Hexavalent Chromium Ions Research Articles

Adsorption Performance for Chromium(VI) of a UiO-66-Ce Metal-Organic Framework Built by DL-Aspartic Acid.

Metal-organic frameworks (MOFs) have recently received a lot of interest for their use in adsorbing and eliminating hexavalent chromium from water. Obtaining low-cost, biocompatible, and environmentally friendly MOFs for research in this field is vital. One very stable three-dimensional UiO-66-Ce(IV) MOF, Ce-asp, was synthesized with a high yield using an amino acid ligand, DL-aspartic acid. As a result, the adsorption characteristics of the MOF against hexavalent chromium ions in aqueous solution were examined. The effects of time, solution pH, MOF dose, and beginning chromium(VI) content in aqueous solution were investigated on adsorption. More crucially, the adsorption mechanism of this MOF for chromium(VI) was proposed, setting the groundwork for its future use in chromium(VI) removal in real-world waters.

Synthesis and characterization of silver nanoparticle incorporated copolymer composite membrane for polymer enhanced ultrafiltration of hexavalent chromium ions from water

Synthesis and characterization of silver nanoparticle incorporated copolymer composite membrane for polymer enhanced ultrafiltration of hexavalent chromium ions from water

Construction of Stable 2D Cationic Breathing Ni-MOF for Cr(VI) Trapping and Electrochemical Sensing.

Pollution of surface water by heavy metal hexavalent chromium ions poses a serious threat to human health; herein, a two-dimensional (2D) cationic breathing Ni-MOF with free nitrate ions between the layers was designed and synthesized according to the characteristics of hexavalent chromium ions, {[Ni(L)2](NO3)2·5H2O}n (L = 1,3,5-tris[4-(imidazol-1-yl)phenyl]benzene). The flexible layer spacing of the 2D breathing Ni-MOF allows the exchange of NO3- by CrO42- without destroying the original structure. Electrostatic and hydrogen bonding interactions between CrO42- and Ni-MOF facilitate its exchange with NO3-. Moreover, CrO42- exhibits a higher binding energy with Ni-MOF compared to NO3-, and the hydrophobic channels of Ni-MOF favor CrO42- trapping due to its lower hydration energy. Consequently, Ni-MOF demonstrates both effective sorption and electrochemical sensing of Cr(VI), achieving a sensitivity of 2.091 μA μM-1 and a detection limit of 0.07 μM.

Exceptional light harvesting in copper doped CaTiO3 nanocuboids with surface nanosteps for the photo remediation of toxic Cr(VI) ions and dyes

Addressing the rising concerns of water pollution caused by harmful inorganic and organic contaminants is very crucial and photocatalysts with exceptional light harvesting capability are a promising way to tackle these issues. This study investigates the transformation of CaTiO3 into a visible light-active photocatalyst via copper doping. Copper-doped CaTiO3 nanocuboids were synthesized via a one-step solvothermal approach, resulting in the formation of distinctive nanostep substructures on the surface. Morphological analysis revealed the successful incorporation of copper ions into the perovskite matrix, as evidenced by the transition from smooth to rough, uneven surface features. X-ray diffraction confirmed the incorporation of Cu2+ ions into the Ti4+ site, while visible range absorption indicated a reduction in the bandgap. Furthermore, doping decreased the rate of charge carrier recombination and increased their average lifetime, prolonging the duration of active species. This modification facilitating efficient absorption of visible light and increase in the charge separation, leads to enhanced photocatalytic activity. The doped catalyst exhibited exceptional performance in the remediation of hexavalent chromium ions (98.5 % Cr6+ ions reduction to Cr3+ ions in 20 min), methylene blue (99.4 % degradation within 120 min), and eosin yellow (99.8 % degradation within 80 min) pollutants. This research underscores the potential of doping as a viable strategy for tailoring photocatalytic properties and addressing water pollution challenges.

