Hazardous Hexavalent Chromium Research Articles

Development of Nickel-Chromium Alloy Electroplating and Its Surface Morphology Studies for Automobile Industries

In the electroplating industry, alloy plating is typically one of the most difficult processes. We are showcasing the Ni-Cr (Nickel Chromium) alloy electroplating in our work. Trivalent chromium bath is made in order to resist the hazardous hexavalent chromium, and co-deposition of chromium and nickel is accomplished. Our work is appropriate for industrial electroplating in the automotive industry because Ni-Cr alloy exhibits good corrosion resistance along with features including wear resistance, ductility, and thermal stability. Through the use of SEM (Scanning Electron Microscopy), EDAX (Energy Dispersive X-Ray Analysis), and XRD (X-Ray Diffraction) studies, we are able to clearly observe the surface morphology in this project. These research allow us to observe the Porous behavior surfaces. Figure 1

A review on the environment friendly electroplating of Cr (III) & Cr (VI)

Chromium plating process is the most effective way of protecting the base material against hostile environment or improving surface properties of base material. There are several problems with traditional chrome plating. Traditional process uses toxic acid baths and may cause various health conditions. The baths employed contain chromic acid in which the chromium is in the hexavalent state. Hexavalent chromium has been proved to have toxic, mutagenic and cancerogenic effects for human health. As a result, In Europe, the implementation of the reach initiative will increase fees on companies still using Cr (VI) in 2017 and will require action plans to phase out Cr (VI) in the future. This has left the plating industry in a very delicate position with dark future prospects unless new solutions that are both effective and environmentally friendly are discovered. Superchrome Physical Vapor Deposition coating ahead of looming industry regulatory actions that will drive towards the removal of hazardous hexavalent chromium compounds. These new sputtered chromium coatings do not require a protective paint top coat to pass exterior automotive trim specifications. Visually the chromium coatings match those of electroplated decorative chromium in color and appearance.

LED-enhanced photocatalytic reduction of hexavalent chromium by Cu-doped ZnO nanorods: kinetic modeling, cost analysis, and toxicity assessment

ABSTRACT This study unveils the synthesis and application of Cu-doped ZnO nanorods (NRS) as an efficient catalyst for the photocatalytic reduction of hazardous hexavalent chromium (Cr6+) in water. Synthesized via a simplified co-precipitation method, the NRS demonstrated enhanced performance, achieving an 89.35% Cr6+ reduction efficiency under optimal conditions. The catalyst’s performance was significantly augmented in the presence of hydrogen peroxide (H2O2) and revealed a first-order kinetic model. Radical trapping experiments highlighted the pivotal role of hydroxyl radicals in the photocatalytic process. A comparative analysis of the NRS with LED/ZnO and undoped ZnO underscores the superior efficiency of the Cu-doped variant. Moreover, the applicability of this system was validated in real water and wastewater matrices containing Cr6+, indicating its promising potential for industrial and environmental applications. An in vivo bioassay using Daphnia magna further confirmed the reduced toxicity post-treatment, underscoring the environmental friendliness of this innovative approach. The findings present Cu-doped ZnO nanorods as a promising, effective, and eco-friendly catalyst for the remediation of Cr6+ contaminated water, marking a significant stride towards sustainable and efficient water treatment solutions.

2D/3D MXene/NiFeMn-layered double hydroxide decorated gelatin for removal of Cr(VI) and Congo red: Performance and mechanism

