Chromium In Wastewater Research Articles

A Miniature Biosensor Based on Microbial Fuel Cell for Hexavalent Chromium in Wastewater

Hexavalent chromium is considered as a human carcinogen due to its mutagenic and teratogenic properties, which can cause severe birth defects. Microbial Fuel Cell (MFC) is a promising power generation device for sustainable energy. The application of MFC is limited due to low power generation. In the present study, a miniature biosensor based on microbial fuel cell has been designed and assembled for detecting hexavalent chromium in wastewater. The miniature biosensor can generate power for sustaining operation. The power provided by the biosensor has been studied in the present investigation. Besides, both conductive silver glue and carbon cloth are employed as the anode for the biosensor. Electrochemical analyses for the above materials are conducted for the biosensor in detecting hexavalent chromium in the anode chamber. It is found that the maximum voltage can reach up to 518.17 mV and the power density of 1,075 mW/cm2 can be achieved with carbon cloth as the anode electrode using an external resistance of 1000W. It is also measured that a higher limiting current density can reach up to 0.015 mA/cm2 with conductive silver glue as the anode electrode. Furthermore, the voltage output of the biosensor decreased severely with the addition of hexavalent chromium into the wastewater. In addition, the recovery time for the biosensor is much shorter than those in previous studies. It is concluded that the biosensor possesses the potential of simultaneous detection of hexavalent chromium and electricity generation, leading to a new era of autosensing applications in the environment as well as smart powering devices.

Efficient detection and degradation of hexavalent chromium wastewater in tourist attractions using dual-fluorescent UiO-66-NH2 stabilized polysulfone Pickering emulsions

This investigation delineates the synthesis of a novel, bifunctional composite material, embedding cadmium telluride (CdTe) and carbon quantum dots (CQDs) within the metal-organic framework UiO-66-NH2, fabricated through a Pickering emulsion technique to augment the photocatalytic degradation and detection of hexavalent chromium (Cr(VI)). We elucidate that the integration of these quantum dots substantially narrows the bandgap energy of UiO-66-NH2 to 1.76 eV for CQDs and 2.83 eV for the composite, thereby enhancing the spectrum of visible light absorption and fortifying charge carrier separation. The foundlings reveal a pronounced elevation in photocatalytic performance, with the composite material accomplishing up to 90 % reduction of Cr(VI) within 200 min under visible light exposure. Moreover, the composite demonstrates robust reusability, sustaining efficacious degradation across numerous cycles with minimal attenuation in activity. The composite material can detect and degrade Cr(VI) in the environment, providing an efficient means of heavy metal pollution remediation for tourist attractions. It is economical and sustainable, aligning with the green and low-carbon tourism development concept.

Environmental performance of three innovative leather production processes using less chromium and water

Leather production contributes positively to economic developments but can create severe environmental impacts, due to the associated consumptions of water and chemicals. The substance of main concern is the basic chromium sulphate, widely used as tanning agent, which provides high-technical performance to the finished leather. This study quantifies the environmental sustainability of a conventional leather production process and those of three innovative processes, characterised by limited consumptions of chromium and water. Standardised life cycle assessments were implemented, with reference to the production chains starting from pickled skins until the production of two finished leathers (for goods and footwear), having the same technical and aesthetic characteristics of those from the conventional process. The innovative tanning processes adopt conventional rotating drums or substitute them with spray nozzles or aerosol rooms, and require a specific pre-treatment that includes de-pickling, drying and stabilisation of input skins. Tests at industrial scale (or at pilot scale for the solution with aerosol rooms) indicate that the new processes strongly reduce impacts in terms of Human toxicity-cancer, Ecotoxicity freshwater and Resource use-minerals and metals (up to 57 %, 29 % and 48 %, respectively) even though they imply an increase in terms of Climate Change (up to 51 %). Losses of chromium in wastewater and solid waste are reduced from >33 g/m2finished leather, for the conventional process, to about 8 g/m2finished leather, 5 g/m2finished leather, and 1 g/m2finished leather, for the innovative processes.The environmental sustainability of the proposed new processes increases from the solution with drums (and less water and chromium) to that utilising spray nozzles and aerosol rooms. A great improving can be obtained even just with the “simple” new drum solution, able to reduce the Human toxicity-cancer potential up to 53 % and Resource use-minerals and metals potential up to 42 %.