BaTiO3 Nanoparticles for highly efficient piezocatalytic reduction of toxic hexavalent chromium: Synthesis, optimization, and kinetic study

Drinking water contamination with heavy metals from industrial activities is an important issue. In particular, the hexavalent chromium ions Cr (VI) which are classified as group (A) carcinogens. Our research reports an effective removal of hexavalent chromium from water through the use of BaTiO3 (BTO) as a piezocatalyst. We meticulously prepared pure tetragonal BTO by optimizing the synthesis parameters. The optimized BTO catalyst was utilized for the removal of Cr(VI) under applied mechanical force and removed up to 96 % of Cr(VI) from the solution. Our kinetic study revealed that the reaction follows a pseudo-first order. Thermodynamic studies indicated that the reaction is most spontaneous at temperatures of 20 °C and concentrations of 20 ppm. Our proposed mechanism for removing Cr(VI) by BTO piezocatalysts suggests that only 15 % of chromium was removed by adsorption, while the rest was removed by reduction through the piezocatalytic process.

CuMn2O4 anchored on mesoporous yttrium orthovanadate for the visible-light removal of hexavalent chromium ions in water

Recently, there has been significant interest in using one-dimensional nanomaterials for environmental cleanup in water sources, particularly for breaking down and eliminating harmful pollutants. Creating a reusable and effective photocatalyst poses a challenge in addressing semiconductor flaws such as instability and rapid recombination. This work discusses developing a highly responding photocatalyst by introducing varying quantities of CuMn2O4 (CMO) onto the surface of yttrium vanadate (YVO4) nanoparticles using the surfactant sol-gel method. The structures and morphology of these developed nanocomposites were verified using many characterization methods. The findings reveal that CMO is an electron trap within the dual system, which impedes charge carrier recombination and ameliorates photocatalytic performance. Their photocatalytic efficacy was evaluated through the photoreduction of Cr(VI) ions under visible illumination, revealing that adding CMO nanoparticles significantly boosts YVO4's photocatalytic activity. The Cr(VI) photoreduction follows a first-order reaction model. Among the tested photocatalysts, the 2.0 g/L dose of 9.0 % CMO-YVO4 demonstrated the most effective and reusable performance within 45 min. This sustained photocatalytic performance is credited to improved capture of light and effective transfer of charges resulting from the combination of CMO and YVO4.

Copper nanoclusters combined with polymer films as highly sensitive colorimetric probes for visual and proportional fluorescence detection of hexavalent chromium ions in pH and natural waters

In this study, a novel type of fluorescent nanocomposite film was prepared, which could be used for pH value sensing and detecting heavy metal hexavalent chromium ions. Copper nanoclusters doped into polyvinyl alcohol polyethylene glycol fluorescent nanocomposite film (CuNCs/PVA/PEG) has excellent fluorescent properties; it can not only be used as a pH sensor but also can selectively detect heavy metal hexavalent chromium ions. When pH>9, the CuNCs/PVA/PEG composite film will be quenched, which can be used as pH sensing. In addition, the CuNCs/PVA/PEG composite film can detect heavy metal hexavalent chromium ions with a detection line of 0.01 μM. It shows that the probe can detect Cr6+ quickly, sensitively, and selectively and has broad application prospects in environmental analysis applications.

Design of biocompatible gelatin hydrogels reinforced with magnetite nanoparticles: Effective removal of chromium from water environment

The development of biocompatible adsorbents is vital for environmental remediation to control and reduce pollution and waste accumulation in ecosystems. Biocompatible hydrogels represent an innovative class of materials that are primarily composed of polymer chain units forming their structural framework. They have a high affinity for water molecules. This research thus aims to incorporate iron oxide particles into the gelatin matrix to produce gelatin hydrogel beads to remove hexavalent chromium from an aqueous solution. The synthesized beads, known for their consistent size, low friction, high specific surface area, mechanical stability, and lightweight characteristics, demonstrated their suitability for various industrial applications. The effectiveness of these hydrogels in removing hexavalent chromium ions was confirmed through a thorough analysis using techniques such as FTIR, TGA, SEM, EDX, VSM, and XPS. Batch experiments revealed that the gelatin-based nanocomposite beads exhibited optimal adsorption efficiency under acidic conditions, lower initial concentrations of chromium ions, extended contact time, and elevated temperature (50–60 °C). The composite achieved a maximum removal efficiency of 99% at pH 1, with an adsorbent dose of 0.5 g at 50 °C, and an initial concentration of 50 mg per liter. The use of 0.7 N NaOH in the regeneration process resulted in a commendable 70.5% desorption efficiency, enabling potential reuse and regeneration. Significantly, the desorption efficiency remained consistently high even after four desorption-readsorption cycles, contributing to the economic and environmental sustainability of chromium removal. Additionally, the study determined that the sorption process was feasible, spontaneous, and endothermic. These collective findings suggest that magnetic gelatin hydrogel beads could serve as a cost-effective alternative adsorbent for the efficient removal of chromium ions from aqueous solutions.