The discharge of toxic heavy metals and dyes into water is considered a principal reason for ecosystem deterioration. Therefore, the development of versatile adsorbents that can treat this threat is an urgent issue. On this basis, we designed and characterized a novel Ti3C2TX/NiFeMn-LDH@Gel composite to aptly remove hazardous hexavalent chromium ions Cr(VI) and organic Congo red dye (CR). Ti3C2TX/NiFeMn-LDH@Gel composite was facilely synthesized by introducing NiFeMn-layered double hydroxide and Ti3C2TX MXene into gelatin via a cross-linking reaction. Experimental data revealed that raising Ti3C2TX amount to 10 % in the matrix has dramatically promoted the adsorption aptitude of Ti3C2TX/NiFeMn-LDH@Gel towards Cr(VI) and CR. Freundlich model best described Cr(VI) and CR adsorption, with qmax reaching 423.73 mg/g, and 588.24 mg/g, respectively. Additionally, the adsorption kinetics of Cr(VI) and CR were fitted to the pseudo-second order model accompanied with spontaneity, randomness, and endothermic behavior. In addition, stability, and selectivity of Ti3C2TX/NiFeMn-LDH@Gel were investigated. Effect of ionic strength and interfering ions were explored as well. Besides, the recyclability test inferred superb adsorption capacities towards Cr(VI) and CR till the 5th cycle, revealing the potentiality of Ti3C2TX/NiFeMn-LDH@Gel towards anionic contaminants removal.

Triphenylamine-based covalent triazine framework @ carbon nanotube complex: efficient photogenerated charges migration for metal free photocatalytic Cr(VI) reduction

Photocatalytic hazardous hexavalent chromium Cr(VI) reduces to nontoxic trivalent chromium Cr(III) by metal free catalytic system under visible light irradiation is a promising method to harness Cr(VI) pollution. However, the rate-determining step for these systems is still charge separation and transport from semiconductor to the surface active site due to high exciton binding energy and transport Schottky barrier. Herein, we present a novel composite catalyst by situ growth of two-dimensional triphenylamine-based covalent triazine framework (TACTF) semiconductor with one-dimensional (1D) carbon nanotube (CNT) electronic conductivity mediator. The resultant TACTF@CNT complex exhibits a lower Schottky barrier, which improves lateral charge transport and interlayer exciton dissociation though interconnections TACTF layers with CNT, assuring high efficiency of photogenerated charges transfer from TACTF semiconductor to the surface active site for subsequent photocatalytic Cr(VI) reduction. The TACTF@CNT shows an excellent photocatalytic activity for Cr(VI) reduction, and 100 % removal of Cr(VI) was observed under visible light irradiation for 2 h, which is remarkably superior to those of TACTF, CNT and their physical mixture.

Efficient Cr(vi) removal by expanded graphite synergized with oxalic acid under UV irradiation.

Expanded graphite (EG), an easily-obtained carbon material with the potential of transferring electrons, was utilized successfully in the removal of hazardous hexavalent chromium (Cr(vi)) by environment-friendly oxalic acid (Ox) under UV irradiation. EG with a unique worm-like structure was obtained via a facile microwave treatment. The results showed that the EG + Ox + UV system had optimum performance, removing 99.32% of the Cr(vi) (1 mM) within 60 min at pH = 3, and the kinetic rate constant of Cr(vi) elimination was 7.95 mol L-1 min-1. Three components are potentially involved in the Cr(vi) elimination mechanism by the EG + Ox + UV system: (1) the direct electron transfer (DET) pathway of the EG-Ox-Cr(vi) through the acceleration effect of EG caused the majority removal of Cr(vi) under UV; (2) ·CO2 - generated from Ox photolysis was used to reduce some Cr(vi); (3) ·CO2 - created from Cr(vi)-Ox complexes in the solution through the photoinduced electron transfer (PET) pathway also reduced a little Cr(vi). Overall, the efficient removal of Cr(vi) by the EG + Ox + UV system provided new ideas for future research on Cr(vi) treatment.