Preparation and properties of electromagnetic shielding leather based on magnetic MgFeCr-LDHs

Leather, as a kind of renewable biomass, is naturally rich in dipoles as well as excellent 3D fiber structure, which provides the possibility for its application in electromagnetic shielding field. This study combined the utilization of chromium-containing wastewater with the intelligent development of leather. Nano zero-valent iron (NZVI) was innovatively used to prepare magnetic Mg/Fe/Cr layered double hydroxide (MgFeCr-LDHs) by co-precipitation method while treating chromium wastewater. And magnetic MgFeCr-LDHs was used for tanning leather, which prepared electromagnetic shield leather (MgFeCr-LDHs/L). Fe3+ and Cr3+ in MgFeCr-LDHs were closely bonded with the active groups on collagen fibers by chemical bonding, which give leather hygrothermal stability. The shrinkage temperature of MgFeCr-LDHs/L reached 89.1°C. Electromagnetic shielding efficiency of magnetic MgFeCr-LDHs/L reached 25 dB due to MgFeCr-LDHs had better dielectric and magnetic losses to electromagnetic waves. Magnetic MgFeCr-LDHs/L also had good softness and mechanical properties. In summary, we expect magnetic MgFeCr-LDHs/L to be used as a wearable material in the field of electromagnetic shielding.

Accurately recognizing chromium species with multi-functionalized nano Au-based sensor array

High-resolution identification of chromium (Cr) species, especially various organic-Cr complexes, in a convenient and economically-feasible manner is the prerequisite for achieving the advanced treatment of chromium wastewater. To this end, a colorimetric nano-Au sensor array was developed by taking advantage of the UV-spectra shift of gold nanoparticles (Au NPs) upon interaction with Cr species; specifically, four molecular modifiers [i.e., iminodiacetic acid (IDA), tripolyphosphate (TPP), cetyltrimethylammonium bromide (CTAB), and 1,5-diphenylcarbazide (DPC)] were intentionally employed for assembling nano-Au array receptors, which showed respective responses toward different Cr species through the formation of coordination, hydrophobic interaction, electrostatic attraction, and redox reaction, respectively; the “fingerprint” differences of the unique optical properties were then integrated for semi-quantitatively recognizing Cr species by pattern recognition techniques. Eleven ubiquitous Cr species [i.e., Cr(III), Cr(VI), and various Cr(III)-organic complexes] served as the model samples, which could be sensitively identified, no matter in individual or mixture mode, by the developed nano-Au sensor array on the basis of the colorimetric responses resulted from diverse nano-Au-aggregation behaviors, with excellent anti-interference ability in the simulated or actual water scenario. Attractively, the nano-Au sensor array can achieve very sensitive detection limit of the quantitative analyses of Cr species in a prompt in-situ manner, which usually requires a two-step process of separation and detection for the conventional analytical methods. Such a convenient strategy of Cr species discrimination conduces to rationally designing specific protocols for the advanced treatment of chromium wastewater.

Chromium adsorption studies of CaCO3 intercalated N-tert-amyl acrylamide-co-acrylamide/AMPS hydrogels

In enterprises that produce a lot of chromium wastewater that cause harmful effect to the environment and human health. This research aims to pay expressively to the field by proposing a unique and effective solution to the ongoing experiment of chromium contamination in water and wastewater employing CaCO3 Nanocomposite hydrogels. The hydrogel’s fundamental changes have been characterized using techniques such as FTIR, XRD, TGA and SEM. Batch experiments systematically investigated key parameters, including contact time (60–360 min), initial ion concentration (50–500 ppm), pH (2–6), and adsorbent dose (0.1–0.5 g). Results showcased an impressive 96 % efficiency in chromium ion removal. Analysis utilizing Langmuir (R2 = 0.9382) and Freundlich (R2 = 0.9986) isotherm models, alongside pseudo-first (R2 = 0.9487) and pseudo-second-order (R2 = 0.9999) kinetics studies, revealed insightful patterns. Our findings demonstrate a favorable fit with the Freundlich isotherm, suggesting a strong attraction between the adsorbent and the metal ions. Additionally, kinetic studies indicate that the adsorption process adheres to pseudo-second-order kinetics. These results collectively suggest that the prepared hydrogel presents a viable and sustainable option for wastewater treatment, particularly in areas where conventional treatment methods may not be feasible due to cost or a lack of infrastructure.

