Determination of arsenic(III) and arsenic(V) binding to microwave assisted hydrothermal synthetically prepared Fe3O4, Mn3O4, and MnFe2O4 nanoadsorbents

Nanotechnology in Agriculture: Manganese Ferrite Nanoparticles as a Micronutrient Fertilizer for Wheat

Limited research has focused on nanoparticle (NP) applications' impact on edible wheat parts in a field environment. Here, we studied the nutritional quality of edible parts of wheat (Triticum aestivum L.) with a field experiment by spraying MnFe2O4 nanoparticles. Wheat was foliar sprayed with 0, 25, 50, and 100 mg/L composite manganese ferrite (MnFe2O4) NPs during 220 d of a growth period. Ionic controls were prepared using the conventional counterparts (MnSO4·H2O and FeSO4·7H2O) to compare with the 100 mg/L MnFe2O4 NPs. After three consecutive foliar applications, nanoparticles demonstrated a substantial elevation in grain yield and harvest index, exhibiting a noteworthy increase to 5.0 ± 0.12 t/ha and 0.46 ± 0.001 in the 100 mg/L NP dose, respectively, concomitant with a 14% enhancement in the grain number per spike. Fe, Mn, and Ca content in grain increased to 77 ± 2.7 mg/kg, 119 ± 2.8 mg/kg, and 0.32 ± 7.9 g/kg in the 100 mg/L NPs, respectively. Compared to the ion treatment, the 100 mg/L NP treatments notably boosts wheat grain crude protein content (from 13 ± 0.79% to 15 ± 0.58%) and effectively lowers PA/Fe levels (from 11 ± 0.7 to 9.3 ± 0.5), thereby improving Fe bioavailability. The VSM results exhibited a slight superparamagnetic behavior, whereas the grains and stems exhibited diamagnetic behavior. The results indicate that the nanomaterial did not accumulate in the grains, suggesting its suitability as an Fe and Mn-rich fertilizer in agriculture. Above all, the foliar application of nanocomposites increased the concentrations of Fe, Mn, and Ca in wheat grains, accompanied by a significant enhancement in grain yield. Therefore, the research results indicate that the foliar application of MnFe2O4 NPs can positively regulate wheat grains' nutritional quality and yield.

Removal of As(V) from aqueous solution using modified Fe3O4 nanoparticles

The removal of arsenic contamination from the aqueous environment is of great importance in the conservation of the Earth's water resources, and surfactants are a promising material used to modify magnetic nanoparticles to improve adsorption properties. Therefore, it is important to develop efficient and selective adsorbents for arsenic. Surface modification of Fe₃O₄ was carried out using anionic, cationic and zwitterionic surfactants to obtain composite Fe₃O₄@SDS, Fe₃O₄@CTAB, Fe₃O₄@SNC 16 and Fe₃O₄@NPC 16 (collectively referred to as Fe₃O₄@surfactants). The synthesized composite Fe₃O₄@surfactants magnetic nanoparticles were characterized by XRD, TEM and FTIR. The As(V) removal characteristics of the composite magnetic nanoparticles from the aqueous solution were evaluated by adsorption batch experiments which indicated the possibility of effective application of the surfactant-modified Fe₃O₄ magnetic nanoparticles for the removal of As(V) from aqueous solution. The adsorption equilibrium of the composites was reached in 30 min and the kinetic data followed the pseudo-second-order model. Langmuir equation could represent the adsorption isotherm data very well. Moreover, under the identical conditions, Fe₃O₄@CTAB showed maximum capacity of adsorption for As(V) (55.671 mg g^-1), with its removal efficiency being much higher than that of the other composites. In addition, the Fe₃O₄@surfactants composite magnetic nanoparticles retained 93.5% of its initial arsenic removal efficiency even after re-using it five times. The mechanism of arsenic adsorption by Fe₃O₄@surfactants composite magnetic nanoparticles was proved to be complexation via electrostatic attraction, which was mainly innersphere in nature.

