3D-printing of Fe-Ni bimetallic particles and their application in removal of arsenic from water

Arsenic is a hazardous element found in water sources, and removing it is crucial for ensuring a safe environment and water quality. Iron-based metal oxides efficiently remove arsenic; however, their small particle sizes make separation from water difficult after arsenic removal. Furthermore, the growing global issue of polymer waste further complicates environmental concerns. Combining three-dimensional (3D) printing and adsorption technology by incorporating nanosized functional materials into supporting polymers offers a potential solution to address both challenges. In this study, we developed a 3D-printed adsorption material through the incorporation of synthesized Fe-Ni bimetallic particles into a supporting polymer using selective laser sintering (SLS) technology. This adsorbent's properties were examined through scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR), and zeta potential. Furthermore, its performance in removing As(III) and As(V), even at trace levels, was assessed under varied conditions. The 3D-printed adsorbent demonstrated excellent removal of As(III) at pH 6, and As(V) at pH 4, lowering their concentration below 10 μg/L, thereby adhering to the limit established by the World Health Organization (WHO). Both As(III) and As(V) fitted the Freundlich isotherm and pseudo-second-order model, suggesting potential heterogeneous and chemisorption processes. FT-IR indicated that the exchange of the -OH group of Fe-OH with oxyanions of As(III) and As(V) could be the adsorption mechanism. Additionally, thermodynamic evaluation unveiled an endothermic and non-spontaneous adsorption reaction. The 3D-printed adsorbent exhibited excellent reusability across recurring adsorption cycles. The combination of SLS 3D printing with Fe-Ni bimetallic particles produces structures that retain their functionality in removing both arsenic species present in water. This indicates the potential of the 3D-printed adsorbent for effective treatment of arsenic-contaminated water, offering remedies to challenges like handling small particle sizes, mitigating polymer waste, and addressing environmental concerns.

Adsorption of Copper and Arsenic from Water Using a Semi-Interpenetrating Polymer Network Based on Alginate and Chitosan

New biobased hydrogels were prepared via a semi-interpenetrating polymer network (semi-IPN) using polyacrylamide/chitosan (PAAM/chitosan) hydrogel for the adsorption of As(V) or poly acrylic acid/alginate (PAA/alginate) hydrogel for the adsorption of Cu(II). Both systems were crosslinked using N,N'-methylenebisacrylamide as the crosslinker and ammonium persulfate as the initiating agent. The hydrogels were characterized by SEM, Z-potential, and FTIR. Their performance was studied under different variables, such as the biopolymer effect, adsorbent dose, pH, contact time, and concentration of metal ions. The characterization of hydrogels revealed the morphology of the material, with and without biopolymers. In both cases, the added biopolymer provided porosity and cavities' formation, which improved the removal capacity. The Z-potential informed the surface charge of hydrogels, and the addition of biopolymers modified it, which explains the further metal removal ability. The FTIR spectra showed the functional groups of the hydrogels, confirming its chemical structure. In addition, the adsorption results showed that PAAM/chitosan can efficiently remove arsenic, reaching a capacity of 17.8 mg/g at pH 5.0, and it can also be regenerated by HNO3 for six cycles. On the other hand, copper-ion absorption was studied on PAA/alginate, which can remove with an adsorption capacity of 63.59 mg/g at pH 4.0, and the results indicate that it can also be regenerated by HNO3 for five cycles.