Iron-based materials functionalized with carbon and phosphorus recovered from sludge enhanced the formation of stable minerals to passivate lead and chromium in wastewater and soil

The bioaccumulation and toxicity of heavy metals are serious threats to human activities and ecological health. The exploitation of environmentally friendly passivated materials is major importance for the remediation of heavy metal contaminated soil. This research developed a new type of environmental functional material with a core-shell structure, which is an iron-based material functionalized with phosphorus and carbon from sludge for heavy metal pollution remediation. The results indicated that the C/P@Fe exhibits excellent heavy metal removal ability, and the maximum removal rates of the two heavy metals in simulated wastewater could reach 100% under optimum reaction conditions. It also effectively converts the labile Cr/Pb into the stable fraction after 28 days of incubation, which increased the maximum residual fraction percentage of Cr and Pb by 32.43% and 160% in soil. Further analysis found that the carbon layer wrapped around the iron base could improve the electron transport efficiency of reducing iron, phosphorus and ferrum could react with heavy metal ions to form stable minerals, such as FeCr2O4, FeO·Cr2O3, Pb5(PO4)3OH, PbCO3, 2PbCO3·Pb(OH)2 and PbS, after reacting with C/P@Fe. The study demonstrated that the Iron-based materials functionalized with carbon and phosphorus from sludge provided a more efficient way to remove heavy metals.

Enhancement of Mass Transfer Process for Photocatalytic Reduction in Cr(VI) by Electric Field Assistance.

The removal of Cr(VI), a highly-toxic heavy metal, from industrial wastewater is a critical issue in water treatment research. Photocatalysis, a promising technology to solve the Cr(VI) pollution problem, requires urgent and continuous improvement to enhance its performance. To address this need, an electric field-assisted photocatalytic system (PCS) was proposed to meet the growing demand for industrial wastewater treatment. Firstly, we selected PAF-54, a nitrogen-rich porous organic polymer, as the PCS's catalytic material. PAF-54 exhibits a large adsorption capacity (189 mg/g) for Cr(VI) oxyanions through hydrogen bonding and electrostatic interaction. It was then coated on carbon paper (CP) and used as the photocatalytic electrode. The synergy between capacitive deionization (CDI) and photocatalysis significantly promotes the photoreduction of Cr(VI). The photocatalytic performance was enhanced due to the electric field's influence on the mass transfer process, which could strengthen the enrichment of Cr(VI) oxyanions and the repulsion of Cr(III) cations on the surface of PAF-54/CP electrode. In addition, the PCS system demonstrates excellent recyclability and stability, making it a promising candidate for chromium wastewater treatment.

Bioelectrochemical biosensors for water quality assessment and wastewater monitoring.

Bioelectrochemical biosensors offer a promising approach for real-time monitoring of industrial bioprocesses. Many bioelectrochemical biosensors do not require additional labelling reagents for target molecules. This simplifies the monitoring process, reduces costs, and minimizes potential contamination risks. Advancements in materials science and microfabrication technologies are paving the way for smaller, more portable bioelectrochemical biosensors. This opens doors for integration into existing bioprocessing equipment and facilitates on-site, real-time monitoring capabilities. Biosensors can be designed to detect specific heavy metals such as lead, mercury, or chromium in wastewater. Early detection allows for the implementation of appropriate removal techniques before they reach the environment. Despite these challenges, bioelectrochemical biosensors offer a significant leap forward in wastewater monitoring. As research continues to improve their robustness, selectivity, and cost-effectiveness, they have the potential to become a cornerstone of efficient and sustainable wastewater treatment practices.