Effects of cobalt doping on the reactivity of hausmannite for As(III) oxidation and As(V) adsorption

Hausmannite is a common low valence Mn oxide mineral, with a distorted spinel structure, in surficial sediments. Although natural Mn oxides often contain various impurities of transitional metals (TMs), few studies have addressed the effect and related mechanism of TM doping on the reactivity of hausmannite with metal pollutants. Here, the reactivity of cobalt (Co) doped hausmannite with aqueous As(III) and As(V) was studied. Co doping decreased the point of zero charge of hausmannite and its adsorption capacity for As(V). Despite a reduction of the initial As(III) oxidation rate, Co-doped hausmannite could effectively oxidize As(III) to As(V), followed by the adsorption and fixation of a large amount of As(V) on the mineral surface. Arsenic K-edge EXAFS analysis of the samples after As(V) adsorption and As(III) oxidation revealed that only As(V) was adsorbed on the mineral surface, with an average As-Mn distance of 3.25-3.30 Å, indicating the formation of bidentate binuclear complexes. These results provide new insights into the interaction mechanism between TMs and low valence Mn oxides and their effect on the geochemical behaviors of metal pollutants.

Photocatalytic dye degradation using nickel ferrite spinel and its nanocomposite

Coloured wastewater is a major issue of today for human health and ecology. Among all available processes such as physical, chemical, biological and electrochemical methods, photocatalysis can be a promising solution because of its ability to degrade colour-causing compounds completely by converting them into simpler molecules (H₂O, CO₂) depending on dye structure. In this work, NiFe₂O₄ was synthesized by the co-precipitation method. Furthermore, the composites of NiFe₂O₄ with TiO₂ were synthesized by varying amounts of TiO₂. The spinel and composites were characterized by XRD, ZETA analysis and UV-DRS. Their photocatalytic activities were investigated using the photocatalytic degradation of reactive turquoise blue 21 (RB 21) dye as model pollutants under sunlight. The increased absorption of the visible light and the enhanced separation of the electron-hole pairs due to the relative energy band positions in NiFe₂O₄ and TiO₂ are considered as the main advantages. Our results showed that NiFe₂O₄-based nanocomposites could be used as an effective and magnetic retrievable photocatalyst.

Nanomaterials photocatalytic activities for waste water treatment: a review

Water is necessary for the survival of life on Earth. A wide range of pollutants has contaminated water resources in the last few decades. The presence of contaminants incredibly different dyes in waste, potable, and surface water is hazardous to environmental and human health. Different types of dyes are the principal contaminants in water that need sudden attention because of their widespread domestic and industrial use. The toxic effects of these dyes and their ability to resist traditional water treatment procedures have inspired the researcher to develop an eco-friendly method that could effectively and efficiently degrade these toxic contaminants. Here, in this review, we explored the effective and economical methods of metal-based nanomaterials photocatalytic degradation for successfully removing dyes from wastewater. This study provides a tool for protecting the environment and human health. In addition, the insights into the transformation of solar energy for photocatalytic reduction of toxic metal ions and photocatalytic degradation of dyes contaminated wastewater will open a gate for water treatment research. The mechanism of photocatalytic degradation and the parameters that affect the photocatalytic activities of various photocatalysts have also been reported.

Tomato Fruit Nutritional Quality Is Altered by the Foliar Application of Various Metal Oxide Nanomaterials

Carbohydrates and phytonutrients play important roles in tomato fruit’s nutritional quality. In the current study, Fe₃O₄, MnFe₂O₄, ZnFe₂O₄, Zn_0.5Mn_0.5Fe₂O₄, Mn₃O₄, and ZnO nanomaterials (NMs) were synthesized, characterized, and applied at 250 mg/L to tomato plants via foliar application to investigate their effects on the nutritional quality of tomato fruits. The plant growth cycle was conducted for a total of 135 days in a greenhouse and the tomato fruits were harvested as they ripened. The lycopene content was initially reduced at 0 stored days by MnFe₂O₄, ZnFe₂O₄, and Zn_0.5Mn_0.5Fe₂O₄; however, after a 15-day storage, there was no statistical difference between the treatments and the control. Moreover, the β-carotene content was also reduced by Zn_0.5Mn_0.5Fe₂O₄, Mn₃O₄, and ZnO. The effects of the Mn₃O₄ and ZnO carried over and inhibited the β-carotene after the fruit was stored. However, the total phenolic compounds were increased by ZnFe₂O₄, Zn_0.5Mn_0.5Fe₂O₄, and ZnO after 15 days of storage. Additionally, the sugar content in the fruit was enhanced by 118% and 111% when plants were exposed to Mn₃O₄ and ZnO, respectively. This study demonstrates both beneficial and detrimental effects of various NMs on tomato fruit quality and highlights the need for caution in such nanoscale applications during crop growth.