A review on multi-synergistic transition metal oxide systems towards arsenic treatment: Near molecular analysis of surface-complexation (synchrotron studies/modeling tools)

The science and interface chemistry between the arsenic (As) anions and the different adsorbent systems have been gaining interest in recent years in environmental remediation applications. Metal-oxides and the corresponding hybrid systems have shown promising performance as novel adsorbents in various treatment technologies. The abundance, surface chemistry, high surface area (active-centres), various synthesis and functionalization methodologies, and good recyclability make these metal oxide-based nanomaterials as potential remediating agents for As oxyanions. This work critically reviews eight different platforms focused on the arsenic contamination issue, where the first classification describes the origin of arsenic contamination and presents geographical and demo-graphical considerations. The following section briefs the state-of-the-art remediation techniques for arsenic treatment with a comparative evaluation. An emphasized discussion has been provided regarding the adsorption and classification of various metal oxide adsorbents. In the next classification, various multi-synergism abilities like Redox activity, Surface functional groups, Surface area/morphology, Heterogeneous catalysis, Reactive oxygen species, Photo-catalytic/electro-catalytic reactions, and Electrosorption are detailed. The classification of various characterization tools for accessing the arsenic remediation qualitatively and quantitatively are given in the fifth chapter. The first-of-its-kind dedicated analysis has been given on the surface complexation aspects of the arsenic speciation onto various metal adsorbent systems using synchrotron results, surface-complexation modeling, and molecular simulation (e.g., DFT) in the sixth chapter. The current sensing applications of these novel nano-material systems for arsenic determination using colorimetric and electrochemical-based analytical tools and a note about the economic parameters, i.e., regeneration aspects of various adsorbent systems/the sustainable applications of the treated sludge materials, are provided in the final sections. This work makes a critical analysis of 'Environmental Nanotechnology' towards 'Arsenic Treatment'.

Anti-bacterial and arsenic remediation insights in aqueous systems onto heterogeneous metal oxide (Cu0.52Al0.1Fe0.47O4)/rGO hybrid: an approach towards airborne microbial degradation

Copper-based ternary metal oxide (i.e., Cu0.52Al0.01Fe0.47O4) impregnated reduced graphene oxide nanohybrid is verified for microbial and arsenic treatment. Growth inhibition of colonies are observed around 99.99% (E. coli), and 99.83% (S. aureus) at 10-20 μg/mL of hybrid dosage, respectively. The inhibition rates for both the colonies are increased to 99.9998% at 80 μg/mL. TEM images have shown insight of cell-content/lipid leakage behavior after inoculating with the hybrid. The efficient hindrance towards microbial colony growth is attributed to better charge transfer, reactive oxygen species generation, and metal-ion release. Maximum arsenic sorption capacities are observed around 248 and 314 mg/g for As(III), and As(V), respectively (C_i ~ 500 ppm). Surface morphology studies onto arsenic adsorption are reported with atomic force microscope, and FT-IR/Raman analysis. A detailed discussion onto individual spectra of As 3d spectra confirmed the occurrence of redox transformation in arsenic species [As(III)]. The variation in the quantity (at. %) of oxygen functional groups in O1s spectra (i.e., M-O, M-OH, and -OH₂) onto the hybrid supported the ligand-exchange behavior. Cyclic voltammetry study in arsenic electrolytes (10 µM - 1 mM) provides the occurrence of various in-situ electrochemical reactions supporting the redox activity. A significant electromagnetic wave absorption characteristics of the present hybrid is proposed with plausible airborne antimicrobial-agent abilities.

Defects induced by Al substitution enhance As(V) adsorption on ferrihydrites

An original rationale is proposed to explain the controversial role of aluminum, a common substitutive element in ferrihydrite (Fh), on arsenic adsorption. The adsorption of arsenic on synthetic Al-for-Fe substituted Fh (AlFh) with up to 20 mol% Al was investigated at pH 5 and 8. The reduced interplanar spacings observed by selected area electron diffraction show that all AlFh samples are isomorphically substituted up to 20 mol% Al. A 15 mol% Al incorporation increases the arsenic uptake by 28%. In contrast, the Langmuir binding constants decrease, suggesting weaker bonds. Arsenic uptake reduces by 50% as pH rises from 5 to 8. The Al-for-Fe substitution in ferrihydrite causes structural defects, proton-compensated by OH groups, as indicated by the Vegard rule deviation. X-ray photoelectron spectroscopy demonstrates the increase in the relative amount of surface M-OH sites (45% to 77%) with Al concentration (AlFh-0 to AlFh-20), respectively. The enhanced As(V) uptake was ascribed to the insertion of hydroxyls on the Fh structural defects. Fourier-transformed-infrared spectroscopy showed that the sites modified by Al introduction are involved in As adsorption. These findings help to understand aluminum's role in arsenic adsorption, fixation, and fate in the environment.