Simultaneous adsorption and fluorescent detection of Cr(VI) via lanthanide coordinating polymeric porous microparticles

Functional porous microparticles that enable simultaneous adsorption removal and online monitoring of hazardous hexavalent chromium are of great importance for effective remediation of Cr(VI) pollution. Herein, we have synthesized, for the first time, an oligomer bearing aromatic backbone and pendent carboxyl, sulfonate as well as amidoxime groups, which has been further employed as the dual functional ligand to coordinate with lanthanide ions of Tb3+ via a facile one-step solvent exchange induced self-assembling, leading to generation of the cube-like fluorescent porous microparticles. Thanks to their porous structure, abundant surface binding sites as well as green fluorescence emission that can be selectively quenched by Cr(VI), the obtained lanthanide coordinated polymeric porous microparticles exhibited both competitive adsorption and fluorescent detection of Cr(VI). More specifically, the optimized fluorescent porous microparticles demonstrated a maximum Cr(VI) adsorption capacity of 553.92 mg·g−1 and a limit of detection for Cr(VI) down to 1.92 nM according to systematic adsorption and detection experiments. On account of scalable synthesis of oligomer ligand, facile preparation of microparticles as well as their competitive dual adsorption and detection of Cr(VI), the current work basically opens new way for design and fabrication of advanced materials for heavy metal ions pollution controls.

Forecast of Phase Diagram for the Synthesis of a Complex for the Detection of Cr6+ Ions.

A new organic complex (ANNBA) was synthesized using the solvent-free, solid-state reaction involving anthranilamide (AN)–m-nitrobenzoic acid (NBA). The established phase diagram specifies the formation of a complex in a 1:1 stoichiometric ratio which melts congruently at 142 °C. The diagram also infers the formation of two eutectics, E1 and E2, on either side of the complex with their respective melting at 118 and 106 °C. The stability and novelty of the synthesized complex was confirmed by differential scanning calorimetry, powder X-ray diffraction, and spectroscopic FTIR, 1H, and 13C NMR studies. The significant thermodynamic parameters such as the heat of mixing, the entropy of fusion, the roughness parameter, the interfacial energy, and excess thermodynamic functions have been studied. The novel complex (ANNBA) material displayed intense fluorescent emission as compared to the parent and the other well-known fluorescent organic material “pyrene.” The influence of solvent’s polarity on the absorption and emission of the complex has been studied in different solvents. Herein, we have displayed remarkable affinity of the complex toward hexavalent chromium ions in water, affecting its fluorescent property. We have deployed the synthesized complex as a turn-off fluorescent sensor to detect the most hazardous hexavalent chromium ions in water for the first time.

Recycling of chromium sludge to promote aggregation and growth of metal during self-reduction of nickel laterite ore

Addition of stainless steel pickling sludge, which contains hazardous hexavalent chromium, to low-grade nickel laterite ore has the potential to eliminate the hexavalent chromium and promote the aggregation and growth of iron-nickel particles during reduction with anthracite. The effect of chromium sludge on the aggregation and growth of metal particles during a self-reduction process of nickel laterite ore has been studied. The detoxification effect of hexavalent chromium in the sludge was evaluated using the standard TRGS 613 leaching test. Results showed that with increasing chromium sludge addition, the size of metal particles increased. With the addition of 13.94% by mass chromium sludge the average metal particle size in the reduce ore increased from 0.42 µm to 1.38 µm while the recovery of Fe, Ni and Cr increased from 53.73%, 19.39% and 33.36% to 78.33%, 69.22% and 58.26%, respectively. It is proposed that a low melting point eutectic phase of FeS formed in the reduced products, significantly promoted the migration and aggregation of metal particles. Leaching tests indicated that the original chromium sludge released > 600 mg/kg Cr(VI) while the slag from the combined laterite and chromium sludge released less than the EPA limit of 2 mg/kg Cr(VI).

ZnO and Mn doped ZnO generated under three different synthesis conditions and photocatalytic reduction of hazardous hexavalent chromium by these photocatalysts

In this article, chemical coprecipitation strategy for synthesizing manganese doped zinc oxide under three different synthesis conditions such as room condition, in the presence of microwave radiation and under solar radiation is being discussed. The efficiency of doped zinc oxide thus produced as a photocatalyst in the reduction of hazardous hexavalent chromium, a hemotoxic, genotoxic as well as a potent carcinogenic species, is also being discussed. For aiding comparison of photocatalytic efficiency, pure undoped zinc oxide was also produced by chemical precipitation approach under these three different conditions. Synthesized products were characterized through X-ray diffraction analysis and energy dispersive X-ray analysis. In this study it was observed that catalysts produced under solar radiation possess higher efficiency.