Utilization of Adsorbent Based on Rice Straw (<i>Oryza sativa</i>) for Cr(VI) Ions Reduction in Aqueous Solutions

In this study, we utilized an adsorbent based on rice straw for reducing hexavalent chromium ions (Cr (VI)) in an aqueous solution. The rice straw as adsorbent raw material was washed, dried, and powdered. Rice straw powder was heated at 450°C for 2 hours to obtain rice straw adsorbent. The adsorbent was activated with 1M H3PO4 for 4 hours. Characterization of the adsorbent was done using Fourier Transform Infra-Red (FTIR) method. FTIR spectra showed the presence of hydroxy, carboxylic, aromatic, and ether groups on the surface of the rice straw and the made adsorbent. The reduction of Cr (VI) ions in aqueous solutions was carried out using the adsorption batch method. The adsorption process was conducted in various the Cr (VI) solutions pH for 1-5 and variations in contact time for 5-720 minutes. The highest percentage reduction of Cr (VI) reached 66.90%. It has occurred at pH 2 and equilibrium at 600 minutes of contact time.

Aerogels of Polypyrrole/Tannic Acid with Nanofibrillated Cellulose for the Removal of Hexavalent Chromium Ions.

The preparation of conducting polymer aerogels is an effective strategy to produce innovative materials with enhanced physicochemical properties. Herein, polypyrrole (PPy) aerogels were oxidatively prepared in the presence of tannic acid (TA) with different concentrations (2.5, 5, and 10% mole ratio to pyrrole monomer) under freezing conditions. Nanofibrillated cellulose (NFC) was added during the PPy/TA synthesis to enhance mechanical stability. The effect of TA concentration on the aerogels' morphology, conductivity, thermal stability, and adsorption capacity was investigated. The conductivity of 9.6 ± 1.7 S cm-1 was achieved for PPy/TA prepared with 2.5% TA, which decreased to 0.07 ± 0.01 S cm-1 when 10% TA was used. PPy/TA aerogels have shown high efficacy in removing Cr(VI) ions from aqueous solutions. Adsorption experiments revealed that all the aerogels follow pseudo-second-order kinetics. PPy/TA prepared with NFC has a maximum adsorption capacity of 549.5 mg g-1.

Colorimetric Sensor for Cr(VI) Ion Detection in Tap Water Using a Combination of AuNPs and AgNPs.

Colorimetric sensors are a promising technique for the simple screening of water, food, and environmental samples contaminated with interferents, allowing for color changes to be observed with the naked eye or a spectrophotometer. In this study, a colorimetric sensor for the selective detection of hexavalent chromium ion (Cr(VI)) contamination in water was developed. A combination of sodium borohydride-coated gold and citrate-capped silver nanoparticles (Na-AuNPs/cit-AgNPs) was employed as a colorimetric probe. Upon the addition of Cr(VI)-contaminated tap water in the colorimetric probe solution, the color sequentially transitioned from its initial orange to dark reddish-purple, dark purplish-red, dark blue-violet, and gray. This colorimetric strategy relies on AgNP dissolution and AuNP aggregation in the presence of the Cr(VI) ions. The dissolution of AgNPs is evidenced by the reduction of the characteristic peak of AgNPs at 400 nm, while the aggregation of AuNPs leads to a red shift in the absorption band at 514 nm, accompanied by broad absorption in the 500-700 nm range. The limits of detections were found to be 22.9 and 50 ppb using a spectrometer and by visual observation, respectively. The synthesized AuNPs and AgNPs are very stable in the presence of media containing complicated ions. We further demonstrated the practical applicability of the developed system for detecting Cr(VI) in real samples, including natural water and artificial urine, highlighting its potential for addressing Cr(VI) contamination in practical scenarios.