Mechanism of Cd(II) and Cu(II) Adsorption onto Few-Layered Magnetic Graphene Oxide as an Efficient Adsorbent

Heavy metal contamination caused by industrial discharge is a challenging environmental issue. Herein, an efficient adsorbent based on few-layered magnetic graphene oxide (FLMGO) was fabricated, characterized, and utilized to remove aqueous Cd(II) and Cu(II). Results present that the two components graphene oxide (GO) and Fe₃O₄ of FLMGO promote mutually, enabling FLMGO to outperform either GO or Fe₃O₄. Specifically, FLMGO adsorbs Cd(II) and Cu(II) with adsorption quantities of 401.14 and 1114.22 mg·g^-1 in 5 and 7 min, respectively. Moreover, FLMGO can be readily recovered via magnetic separation using a hand-held magnet. Adsorptions are spontaneous, endothermic, and entropy increasing, which are the best described by the Freundlich and pseudo-second-order model. The interaction mechanism is as follows: lone pair electrons in C=O- and C-O-related groups were coordinated toward Cd(II) and Cu(II) to induce chemical interaction. The high adsorption efficiency endows FLMGO with encouraging application potential in heavy metal remediation.

Insights of arsenic (III/V) adsorption and electrosorption mechanism onto multi synergistic (redox-photoelectrochemical-ROS) aluminum substituted copper ferrite impregnated rGO

The understanding of mechanistic insights in environmental remediation and mitigation systems is attracting larger attention, in recent days. Here in, aluminium substituted copper ferrite impregnated rGO hybrid (CAF-rGO) is verified to understand the adsorption/electrosorption mechanism of arsenic in aqueous systems. Near-surface study (XPS: As 3d, Cu 2p, Fe 2p, Al 2p, O 1s, C 1s) proposes redox, and ligand exchange reactions between contaminant, and CAF-rGO. Adsorption capacities are observed around 128.8 mg g^-1 [As(III)], 153.5 mg g^-1 [As(V)] with Freundlich model isotherms. Kinetics study follows the PSO model with influence of solar light (> 420 nm). Cyclic voltammetry (CV) analysis in different molarity conditions observed with signals around +0.1 and -0.6 V confirm the redox abilities, and N₂/O₂ purged environments understood that electrosorption occurred through both reduction and sorption. Electrosorption study with pH variation shows the effect of protonation on the redox activity of individual arsenic species. Consistent signal around -0.6 ± 0.05 V in all the CV plots (i.e., Molarity, Environment, pH) recommends the usage of CAF-rGO for arsenic mitigation. Possible influence of photo-current (∼40 μA/cm² at ∼ 0 V) towards As(III/V) decontamination is understood though photoelectrochemical analysis. Impedance plot shows low-resistance and better diffusion of arsenic oxy-anions during light irradiation. Synergistic nature of CAF-rGO generates reactive oxygen species (i.e., ^●OH/^●O₂^-/₁O²) in mitigating highly toxic As(III) species is also detailed in the present work.

As(III) removal from aqueous solution by katoite (Ca3Al2(OH)12)

As (III) is widely distributed in groundwater which is relatively harder to be removed comparing to As (V). Co-grinding Ca(OH)₂ with Al(OH)₃ was conducted to manufacture katoite (Ca₃Al₂(OH)₁₂) for the complete removal of As(III) (concentration below drinking water standard of WHO (<10 ppb)) during one-step agitation operation. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TG), and X-ray photoelectron spectroscopy (XPS) were applied for the illustration of adsorption mechanism. Katoite could intercalate As(III) into the layered space forming arsenite pillared Ca-Al layered double hydroxide (LDH). The coexisting anions such as Cl^-, SO₄^2-, and NO₃^- had minor effects on As (III) removal performance using katoite. Techno-economic analysis demonstrated the feasibility of large-scale katoite production and its practical application for As(III) polluted groundwater purification, especially in the undeveloped areas where groundwater was used as irrigation and drinking water.