Investigation of Ferrochromium Wastes for their Hazardous Hexavalent Chromium Content

In this study, ferrochromium slag (FS) and electric-arc furnace dust (EAFD) samples were examined for their hazardous hexavalent chromium content mainly by X-ray photoelectron spectroscopy (XPS) analysis. According to the experimental results, magnesium-silicate constitutes the main framework of both FS and EAFD samples. Highly crystalline FS contains 3.11%Cr2O3 as spinel phases while this constituent is much higher, 15.44%, in EAFD. The general XPS spectra show that both samples mainly consist of O, Mg and Si elements. In addition, FS also includes aluminum while carbon, calcium and potassium are the other major elements for EAFD. The peaks appeared in the range of 577-589 eV confirm chromium content of the samples. Besides, the peaks appeared at 1022 and 1045 eV point out zinc content of EAFD. Based on the XPS atomic ratio, Cr contents of FS and EAFD were obtained as 0.505 and 0.987%, respectively while EAFD further contains 2.594% Zn. The detailed XPS analysis indicates that chromium exists as two oxidation states, trivalent and hexavalent forms at 2p orbitals. Specifically, for 2p3/2 orbitals, trivalent and hexavalent chromium were assigned at 577.1 and 579.2 eV, respectively whereas 586.9 and 588.9 eV for 2p1/2 orbitals. Furthermore, the corresponding intensities of these peaks are much higher for EAFD. By comparing the peak intensities, the relative proportions of Cr (VI) were calculated as 49.44 and 49.53% for FS and EAFD, respectively. The leaching tests show that solubilities of all the metals examined except Cr are far below the toxicity limits for hazardous waste and even below the ranges of non-hazardous waste. Specifically, chromium contents of the filtrates were determined as 0.862 and 268.050 mg/l for FS and EAFD, respectively. Considering the toxicity limits of chromium, EAFD can be surely labeled as a highly hazardous waste whereas, on the other hand, FS is within the limits of non-hazardous waste. In conclusion, it can be said that the hazardous hexavalent chromium content must be reduced to immobile trivalent forms for the dust sample prior to disposed in landfills.

Activated biochars derived from wood biomass liquefaction residues for effective removal of hazardous hexavalent chromium from aquatic environments

AbstractResidues obtained after wood biomass liquefaction were used as precursors for the synthesis of two activated biochars. The source of biomass liquefaction constituted of industrial wood processing by‐products, including bark and wood sawdust. The liquefied residues were analyzed in terms of chemical components and structure. Carbonization under nitrogen atmosphere followed by physical CO2activation allowed to obtain microporous activated carbons with specific surface areas of 741 and 522 m2 g−1, and micropore volumes of 0.38 and 0.27 cm3 g−1, respectively. The obtained activated carbons were used to remove toxic hexavalent chromium from the aquatic environment. The observed sorption capacities were 80.6 mg g−1versus 36.7 mg g−1for wood bark‐derived and wood sawdust‐derived carbon, respectively, indicating a key role of the wood residue source in the effectiveness of Cr(VI) removal by resulting carbons. Despite the dominant microporous structure, the adsorption kinetics was surprisingly fast, especially for the bark‐derived carbon, since the adsorption equilibrium was reached within 2 h. The sorption mechanism of chromium was based on the carbon surface‐mediated reduction of toxic hexavalent form to its non‐toxic trivalent form, as confirmed by the X‐ray photoelectron analysis. Therefore, the residues from wood liquefaction can be easily converted into porous activated biocarbons capable of adsorbing significant amounts of hazardous Cr(VI) while reducing them to non‐toxic Cr(III).