Effective adsorptive uptake of hexavalent chromium ions from aqueous systems utilizing a superior activated nanobentonite@cobalt ferrite@carboxymethylcellulose nanocomposite

Contamination of industrial and dietary water with Cr(VI) ions is known as a global concern. Industrial wastes containing elevated Cr(VI) concentration are hazardous and harmful to people and animals, if inappropriately treated. Consequently, in the current research, a novel nanocomposite of activated nanobentonite@cobalt ferrite@carboxymethylcellulose (ANB@CoFe2O4@CMC) is generated and characterized. Several characterization techniques were employed to confirm the structure of as-prepared ANB@CoFe2O4@CMC. The mean particle size range of this nanocomposite was found to be 22.5–26.2 nm. Through batch adsorption assessments, ANB@CoFe2O4@CMC was employed and optimized to remove Cr(VI) ions from aquatic medium providing optimum conditions of pH 2.0, 25–30 min shaking time, 25 mg nanocomposite dosage at 25 °C reaction temperature. Freundlich model was extremely relevant via linear and nonlinear expression. Thermodynamic investigations were investigated to conclude that both exothermal and spontaneous tendencies in governing Cr(VI) adsorptive uptake. The ANB@CoFe2O4@CMC was remarkably stable after five subsequent runs of regenerating and recycling. This investigation displayed the potential of ANB@CoFe2O4@CMC as a powerful nanocomposite material for Cr(VI) recovery from diverse waters via a microcolum technique, exhibiting uptake values up to 87.9–95.8 %. As a result, the evaluated ANB@CoFe2O4@CMC could be successfully illustrated a superior material for effective multi-uptake Cr(VI) ions from water.

Tm3+/Yb3+:NaGdF4 nanoparticles decorated g-C3N4/BiOBr0.75I0.25 multicomponent heterostructure: Structural, optical properties and UV–Visible-NIR responsive photocatalytic degradation of Rhodamine B and reduction of Cr(VI)

A wide solar spectral range responsive multicomponent heterostructure photocatalyst NGT/g-C3N4/BiOBr0.75I0.25 was successfully synthesized and used for the UV–visible-NIR photodegradation of the dye Rhodamine B and photoreduction of highly toxic hexavalent chromium ions. Our study shows that the heterostructure overcomes the drawbacks of limited visible-light absorption and fast charge recombination of g-C3N4. Herein, the incorporation of BiOBr0.75I0.25 extends the absorption in the visible region and endorses the separation rate of photogenerated charge carriers. Additionally, the upconversion nanoparticles NaGdF4: Tm/Yb (NGT) with its higher infrared light absorption capacity and characteristic emission spectral overlapping with absorption range of g-C3N4/BiOBr0.75I0.25 nanocomposite, further facilitates the photocatalytic activity of the NGT/g-C3N4/BiOBr0.75I0.25 heterostructured nanocomposite. Extensive structural, morphological, and compositional analysis was done using XRD, TEM, SEM, FE-SEM, XPS, and FTIR measurements. The PL emission, time-resolved decay, and electrochemical impedance spectroscopy were used to probe the separation rate of photogenerated electron-hole pairs and efficient energy transfer in NGT/g-C3N4/BiOBr0.75I0.25 heterostructured nanocomposite. The possible photocatalytic degradation mechanism was comprehensively proposed through a combination of UV–Vis absorption, Mott Schottky, and scavenger test analysis. The photodegradation efficiency of the heterojunction was 98 %, which is much higher than the bare g-C3N4 (74 %). Moreover, the heterostructure exhibited excellent long-term reusability, maintaining the photodegradation efficiency of 97.02 % even after four consecutive degradation cycles, establishing it as a preferable material for photocatalytic dye degradation. Additionally, NGT/g-C3N4/BiOBr0.75I0.25 heterostructured nanocomposite also demonstated better performance for the photoreduction of Cr(VI) to Cr(III), achieving photocatalytic efficiency of 98.86 % under acidic condition.