Synthesis of amino-functionalized biochar/spinel ferrite magnetic composites for low-cost and efficient elimination of Ni(II) from wastewater

Novel amino-modified rice bran biochar/MgFeAlO₄ (RB@MgFeAlO₄-NH₂) magnetic composites were synthesized via a simple one-step solvothermal approach and applied for removing toxic Ni(II) from wastewater. The elimination process and sorption performance of Ni(II) on RB@MgFeAlO₄-NH₂ were analyzed by combining batch experiments and spectral techniques. The sorption isotherms and kinetic data indicated that Ni(II) sorption on RB@MgFeAlO₄-NH₂ was monolayer and rapid. The experimental results confirmed that the obtained RB@MgFeAlO₄-NH₂ magnetic composite had high sorption capacity for Ni(II). The maximum sorption capacity of Ni(II) on RB@MgFeAlO₄-NH₂ was 201.62 mg g^-1. The researches based on the sorption mechanism showed that the ion exchange mechanism accounted for 76.51% of Ni(II) sorption. In addition, the amino, carboxyl and hydroxyl functional groups were also involved in the complexation with Ni(II). In view of its multiple advantages of environmental friendliness, low cost, easy magnetic separation and high sorption capacity, RB@MgFeAlO₄-NH₂ will be an excellent adsorbent for low-cost and efficient elimination of Ni(II) from aqueous solutions.

Fe3O4-Functionalized Boron Nitride Nanosheets as Novel Adsorbents for Removal of Arsenic(III) from Contaminated Water

We report the application of Fe3O4-functionalized boron nitride nanosheets (BNNS-Fe3O4 nanocomposite) for the remediation of As(III) ions from contaminated water. The specific surface area of the nanocomposite has been found as 179.5 m2 g-1. Due to its superparamagnetic nature at room temperature, the nanocomposite can be easily isolated from the solution under an external magnetic field. For As(III) ions, the maximum adsorption capacity of the nanocomposite is obtained as 30.3 mg g-1, which is approximately 4 times more than that of the bare BNNSs (8.5 mg g-1). The results from density functional theory calculations are also in close agreement with experimental findings and show that As(OH)3 binds more (∼4 times) efficiently to the BNNS-Fe3O4 nanocomposite than the bare BNNSs, implying a 4 times higher adsorption capacity of the nanocomposite. Especially, it is found that the synthesized nanocomposite could lessen the concentration of As(III) ions from 134 to 2.67 ppb in a solution at 25 °C. On increasing the temperature to 35 °C, the level of As(III) ions could be reduced from 556 to 10.29 ppb, which is close to the limit prescribed by the World Health Organization. The adsorbent was easily separable and showed regeneration properties. These outcomes depict the prospect of using BNNS-Fe3O4 nanocomposites as commercial adsorbents for the removal of As(III) ions from contaminated water.

Facile inverse micelle fabrication of magnetic ordered mesoporous iron cerium bimetal oxides with excellent performance for arsenic removal from water

In this study, magnetic ordered mesoporous Fe/Ce bimetal oxides (OMICs) were successfully synthesized via the modified sol-gel-based inverse micelle method. The textural/structure properties, surface chemistry and adsorption behavior of OMICs could be easily adjusted by using the calcination temperature. The sintering of samples would decrease the surface area, while expand the pore and crystallite size, which resulted in the formation of highly ordered inner-connected structure. Compared with pure mesoporous iron oxides (MI) and mesoporous cerium oxides (MC), this ordered mesoporous iron-cerium bimetal oxides (OMIC-3, 450 °C) exhibited remarkable arsenic adsorption performance. The maximum adsorption capacities of As(III) and As(V) for OMIC-3 were 281.34 and 216.72 mg/g, respectively, and both As(III)/As(V) adsorption kinetics were well described by the pseudo-second order. The ionic strength and coexisting ions (except SiO₃^2- and PO₄^3-) did not affect arsenic removal, while humic acid (HA) significantly influenced on the arsenic removal even at a lower concentration. The adsorption mechanism study revealed that both the surface charge and surface M-OH groups of OMIC-3 were played the key roles in arsenic removal. The reusable property suggested that this magnetic OMIC-3 was a promising excellent adsorbent for decontamination of arsenic-polluted (especially As(III)-polluted) wastewater.