Efficient catalytic reduction of hazardous hexavalent chromium by cobalt sulfide nanoparticles

Efficient catalytic reduction of hazardous hexavalent chromium by cobalt sulfide nanoparticles

Nano nickel embedded in N-doped CNTs-supported porous biochar for adsorption-reduction of hexavalent chromium

Nitrogen-doped carbon coated transition metal hybrids for the removal of hazardous hexavalent chromium (Cr(VI)) has attracted increasing attention in wastewater treatment recently. In this study, three-dimensional nano-nickel particles embedded in N-doped carbon nanotubes supported on porous biochar (Ni@N-K-C) were synthesized by a two-stage strategy of KOH activation followed by annealing. The effect of KOH activation treatment on the doping process and Cr(VI) removal properties were investigated. The results indicate that KOH activation can improve the pore parameters and promote subsequent doping of Ni and N and the growth of carbon nanotubes (CNTs). After KOH pretreatment, the specific surface area of Ni@N-K-C increased significantly to 604.62 m2/g. The improved pore structure accelerates the mass diffusion of Cr(VI) ions and provides an available surface for the adsorption and reduction of Cr(VI). Therefore, the Ni@N-K-C obtained at 900 °C showed a high removal capacity for Cr(VI) (824.4 mg/g) and a stronger ability to reduce to Cr(III).

Synergetic formulation of Cyanex 272/Cyanex 302 for hexavalent chromium removal from electroplating wastewater

Hazardous hexavalent chromium (Cr(VI)) released from the electroplating industry beyond the discharge concentration limit has created great concern worldwide. Solvent extraction (SX) is an effective method for metal separation from an aqueous system. Throughout this work, novel synergistic solvent extraction of Cr(VI) from rinsed electroplating wastewater was performed using a mixture of two organophosphorus acidic extractants containing di-2,4,4-trimethylpentyl phosphinic acid (Cyanex 272) and di-2,4,4-trimethylpentyl mono-thio-phosphinic acid (Cyanex 302) in kerosene. The results showed almost 99±0.816% of Cr(VI) was synergistically reduced and extracted to the less toxic trivalent chromium (Cr(III)) using the total mixture concentration of 0.1 M (0.04 M Cyanex 272+0.06 M Cyanex 302). For recycling, the organic phase was recycled or reused up to 11 times for excellent extraction (99±0.471%) and stripping (99±0.942%) and became stable afterwards until a certain time. The total concentration of the mixture system was reduced by 50% (0.05 M) using 0.01 M Cyanex 272 and 0.04 M Cyanex 302, with almost 100% of Cr(VI) extraction as less toxic Cr(III). The Cr(III) in the loaded organic phase was completely recovered using 7.0 M hydrochloric acid (HCl). It is concluded that the synergistic extraction using Cyanex 272/Cyanex 302 system improved the Cr(VI) extraction and reduced the chemical consumption in the organic phase.

Synthesis of an arginine-functionalized polyaniline@FeOOH composite with high removal performance of hexavalent chromium ions from water: Adsorption behavior, regeneration and process capability studies

In this study, the synthesis of a novel arginine-functionalized polyaniline/FeOOH (Arg-PANI@FeOOH) composite for hazardous Hexavalent chromium ions (Cr(VI)) removal from wastewater was reported. The SEM, EDS, FTIR, XRD, and PZC measurements were used to characterize the as-developed Arg-PANI@FeOOH composite. Batch adsorption experiments were used to investigate the influence of pH, temperature, contact time, Arg-PANI@FeOOH amount, initial Cr(VI) concentration and coexisting ions on the efficiency of Cr(VI) removal. The Cr(VI) adsorption was much more advantageous at lower pH values, reflecting that the electrostatic interactions were the main driving forces that govern Cr(VI) binding mechanism on the Arg-PANI@FeOOH surface. The experimental data showed good fitness to the pseudo-second-order kinetics and Langmuir isotherm. The Cr(VI) species highest monolayer coverage capacity onto Arg-PANI@FeOOH was 682.30 mg g−1. The adsorption of Cr(VI) onto the Arg-PANI@FeOOH is spontaneous via an endothermic reaction. The competing anions were not affected the Cr(VI) adsorption, demonstrating that the Arg-PANI@FeOOH selectively adsorb Cr(VI) ions. The developed Arg-PANI@FeOOH material demonstrated good reusability up to five regeneration cycles. The process capability to predict the practical aptitude of Arg-PANI@FeOOH adsorbent to remove Cr(VI) from aqueous solutions was successfully applied. As a result, the adsorption of Cr(VI) onto Arg-PANI@FeOOH composite is a capable process for full-scale wastewater purification purposes. This paper provides relevant findings for a polyaniline-based adsorbent for the efficient removal of Cr(VI) from wastewater.