Molecular Mechanisms of Early Flowering in Tomatoes Induced by Manganese Ferrite (MnFe2O4) Nanomaterials

Nanomaterials (NMs) have demonstrated enormous potential to improve agricultural production. Ten mg L^-1 of customized manganese ferrite (MnFe₂O₄) NMs was selected as the optimal dose based on its outstanding effects on promoting tomato flowering and production. After the foliar application before flowering, MnFe₂O₄ NMs increased the leaf chlorophyll content by 20 percent, and significantly upregulated the expressions of ferredoxin, PsaA, and PsbA in leaves, likely by serving as an electron donor, leading to a significant increase in photosynthesis efficiency by 13.3%. Long distance transport of sucrose was then confirmed by the upregulation of sucrose transporter SUT1 and SUT2 in NM-treated leaves and meristems. The genes associated with gibberellin biosynthesis, including GA20ox2, GA20ox3, and SIGAST, and a flowering induction gene SFT, were also significantly upregulated. Importantly, the flowering time was 13 days earlier by MnFe₂O₄ NMs over the control. At the reproductive stage, MnFe₂O₄ NMs increased pollen activity and ovule size, leading to the significant increase in fruit number per plant, single fruit weight, and fruit weight per plant by 50%, 30%, and 75%, respectively. Metabolically, a significant increase of glucose-6-phosphate, phenylalanine, rutin, and ascorbic acid (vitamin C), as well as a significant decrease of tomatine and methionine, demonstrates an increased nutritional value of the tomato fruits. A verified companion field experiment showed an increase of 84.1% in total tomato production with the MnFe₂O₄ NM amendment. These findings provide support for the early flowering and yield improvement in nano-enabled agricultural systems.

Geogenic arsenic removal through core-shell based functionalized nanoparticles: Groundwater in-situ treatment perspective in the post-COVID anthropocene

Groundwater, one of the significant potable water resources of the geological epoch is certainly contaminated with class I human carcinogenic metalloid of pnictogen family which delimiting its usability for human consumption. Hence, this study concerns with the elimination of arsenate (As(V)) from groundwater using bilayer-oleic coated iron-oxide nanoparticles (bilayer-OA@FeO NPs). The functionalized (with high-affinity carboxyl groups) adsorbent was characterized using the state-of-the-art techniques in order to understand the structural arrangement. The major emphasis was to examine the effects of pH (5.0-13), contact times (0-120 min), initial concentrations (10-150 μg L^-1), adsorbent dosages (0.1-3 g L^-1), and co-existing anions in order to understand the optimal experimental conditions for the effective removal process. The adsorbent had better adsorption efficiency (∼ 32.8 μg g^-1, after 2 h) for As(V) at neutral pH. Adsorption process mainly followed pseudo-second-order kinetics and Freundlich isotherm models (R²∼0.90) and was facilitated by coulombic, charge-dipole and surface complexation interactions. The regeneration (upto five cycles with 0.1 M NaOH) and competition studies (with binary and cocktail mixture of co-anions) supported the potential field application of the proposed adsorbent.

As(V) and As(III) sequestration by starch functionalized magnetite nanoparticles: influence of the synthesis route onto the trapping efficiency