Synergistic effect of adsorption-photocatalytic reduction of Cr(VI) in wastewater with biochar/TiO2 composite under simulated sunlight illumination.

Photocatalysis, which is an alternative technology to conventional methods, utilizes solar energy as the driving force to address environmental concerns and has attracted widespread attention from chemists worldwide. In this study, a series of photocatalytic materials composed of agricultural waste and titanium dioxide (TiO2) nanomaterial was prepared for the synergistic adsorption-photocatalytic reduction of hexavalent chromium in wastewater under mild conditions. The results showed that the TiO2 nanomaterial exhibited a higher photogenerated carrier separation efficiency and performance for the adsorption-photocatalytic reduction of Cr(VI) after loading straw biochar (BC). When the loading amount of BC was 0.025 g (i.e., TBC-3), the removal efficiency of Cr(VI) was as high as 99.9% under sunlight irradiation for 25 min, which was 2.9 and 3.5 times higher than that of pure TiO2 and BC samples, respectively. Additionally, after four cycles of experiments, the removal efficiency of Cr(VI) by TBC-3 remained at about 93.0%, proving its good chemical ability in our reaction system. Its excellent adsorption-photocatalytic performance is mainly attributed to the synergistic effect of the strong adsorption of BC and the outstanding photocatalytic performance of TiO2. Finally, the possible mechanism for the synergistic adsorption-photocatalytic reduction on BC/TiO2 to remove the highly toxic Cr(VI) in wastewater was proposed.

Synthesis of N-GQDs/CuS/Cv-CNNs hydrogels and their performance in hexavalent chromium wastewater treatment

The different types of point defects effectively enhance the adsorption and photocatalytic capacity of the N-GCC hydrogel, and the hydrogel structure has the ability to mitigate the risk of the material causing cuproptosis to life forms in nature.

Fortalecimiento de la competencia para el desarrollo sostenible análisis crítico: Aplicación de un ambiente virtual de aprendizaje.

Education for Sustainable Development provides students with values, attitudes and knowledge in order to provide alternative solutions to the social, environmental and economic challenges that may be occurring in the present and in the future. The objective of this article is to illustrate the process of strengthening the competence for sustainable development Critical Analysis, which is made up of the components of critical thinking, ethical and intellectual commitment; this development was carried out through the implementation of a Virtual Learning Environment, which consisted of three modules related to: the pollution of the Tunjuelo River, the Tannery Industry in San Benito and the Hybrid Method (which involves the use of chemical precipitation with Magnesium Oxide and the use of a solid residue from the Wet-Blue tannery industry for the removal of chromium in wastewater from the tanning stage). The type of research paradigm was qualitative, with a descriptive scope, which was developed with a group of Initial Teacher Training, belonging to the Bachelor's Degree in Natural Sciences and Environmental Education of the Public Pedagogical University of Kennedy; to evaluate the strengthening of this competence, three indicators are presented (1- Understands that knowledge is incomplete and is tinged with subjectivity; 2- Understands that every system (economic, social and environmental) presents dysfunctions that can be identified and corrected 3- Recognizes the social, economic and environmental dysfunctions that oppose sustainable development, Proposes alternatives for improvement) and their respective levels, according to the answers provided by the participating population. Within the results obtained there is evidence of a progression in the levels from passing to outstanding, which make up the indicators.

Removal of chromium from aqueous solution using a nanocomposite of nickel ferrite and polyaniline doped with 2-naphthalene sulfonic acid