Feasibility study on a mini autonomous biosensor based on microbial fuel cell for monitoring hexavalent chromium in wastewater

SummaryMicrobial fuel cells (MFCs) are considered as power generation devices for sustainable energy. However, the power generated is insignificant compared to other energy production devices. In this study, a mini autonomous biosensor (MAB) based on MFCs has been designed for detecting hazardous hexavalent chromium in wastewater. Hexavalent chromium has been classified as a human carcinogen causing serious birth defects due to its mutagenic and teratogenic properties. The power generated by the MAB has been investigated to study the feasibility of providing power to itself. In addition, electrochemical analyses of conductive silver paste and carbon cloth as the anode were conducted in the MAB for detecting hexavalent chromium in the anode chamber. Results show that a maximum voltage of 518.17 mV and a power density of 1.075 mW/cm2 could be achieved using carbon cloth with an external resistance of 1000 Ω, while a higher limiting current density of 0.015 mA/cm2 could be achieved with conductive silver glue as the anode electrode. Besides, the voltage output of the MAB decreased rapidly with the addition of hexavalent chromium into the wastewater. Also, the recovery time for the MAB was much shorter than found in previous studies. The MAB demonstrated potential for simultaneous production of electricity and detection of hexavalent chromium, which would open up avenues for autosensing applications in the environment as well as smart powering devices. Results indicate that the MAB with conductive silver glue as anode electrode is feasible for detecting hexavalent chromium in wastewater.

Effect of Zinc Addition on Electrodeposition of Fe-W Alloys

Tungsten (W) and its alloys have been applied to various industrial fields for its excellent mechanical, tribological and chemical properties. Electrodeposition process is anticipated to be a economical and cost-effective method for preparing W-based alloys since W has the highest melting point among metals (3422 ℃). In general, electrodeposition of metal W from aqueous solution is difficult because it exists as oxyanions in a wide pH range. However, electrodeposition in the co-existence of iron group metals such as iron (Fe), nickel (Ni), and cobalt (Co), enables W to be reduced to metal state, which is so called the induced co-deposition. Recently, electrodeposited W alloys have gained increased attention due to their advanced properties such as high microhardness, thermal stability, wear resistance and corrosion resistance. Among them, binary Fe-W, Ni-W alloys have been most intensively studied. These alloys are expected to be promising substitute for hard chrome (Cr) plating due to its high hardness, abrasion resistance, heat resistance and corrosion resistance without the use of hazardous hexavalent chromium (Cr6+). Meanwhile, Ni has been reported as the one of the major elements in triggering skin allergies for humans. Therefore, we focused on Fe-W-based alloys that do not use Ni. Unfortunately, Fe-W alloys are reported to have inferior mechanical properties and corrosion resistance compared to Ni-W alloys. Thus, the addition of Zinc (Zn); an element that is widely used in anti-corrosion coatings, as a third element to the Fe-W binary alloy was considered for preparation of a ternary alloy with improved properties.This study reports the first experimental results of electrodeposition of ternary Fe-W-Zn alloy by incorporation of Zn to Fe-W alloys. Ternary Fe-W-Zn plating was prepared in citrate-ammonia aqueous solution heated to 80℃ by potentiostatic elcecrolysis range from -1.1 to -1.4V (vs. Ag/AgCl). Ternary alloys with the compositions of Fe-(28.8 to 37.1 at.%) W-(1.7 to 6.5 at.%) Zn were obtained with maximum current efficiency of 42%. The corrosion properties of the prepared ternary alloys were compared with those of Ni-W and Fe-W platings by a potentiodynamic polarization test in deaerated 1M sulfuric acid solution and 3 mass% sodium chloride solution. Although Zn has lower potential than Fe, ternary Fe-W-Zn alloys with relatively low Zn contents of 1.7 to 2.6 at.% showed better anti-corrosion properties than Ni-20 at.%W and Fe-33 at.%W alloys in acidic media. Addition of a small amount of Zn was found to be effective in tuning properties of Fe-W alloys. Acknowledgement This work was partially supported by the JST-OPERA Program, Japan [grant number JPMJOP1843]