Magnetite-Coated Boron Nitride Nanosheets for the Removal of Arsenic(V) from Water

It is widely known that the existence of arsenic (As) in water negatively affects humans and the environment. We report the synthesis, characterization, and application of boron nitride nanosheets (BNNSs) and Fe₃O₄-functionalized BNNS (BNNS-Fe₃O₄) nanocomposite for removal of As(V) ions from aqueous systems. The morphology, surface properties, and compositions of synthesized nanomaterials were examined using scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction, surface area analysis, zero-point charge, and magnetic moment determination. The BNNS-Fe₃O₄ nanocomposites have a specific surface area of 119 m² g^-1 and a high saturation magnetization of 49.19 emu g^-1. Due to this strong magnetic property at room temperature, BNNS-Fe₃O₄ can be easily separated in solution by applying an external magnetic field. From the activation energies, it was found that the adsorption of As(V) ions on BNNSs and BNNS-Fe₃O₄ was due to physical and chemical adsorption, respectively. The maximum adsorption capacity of BNNS-Fe₃O₄ nanocomposite for As(V) ions has been found to be 26.3 mg g^-1, which is 5 times higher than that of unmodified BNNSs (5.3 mg g^-1). This closely matches density functional theory simulations, where it is found that binding energies between BNNS-Fe₃O₄ nanocomposite and As(OH)₅ are 5 times higher than those between BNNSs and As(OH)₅, implying 5 times higher adsorption capacity of BNNS-Fe₃O₄ nanocomposite than unmodified BNNSs. More importantly, it was observed that the synthesized BNNS-Fe₃O₄ nanocomposite could reduce As(V) ion concentration from 856 ppb in a solution to below 10 ppb (>98.83% removal), which is the permissible limit according to World Health Organization recommendations. Finally, the synthesized adsorbent showed both separation and regeneration properties. These findings demonstrate the potential of BNNS-Fe₃O₄ nanocomposite for commercial application in separation of As(V) ions from potable and waste water streams.

Redox synergistic Mn-Al-Fe and Cu-Al-Fe ternary metal oxide nano adsorbents for arsenic remediation with environmentally stable As(0) formation

Arsenic mitigation behavior in aqueous systems is being evaluated for Mn-Al-Fe, Cu-Al-Fe nano adsorbents. Morphological, and vibrational spectroscopy analysis are observed with As-OH, and As-O surface complexes. XPS study of individual As(3d) spectra at different parameters is observed with multiplet peak behavior attributed to redox behavior of Mn-Al-Fe, Cu-Al-Fe. Significant proportions of As(0) signal (∼25 at.% in pH 7, ∼78 at.% in pH 2, ∼58 at.% in pH 12) implicate an environmentally stable behavior of these adsorbents to address the arsenic leaching issue. Adsorption kinetics are observed with Pseudo Second Order (PSO) model, and Freundlich model supported multilayer adsorption behavior is observed for adsorption isotherms. Trace metal voltammetry studies are observed with 75-90 % of As(III) mitigation in aliquot samples. Detailed study of Mn(2p), Cu(2p), Fe(2p), and O(1 s) spectra explains redox active, and surface ligand exchange synergism in arsenic adsorption. Low equilibrium concentrations (Ce < 10 ppb) in As(V) systems (C_i ∼ 100 and 500 ppb) indicate the drinking water application of these systems. Cyclic-voltammetry (CV) studies implicate the mitigation and immobilization of arsenic species onto adsorbent by both reduction, and sorption phenomenon.