Chromium is a highly toxic, highly mobile heavy metal commonly found in industrial effluents. This study investigated the efficacy of a nickel ferrite/polyaniline/2-naphthalene sulfonic acid nanocomposite (PANI-NSA/NiFe2O4) in removing Cr(VI) from solution. NSA doping led to the formation of tubular-shaped rods, enhancing the material's surface area. Key adsorption parameters (pH, adsorbent dosage, agitation time, and initial pollutant concentration) were thoroughly examined and optimized. The adsorption process was notably pH-dependent, with maximal adsorption occurring at pH 2. The findings indicated a remarkable 99.9% removal of Cr(VI) from a 50 mg/L solution with a 25 mg adsorbent dose. Freundlich, Langmuir, and Two-Surface Langmuir isotherm models were tested, with the Two-Surface Langmuir model best describing the experimental results. Kinetics studies revealed rapid adsorption within the initial 30 min, followed by a slower rate, reaching maximum Cr(VI) removal within 24 h. Temperature studies revealed and enhanced adsorption capacity at higher temperatures, with a maximum adsorption capacity of 420.0 mg/g at 45 °C. Thermodynamic analysis indicated an endothermic and spontaneous adsorption process. The mechanism of Cr(VI) removal involved electrostatic attraction, reduction, and surface complexation. PANI-NSA/NiFe2O4 could be reused for up to five cycles, achieving 99% Cr(VI) removal from a 50 mg/L Cr(VI) solution in the first two cycles. Furthermore, tests on authentic chromium wastewater showed that a 40 mg dose in 50 mL liquid fully removed 50 mg/L Cr(VI). This study underscores the potential of PANI-NSA/NiFe2O4 for industrial applications in Cr(VI) removal, offering a promising solution for addressing the pressing issue of chromium pollution.

Rapid reduction of aqueous Cr(VI) by oxalic acid on N-doped lignin charcoal: A significant contribution of structural defects and electronic shuttle effect

Rapid reduction of aqueous Cr(VI) to Cr(III) with waste biomass N-doped lignin charcoals (PLCNx) as a catalyst via mediate oxalic acid (OA) for hexavalent chromium wastewater. The experiment results showed that the PLCN20 composite had the greatest capacity for removing Cr(VI), and the removal rate of Cr(VI) kept higher than 98% when the addition of 5 mM OA in the system. The bubble-shaped structures of PLCNx could act as an electron shuttle mediating the electron transfer and participate in the reduction of Cr(VI), and the N vacancies defects and graphitic N on its surface were a premise for initiating the Cr(VI) reduction process. More importantly, the formation of the Cr(VI)-OA complex facilitated electron transfer as well, which significantly enhanced Cr(VI) reduction. The combined effects of the electron-donating ability of OA and the catalysis of Cr(VI)-OA complex, lead to the enhancement of Cr(VI) reduction on the PLCNx. This work not only offers novel insights into the synthesis of a superior high-efficiency heterostructure for catalyst but also proposes one new mechanism of PLCNx activate OA enhanced catalysis capacity, which helps design and optimize the catalyst process.

Efficient removal of chromium by a novel biochar-microalga complex: Mechanism and performance

The biochar has been considered as a high-efficiency bio-adsorbent for treating heavy metal wastewater. Microalgae are abundant in various aquatic systems, and carry specific functional groups on their surfaces that could also aid chromium removal (i.e., -COOH, -OH, -CHO, -O-). The previous studies have focused on metal uptake from wastewater by biochar, few have conducted in-depth research on its removal mechanism and performance to heavy metals when combined with microalgae. Here, the comprehensive study revealed chromium functional diversity and adsorption mechanisms on Coconut shell activated carbon (Csac) loaded with microalgae Chlorella (Csac@Chlorella) in greater detail than ever before. The chromium treatability of 0.5 Csac@1.0 Chlorella immobilized complex to electroplating chromium wastewater were 28.95% and 30.16% great higher than that of 0.5 Csac and 1.0 Chlorella in 120 min, respectively. And the adsorption equilibrium time was also significantly shortened to 20–40 min. This study further investigated the effect of Csac@Chlorella immobilized complex on chromium removal for electroplating chromium wastewater (the Cr removal ability of 0.5 Csac@1.0 Chlorella was 70.94%) and several potential influencing factors (i.e., t, pH, dosage). We identified carboxyl, carbonyl, cyanide ions and hydroxyl functional sites and found the chromium proportion in these functional groups were varied. Carboxyl and hydroxyl were the main groups that reacted with chromium, followed by carbonyl and cyanide ions. This study clearly indicated that a novel biochar-microalga immobilized complex could enhance the adsorption capacity of chromium, which have significant implications for the application of Csac@Chlorella biological resources in aquatic environment.