Facile synthesis and characterization of a novel 1,2,4,5-benzene tetracarboxylic acid doped polyaniline@zinc phosphate nanocomposite for highly efficient removal of hazardous hexavalent chromium ions from water

The present study describes the preparation of a novel 1,2,4,5-benzene tetracarboxylic acid doped polyaniline@zinc phosphate (BTCA-PANI@ZnP) nanocomposite via a facile two-step procedure. Thereafter, the as-prepared composite material adsorption characteristics for Cr(VI) ions removal were evaluated under batch adsorption. Kinetic approach studies for Cr(VI) removal, clearly demonstrated that the results of the adsorption process followed the pseudo second order and Langmuir models. The thermodynamic study indicated a spontaneous and endothermic process. Furthermore, higher monolayer adsorption was determined to be 933.88 mg g−1. In addition, the capability study regarding Cr(VI) ions adsorption over BTCA-PANI@ZnP nanocomposite clearly revealed that our method is suitable for large scale application. X-ray photoelectron spectroscopy (XPS) analysis confirmed Cr(VI) adsorption on the BTCA-PANI@ZnP surface, followed by its subsequent reduction to Cr(III). Thus, the occurrence of external mass transfer, electrostatic attraction and reduction phenomenon were considered as main mechanistic pathways of Cr(VI) ions removal. The superior adsorption performance of the material, the multi-dimensional characteristics of the surface and the involvement of multiple removal mechanisms clearly demonstrated the potential applicability of the BTCA-PANI@ZnP material as an effective alternative for the removal of Cr(VI) ions from wastewater.

Integration of Cynodon dactylon and Muraya koenigii plant extracts in amino-functionalised silica-coated magnetic nanoparticle as an effective sorbent for the removal of chromium(VI) metal pollutants.

Immobilised magnetic nanoparticles are extensively used owing to their superparamagnetic nature, surface interaction, and binding specificity with the appropriate portentous substances. The present research focuses on the development of a portentous, robust carrier, which integrates the silica-coated amino-functionalised magnetic nanoparticle (AF-MnP) with the plant extracts of Cynodon dactylon (L1) and Muraya koenigii (L2) for the stable and enhanced removal of hazardous hexavalent chromium pollutant in the wastewater. Vibrating sample magnetometer (Ms - 45 emu/g) determines the superparamagnetic properties; Fourier-transform infrared spectroscopy determines the presence of functional groups such as NH2, Si-O-Si, C=C; high-resolution transmission electron microscopy, field emission scanning electron microscope and energy-dispersive X-ray spectroscopy determine the size of the green adsorbents in the range of 20 nm and the presence of elements such as Fe, N, and Si determines the efficacy of the synthesised silica-coated AF-MnP. The AF-MnP-L1 shows the maximum adsorption capacity of 34.7 mg/g of sorbent calculated from the Langmuir isotherm model and the process follows pseudo-second-order kinetics. After treatment, the adsorbents can be easily separated from the solution in the presence of an external magnetic field and are reused for nine cycles after acid treatment with the minimal loss of adsorption efficiency.