Synthesis of polyvinylpyrrolidone-protected silver nanoclusters with strong fluorescence for highly sensitive and selective hexavalent chromium ion detection

Synthesis of polyvinylpyrrolidone-protected silver nanoclusters with strong fluorescence for highly sensitive and selective hexavalent chromium ion detection

Efficient Cr(VI) remediation by electrospun composite porous nanofibers incorporating biomass with metal oxides and metal-organic framework

To develop a highly efficient adsorbent to remediate and remove hexavalent chromium ions (Cr(VI)) from polluted water, cellulose acetate (CA) and chitosan (CS), along with metal oxides (titanium dioxide (TiO2) and ferroferric oxide (Fe3O4)), and a zirconium-based metal-organic framework (UiO-66) were used to fabricate the composite porous nanofiber membranes through electrospinning. The adsorption performance, influencing factors, adsorption kinetics and isotherms of composite nanofiber membranes were comprehensively investigated. The multi-layer membrane with interpenetrating nanofibers and surface functional groups enhanced the natural physical adsorption and provided potential chemical sites. The thermal stability was improved by introducing TiO2 and UiO-66. CA/CS/UiO-66 exhibited the highest adsorption capacity (118.81 mg g−1) and removal rate (60.76%), which were twice higher than those of the control. The correlation coefficients (R2) of all the composite nanofibers regressed by the Langmuir model were significantly higher than those by the Freundlich model. The pseudo-first-order kinetic curve of CA/CS composite nanofibers showed the highest R2 (0.973), demonstrating that the whole adsorption process involved a combination of strong physical adsorption and weak chemical adsorption by the amino groups of CS. However, the R2 values of the pseudo-second-order kinetic model increased after incorporating TiO2, Fe3O4, and UiO-66 into the CA/CS composite nanofiber membranes since an enhanced chemical reaction with Cr (VI) occured during the adsorption

A promising approach for the removal of hexavalent and trivalent chromium from aqueous solution using low-cost biomaterial.

Heavy metal pollution is an enduring environmental challenge that calls for sustainable and eco-friendly solutions. One promising approach is to harness discarded plant biomass as a highly efficient environmental friendly adsorbents. In this context, a noteworthy study has spotlighted the employment of Euryale ferox Salisbury seed coat (E.feroxSC) for the exclusion of trivalent and hexavalent chromium ions. This study aims to transform discarded plant residue into a novel, environmentally friendly, and cost-effective alternative adsorbent, offering a compelling alternative to more expensive adsorption methods. By repurposing natural materials, we can contribute to mitigating heavy-metal pollution while promoting sustainable and economically viable solutions in environmental remediation. The effect of different parameters, i.e., chromium ions' initial concentration (5-25mg L-1), solution pH (2-7), adsorbent dosage (0.2-2.4g L-1), contact time (20-240min), and temperature (298-313K), were investigated. E.feroxSC proved highly effective, achieving 96.5% removal of Cr(III) ions at pH 6 and 97.7% removal of Cr(VI) ions at pH 2, with a maximum biosorption capacity of 18.33mg/g for Cr(III) and 13.64mg/g for Cr(VI), making it a promising, eco-friendly adsorbent for tackling heavy-metal pollution. The adsorption process followed the pseudo-second-order kinetic model, aligning well with the Langmuir isotherm, exhibited favorable thermodynamics, and was characterized as feasible, spontaneous, and endothermic with physisorption mechanisms. The investigation revealed that E.feroxSC effectively adsorbed Cr(VI) which could be rejuvenated in a basic solution with minimal depletion in its adsorption capacity. Conversely, E.feroxSC's adsorption of Cr(III) demanded rejuvenation in an acidic milieu, exhibiting comparatively less efficient restoration.