Arsenic surface complexation behavior in aqueous systems onto Al substituted Ni, Co, Mn, and Cu based ferrite nano adsorbents

The present study is about surface complexation behavior of arsenic species adsorbed onto ternary metal oxide adsorbents (Ni-Al-Fe, Co-Al-Fe, Mn-Al-Fe, and Cu-Al-Fe). The analysis is carried out by X-ray absorption spectroscopy (XAS) tool. XANES (μ(E) vs. E) spectra close to the absorption edge (i.e., As K-edge) of all samples are observed along with the As(III) and As(V) standards. The first derivative of XANES for Ni-As(V), and Cu-As(V) samples agree with that of As(V) standards, respectively. Whereas, As(III) adsorbed adsorbent systems (i.e., Ni, Co, Mn, and Cu) are observed with mixed oxidation state of arsenic. A total of 65-85 % is observed with initial oxidation state (As(III) or As(V)), and remaining 15-35 % is observed with modified oxidation state (As(V) or As(III)) that explains the occurrence of possible charge transfer. EXAFS analysis shows the As-O bond distances in the range of 1.7-1.8 Å. The corresponding As-M bond distances are around 2.7, 3.2, and 3.6 Å which confirms the formation various edge sharing (²E), and corner sharing (²C, ¹V) surface complexes. Surface coverage is understood as an important parameter as bidentate attachments (²E, ²C) are evident in As(III), and As(V), but monodentate attachments (¹V) are only observed in As(V).

Efficient removal of pentachlorophenol from aqueous solution by 4-tert-butylcalix[8]arene modified thermally sensitive hydrogels

We prepared poly(N-isopropylacrylamide-co-4-tert-butylcalix[8]arene) (PNIPAM-TBCX) hydrogels by copolymerization of N-isopropylacrylamide (NIPAM) with 4-tert-butylcalix[8]arene (TBCX) to capture hazardous pentachlorophenol (PCP) from aqueous solution. Adsorption experiments showed that the adsorption capacities of PNIPAM-TBCX hydrogels reached 1.96, 2.08 and 2.02 mg PCP per 1 g of hydrogel, while the molar percentage ratio of TBCX in the hydrogels was as low as 0.5%, 0.7% and 1%. The equilibrium adsorption of PCP on the hydrogels was studied using different adsorption models. In addition, the PNIPAM-TBCX hydrogel still retained its performance when regenerated several times by immersing in water at 323 K.

We synthesized 4-tert-butylcalix[8]arene modified poly(N-isopropylacrylamide) hydrogels to enhance the adsorption ability for pentachlorophenol in aqueous solutions.

Aluminum Substituted Cobalt Ferrite (Co-Al-Fe) Nano Adsorbent for Arsenic Adsorption in Aqueous Systems and Detailed Redox Behavior Study with XPS

Arsenic [As(III) and As(V)] adsorption on aluminum substituted cobalt ferrite (Co-Al-Fe) ternary metal oxide adsorbent is reported by means of qualitative and quantitative spectroscopy tools. IR and Raman active signals were observed around 810-920 cm^-1 band indicate different As-OH_complexed and As-O_uncomplexed stretching vibrations on to the adsorbent. The adsorption behavior of arsenic (III and V) onto these adsorbents is studied as a function of contact time, different concentrations, and pH conditions. The kinetics study on adsorption were performed to understand nature of adsorption which supports the Pseudo Second Order (PSO) model. The adsorption isotherms study indicates Freundlich type of adsorption. The maximum adsorption capacity of Co-Al-Fe adsorbent is observed around 130 and 76 mg g^-1 for As(III) and As(V) systems, respectively. Detailed XPS study of As 3d, Fe 2p, Co 2p, and O 1s spectra has been reported in explaining the redox behavior and ligand exchange reactions in supporting arsenic adsorption mechanism.