Integrated photocatalysis-adsorption method for chromium wastewater treatment

Nowadays, the development of TiO2-based composite materials has received much attention as part of an effort to increase TiO2′s photocatalytic activity so that it can be used in large-scale waste treatment. TiO2-natural zeolite (TiO2-NZ) hybrid composites, as an integrated photocatalysis-adsorption system, have been synthesized using the sol-gel method with varied zeolite masses (1.5, 3.0, and 4.5 g). The photodegradation of Cr(VI) by TiO2-NZ composites was tested, and it was discovered that the sample with a variation of 1.5 g zeolite (TiO2-NZ/1.5) produced the highest Cr(VI) degradation. The combination of natural zeolite adsorption and TiO2 photocatalytic properties has resulted in an increase in the material's photocatalytic ability to degrade Cr(VI). The TiO2-NZ/1.5 sample has the highest Cr(VI) removal rate of up to 97 percent, according to our findings. Crystal changes, morphology, porosity, elemental composition, and optical properties of the composite with superior performance were investigated using XRD, SEM-EDS, the N2-adsorption-desorption isotherm, and UV–vis DRS. TiO2 synthesized by the sol-gel method was in the anatase phase and successfully immobilized on the zeolite surface. The incorporation of TiO2 on the surface of the zeolite has suppressed the crystal size and band gap energy of TiO2. On the other hand, the presence of TiO2 has increased the specific surface area of the zeolite. In general, a larger specific surface area can show better adsorption ability and provide more active sites in photocatalytic reactions.

Reduction of Chromium in Waste Water From Hard Chrome Plating Processes: A Review

Waste water from hard chrome is considered to be highly toxic due to the presence of chromium ions in hexavalent form and this hexavalent state of chromium is more toxic to animals and humans due to its ability to produce reactive oxygen species in cells. Such heavy metals are considered as carcinogenic to living organisms and hence either reduction of ions to trivalent chromium or removal of ions has to be done before ejecting the waste water into the environment. Many processes for reduction, neutralisation and removal of hexavalent chromium have been investigated and reviewed extensively. In the present review, studies and research carried out for the removal of chromium from waste water of hard chrome plating effluent are summarised. The study was carried out on the aspects such as percentage removal, efficiency and optimum operating conditions in chrome removal and reduction processes.

Retraction: Treatment mechanism of hexavalent chromium wastewater in constructed wetland-microbial fuel cell coupling system

Following the publication of the above article we received concerns regarding the reliability and completeness of the methodology and data presented in the article. An investigation was conducted in accordance with Frontiers' policies and it was determined that the scientific validity of the article could not be rectified with a correction; therefore, the article has been retracted. This retraction was approved by the Chief Editors of Frontiers in Environmental Science ( and the Chief Executive Editor of Frontiers). The authors agreed/did not agree to this retraction.

Synthesis of Carbon from Rice Groats at Various Pyrolysis Temperatures and Its Application for the Recovery of Chromium Wastewater from the Tannery Industry

The research on synthesis of carbon from rice groats at various pyrolysis temperatures and its application for the recovery of chromium wastewater from the tannery industry by varying pyrolysis temperatures at 300, 400, and 500 °C. The results of carbon synthesis are analyzed in the form of determination of yield, water content, ash content, and iodine number. The best pyrolysis condition with the quality requirement of carbon is at a pyrolysis temperature of 500 °C with 760 mg.g-1 (iodine number). Adsorption kinetics was also carried out to determine the adsorption kinetics of chromium ions from tannery wastewater. Adsorption kinetics model of chromium wastewater from the tannery industry corresponds to the pseudo-second-order kinetics model with R2 is 0.9857, k2 is 0.0093 g.mg-1.min-1, and qe is 28.5714 mg.g-1.

Removal of total chromium in wastewater via simultaneous photocatalysis and adsorption using calcium silicate hydrate-based composites

Converting Cr(vi) to Cr(iii) and subsequent precipitation of Cr(iii) represents an efficient approach for wastewater treatment.