Power benefitted bioremediation of hexavalent chromium ions in biochar blended soil microbial fuel cell

Power benefitted bioremediation of hexavalent chromium ions in biochar blended soil microbial fuel cell

Hexavalent chromium ion removal from wastewater using novel nanocomposite based on the impregnation of zero-valent iron nanoparticles into polyurethane foam

In this study, we developed a novel nanocomposite, polyurethane foam impregnated with zero-valent iron nanoparticles (PU@nZVI), for the effective removal of chromium(VI) from various water sources. The characterization of nanocomposite (PU@nZVI) was performed by XRD, SEM–EDS, TEM and FT-IR techniques. Using the response surface methodology, we optimized the removal conditions, achieving an optimal pH of 2 and a dose of 0.5 g/L. The PU@nZVI demonstrated an excellent maximum adsorption capacity of 600.0 mg/g for Cr6+. The adsorption kinetics and isotherms were best described by the pseudo-second-order model and the Freundlich isotherm, respectively. Significantly, the nanocomposite removed 99.98% of Cr6+ from tap water, 96.81% from industrial effluent, and 94.57% from treated sewage wastewater. Furthermore, the PU@nZVI maintained its efficiency over five adsorption–desorption cycles, highlighting its reusability. These results suggest that the PU@nZVI nanocomposite is a highly efficient and sustainable option for chromium(VI) removal in water treatment applications.

Tuning electrochemical behavior and band gap energy of ammonium phosphomolybdate/polymer composite and facilitate reduction of Cr(VI) in contaminated water

Binary composites of ammonium phosphomolybdate (APM) with polyaniline and poly(N-methylaniline) namely APM/PAni and APM/PNMAni were synthesized respectively in situ by exploiting the oxidizing ability of APM. The composites were characterized using fourier transform infrared spectroscopy, powder X-ray diffraction, and scanning electron microscopy. Further, the electrochemical behavior of these composites was investigated using cyclic voltammetry. The redox peaks obtained for APM, APM/PAni and APM/PNMAni at 0.302, 0.228 and 0.298 V respectively could be attributed to MoV/MoVI electron process. The appreciable shift in the peak could be attributed to the electron donating behavior of methyl groups in APM/PNMAni. Additionally, the band gap energy was calculated using diffuse reflectance spectroscopy data. The optical band gap of the composites increased considerably as compared to APM. A higher band gap was observed for APM/PNMAni as compared to APM/PAni, indicating the influence of methyl substitution in tuning the band gap energy. In addition, the role of these composites and its constituents in the removal of hexavalent chromium ions from aqueous solution was also explored. The removal of Cr(VI) from aqueous solution was monitored using UV–Visible spectroscopy. While removal of Cr(VI) as high as 96.3 % could be achieved using polymers, composites exhibited the ability to reduce toxic Cr(VI) moieties to environmentally benign Cr(III) ions.

Harnessing the power of polyethyleneimine in modifying chitosan surfaces for efficient anion dyes and hexavalent chromium removal

In this investigation, synthesis of a surface-functionalized chitosan known as amino-rich chitosan (ARCH) was achieved by successful modification of chitosan by polyethyleneimine (PEI). The synthesized ARCH was characterized by a specific surface area of 8.35 m2 g−1 and a microporous structure, with pore sizes predominantly under 25 nm. The Zeta potential of ARCH maintained a strong positive charge across a wide pH range of 3–11. These characteristics contribute to its high adsorption efficiency in aqueous solutions, demonstrated by its application in removing various anionic dyes, including erioglaucine disodium salt (EDS), methyl orange (MO), amaranth (ART), tartrazine (TTZ), and hexavalent chromium ions (Cr(VI)). The adsorption capacities (Qe) for these contaminants were measured at 1301.15 mg g−1 for EDS, 1025.45 mg g−1 for MO, 940.72 mg g−1 for ART, 732.96 mg g−1 for TTZ, and 350.15 mg g−1 for Cr(VI). A significant observation was the rapid attainment of adsorption equilibrium, occurring within 10 min for ARCH. The adsorption behavior was well-described by the Pseudo-second-order and Langmuir models. Thermodynamic studies indicated that the adsorption process is spontaneous and endothermic in nature. Additionally, an increase in temperature was found to enhance the adsorption capacity of ARCH. The material demonstrated robust stability and selective adsorption capabilities in varied conditions, including different organic compounds, pH environments, sodium salt presence, and in the face of interfering ions. After five cycles of adsorption, ARCH maintained about 60% of its initial adsorption capacity. Due to its efficient adsorption performance, simple synthesis process, low biological toxicity, and cost-effectiveness, ARCH is a promising candidate for future water treatment technologies.