We report the effect of the synthesis route of starch-functionalized magnetite nanoparticles (NPs) on their adsorption properties of As(V) and As(III) from aqueous solutions. NP synthesis was achieved by two different routes implying the alkaline precipitation of either a mixed Fe²⁺/Fe³⁺ salt solution (MC samples) or a Fe²⁺ salt solution in oxidative conditions (MOP samples). Syntheses were carried out with starch to Fe mass ratio (R) ranging from 0 to 10. The crystallites of starch-free MC NPs (14 nm) are smaller than the corresponding MOP (67 nm), which leads to higher As(V) sorption capacity of 0.3 mmol g_Fe ^-1 to compare with respect to 0.1 mmol g_Fe ^-1 for MOP at pH = 6. MC and MOP starch-functionalized NPs exhibit higher sorption capacities than a pristine one and the difference in sorption capacities between MOP and MC samples decreases with increasing R values. Functionalization tends to reduce the size of the magnetite crystallites and to prevent their agglomeration. Size reduction is more pronounced for MOP samples (67 nm (R0) to 12 nm (R10)) than for MC samples (14 nm (R0) to 9 nm (R10)). Therefore, due to close crystallite size, both MC and MOP samples, when prepared at R = 10, display similar As(V) (respectively, As(III)) sorption capacities close to 1.3 mmol g_Fe ^-1 (respectively, 1.0 mmol g_Fe ^-1). Additionally, according to the effect of pH on arsenic trapping, the electrostatic interactions appear as a major factor controlling As(V) adsorption while surface complexation may control As(III) adsorption.

Spinel-type ferrite nanoparticles for removal of arsenic(V) from water

Spinel ferrite particles (Fe₃O₄, MnFe₂O₄, and CoFe₂O₄) were investigated as magnetic nanosorbents for removing arsenic from spiked water samples. The nanosorbents were collected via magnetic separation from aqueous solutions spiked with an arsenic concentration that mimics the amount of this contaminant in real water samples. This research shows that using amounts of CoFe₂O₄ or MnFe₂O₄ as low as 40 mg/L, the arsenic content in the contaminated water decreased for levels below the maximum admitted value by the World Health Organization for drinking waters (10 μg/L). Moreover, these magnetic nanosorbents also showed good performance for As(V) sorption, when applied to aqueous matrices with variable ionic strength and in the mixtures of other several hazardous contaminants. The good performance observed for the MnFe₂O₄ and CoFe₂O₄ ferrites contrasts with the one observed for Fe₃O₄ nanosorbent, whose efficiency is lower in the removal of As(V) from water, nevertheless increased with the presence of other elements in solution.

Removal of tetracycline from an aqueous solution using manganese dioxide modified biochar derived from Chinese herbal medicine residues

Biochar (BC) derived from Chinese herbal medicine residues has been investigated for its performance as a potential adsorbent in tetracycline (TC) removal. In the present study, a chemical co-precipitation method was carried out to prepare manganese dioxide modified biochar (Mn-BC) to increase its sorption capacity. The properties of the modified biochar were characterized for further enhancing TC removal from an aqueous solution. Mn-BC was successfully synthesized and resulted in a much higher specific surface area, total pore volume and pore diameter. The sorption kinetics of TC on Mn-BC was described by the pseudo-second-order model. The sorption data of Mn-BC were fitted by Langmuir and Freundlich models. The study findings revealed a maximum adsorption capacity of Mn-BC (1:10) to TC was up to 131.49 mg/g. The adsorption process was endothermic and spontaneous. The degradation of TC was further enhanced by MnO₂ acting as an oxidizer on Mn-BC. Overall, the modified biochar derived from Chinese herbal medicine residues is a superior alternative for the removal of TC from an aqueous solution.

Simultaneous oxidation and removal of Sb(III) from water by using synthesized CTAB/MnFe2O4/MnO2 composite

Low levels of antimony (Sb) can be effectively removed from water by adsorption onto various materials, and searching for low-cost and high-efficiency new adsorbents has been a hot topic in recent years. In the present study, the performance of cetyltrimethylammonium bromide (CTAB) modified MnFe₂O₄/MnO₂ composites (CTAB/MnFe₂O₄/MnO₂) as an adsorbent for Sb(III) removal from aqueous solution was investigated. Kinetic study revealed that adsorption of Sb(III) by CTAB/MnFe₂O₄/MnO₂ was fast in the first 430 min and the equilibrium was achieved within 1440 min. The adsorption kinetic data were well fitted with pseudo-second-order model. The maximum adsorption capacity of the synthesized adsorbent for Sb(III) at pH 7 calculated from Langmuir adsorption isotherms in batch experiments was 321.03 mg g^-1. During the adsorption process, Sb(III) can be simultaneously oxidized to Sb(V) and the average oxidation percentage reached 95.43% within 1440 min. The adsorption capacity did not significantly vary with pH. Common metal cations (Ca²⁺ and Mg²⁺) slightly enhanced Sb(III) adsorption at pH 7. In comparison, the effect of anions (Cl^-, NO₃^-, and PO₄^3-) on Sb(III) adsorption was not obvious. The results suggest that CTAB/MnFe₂O₄/MnO₂ is a potential cost-effective adsorbent for Sb(III) removal in water treatment.

