liquid–liquid extraction of chromium, the common methods for treating chromium-containing wastewater and chromium species in solution are first introduced. Liquid–liquid extraction processes of Cr(VI) and Cr(III) are respectively investigated in detail in subsequent sections. The typical oxidization effect of Cr(VI) and aging effect of Cr(III) are analyzed. Most of the mechanisms involved in chromium extraction processes are also reviewed. This literature review provides not only a theoretical basis for choosing an appropriate ion host, but also an important reference for optimization of chromium removal processes by solvent extraction. In the industrial production of nickel, cobalt, and scandium, it can also be used to predict the effects of Cr(III) aging and Cr(VI) oxidation on chromium-containing solvent extraction systems and further avoid these negative effects in advance.

The Crystallization Behavior and Stability of Chromite Synthesized in Chromium-Containing Wastewater at Room Temperature

The ferrite process can not only purify wastewater containing heavy metal ions but also recycle valuable metals from wastewater. Therefore, it is considered a promising technology to treat chromium-containing wastewater. However, the process has not been extensively applied in industry due to its high synthesis temperature. In this paper, the feasibility of chromite synthesis at room temperature was comprehensively studied. The effects of critical factors on the effluent quality and the crystallization behavior and stability of the synthetic products were investigated. Results showed that the removal ratio of chromium from wastewater was over 99.0%, and the chromium concentration in the supernatant reached the sewage discharge standard after undergoing the ferrite process at room temperature. Increases in the aeration rate, stirring rate, and reaction time were favorable for the formation of stable chromite. The particles obtained by the ferrite process at room temperature were characterized by a compact structure, and the maximum size of the particles reached 52 μm. Chromium gradually entered the spinel crystal structure during the synthesis process, and the molecular formula of the synthetic chromite might be Fe 3 − x Cr x O 4 , in which x was approximately 0.30. The path of the microscopic reaction was proposed to illuminate the synthesis mechanism of chromite under room temperature conditions. The present study has laid the foundation for the industrial application of the ferrite process in the purification and utilization of chromium-containing wastewater.

Research of the Purification Methods of Chrome-Containing Manufacturing Water

The article describes the most common current methods for treating industrial wastewater containing chromium compounds. Possible methods of recycling chromium-containing waste and difficulties associated with this process are identified, as well as increasing factors are noted. Concepts of electrocoagulation and reagent methods are presented, their advantages and disadvantages are noted. A process scheme for treatment of contaminated effluents of industrial enterprises is proposed, which provides for their release into the city drainage network. An example of a successful existing technology for recycling chromium-containing waste water is given. The most effective integrated method of treating industrial effluents is justified for industrial enterprises that have chromium-containing wastewater. It provides for the combination of the electrocoagulation method with the post-treatment of wastewater by the reagent method. As reagents, it was proposed to use barium chloride 2-aqueous and iron sulphate (II) 7-aqueous (iron sulfate). Comparative calculation of the required amount of reagents and its cost was made.

Bi2S3 Nanowires: First-Principles Phonon Dynamics and Their Photocatalytic Environmental Remediation

We reported the synthesis and full characterization of ultralong Bi2S3 nanowires with diameters of 60–80 nm and lengths above 1 μm, showing growth in the [001] direction. Combining the computed lattice dynamics of orthorhombic Bi2S3 with the experimental micro-Raman scattering study provided comprehensive solutions. We demonstrate that 10 active modes originated from Raman symmetry modes (4Ag + 2B1g + 3B2g + 1B3g), and the peak at 124 cm–1 is due to the IR-active B3u mode. The use of the Bi2S3 catalyst for dewatering hexavalent chromium-containing wastewater was also reported. This confirms it to be a potential candidate for photocatalytic environmental remediation.

A novel approach to Chromium rejection from sewage wastewater by pervaporation

Pervaporation is an effective method, especially in the separation of azeotropic mixtures or in the recovery of some components from the mixtures. Although various methods have been used for the treatment of chromium-containing wastewater that has become a matter of concern for the health of aquatic ecosystems, the pervaporation has never been used before in the literature. In this study, Cr/water (Cr (III), Cr (VI)) mixtures were separated by a pervaporation using polyvinyl alcohol (PVA) and sodium Y (NaY) zeolite membranes. Study results indicated that increasing the zeolite percentage, the membrane thickness, the amount of Cr in the feed solution and, the pH all increased rejection and decreased flux. In contrast, an increase in temperature caused rejection to decrease and flux to increase. The best rejection obtained for Cr (VI) was 144.4%. For Cr (VI) removal from sewage wastewater, the maximum rejection under optimum conditions was 160% and the flux was 0.12 kg/m2h. Also, Cr (VI) was not detected in any permeates. The permeate concentration was calculated to be 97.1% in experiments with a Cr (III)/water mixture. PVA/NaY membrane showed selective permeability for Cr (VI), while it does not show selective permeability for the useful Cr (III) component.

Fe3O4@Mesoporous-SiO2@Chitosan@Polyaniline Core–Shell Nanoparticles as Recyclable Adsorbents and Reductants for Hexavalent Chromium

In this work, we designed the Fe3O4@mesoporous-SiO2@chitosan@polyaniline core–shell nanoparticles (Fe3O4@mSiO2@CS@PANI, hence abbr. FSCP), which can be used to capture Cr(VI) in wastewater. Rapid adsorption behavior and high removal capability (249.6 mg Cr(VI) per gram of FSCP) were exhibited by this material. X-ray photoelectron spectroscopy (XPS) analysis demonstrates that Cr(VI) was adsorbed and in situ reduced on FSCP at pH 2. Adsorption was facilitated by the electrostatic attraction of HCrO4– and −N+═C–/–N+H–, while the active −NH–/–N+H– sparked the reduction of Cr(VI) to Cr(III). Moreover, the coordination of the resulting Cr(III) with the amino group promoted adsorption, thus achieving detoxification of Cr(VI) in wastewater. After eight recycling experiments, the Cr(VI) removal efficiency of this material is still more than 90%, indicating that this material has excellent stability and good application potential. Therefore, this magnetic adsorbent offers a potential solution for the successful handling of chromium-containing wastewater.