Spinel ferrite nanoparticles and nanocomposites for biomedical applications and their toxicity

This review focuses on the biomedical applications and toxicity of spinel ferrite nanoparticles (SFNPs) with more emphasis on the recently published work. A critical review is provided on recent advances of SFNPs applications in biomedical areas. The novelty of SFNPs in addressing the bottleneck problems encountered in the areas of health; in particular, for diagnosis and treatment of tumour cells are well reviewed. Furthermore, research gaps, toxicity of SFNPs and areas which still need more attention are highlighted. Based on the result of this review, the SFNPs have unlimited capacity in cancer treatment, disease diagnosis, magnetic resonance imaging, drug delivery and release. Overall, stepping out of the conventional way of treatment is difficult but also essential in bringing long lasting solution for cancer and other diseases treatment. In fact, the toxicity study and commercialisation of the SFNPs based cancer treatment options are the main challenges and need further study, in order to reduce unforeseen consequences.

Adsorption combined with superconducting high gradient magnetic separation technique used for removal of arsenic and antimony

Manganese iron oxide (MnFe₂O₄), an excellent arsenic(As)/antimony(Sb) removal adsorbent, is greatly restricted for the solid-liquid separation. Through the application of superconducting high gradient magnetic separation (HGMS) technique, we herein constructed a facility for the in situ solid-liquid separation of micro-sized MnFe₂O₄ adsorbent in As/Sb removal process. To the relative low initial concentration 50.0μgL^-1, MnFe₂O₄ material sorbent can still decrease As or Sb below US EPA's drinking water standard limit. The separation of MnFe₂O₄ was mainly relied on the flow rate and the amount of steel wools in the HGMS system. At a flow rate 1Lmin^-1 and 5% steel wools filling rate, the removal efficacies of As and Sb in natural water with the system were achieved to be 94.6% and 76.8%, respectively. At the meantime, nearly 100% micro-sized MnFe₂O₄ solid in the continuous field was readily to be separated via HGMS system. In a combination with the experiment results and finite element simulation, the separation was seemed to be independent on the magnetic field intensity, and the maximum separation capacities in various conditions were well predicted using the Thomas model (R²=0.87-0.99).

Effect of a pH-controlled co-precipitation process on rhodamine B adsorption of MnFe2O4 nanoparticles

We investigated the effect of a pH-controlled co-precipitation process on the adsorption behavior of manganese ferrite (MnFe₂O₄) nanoparticles as well as their structural and magnetic properties. The pH of prepared MnFe₂O₄ nanoparticles is typically an important factor affecting the adsorption capacity of an adsorbent. In this study, MnFe₂O₄ nanoparticles were prepared using a co-precipitation method at four different pH values of 9.0, 9.5, 10.0, and 10.5. The adsorption behaviors on rhodamine B (RhB) by MnFe₂O₄ nanoparticles prepared at different pH values were investigated. It was found that, via a pH-controlled process, MnFe₂O₄ nanoparticles prepared at pH 10.5 showed the highest RhB removal efficiency. The results indicated that the large pore size and surface charge of MnFe₂O₄ nanoparticles improved the adsorption capacities for RhB. Kinetic data were fitted to a pseudo-second order kinetic model and revealed that equilibrium was reached within 60 min. The isotherm data showed that the Langmuir maximum adsorption capacity of the MnFe₂O₄ nanoparticles prepared at pH 10.5 for RhB was 9.30 mg g⁻¹.

The MnFe₂O₄-pH 10.5 sample exhibited high adsorption capacity towards rhodamine B (RhB) solution. The high adsorption capacity towards RhB can be attributed to the large pore size and negative surface charge of MnFe₂O₄ nanoparticles.

Sorption of Cr(III) and Cr(VI) to K2Mn4O9 nanomaterial a Study of the effect of pH, time, temperature and interferences

A Rancieite type material (K₂Mn₄O₉) nanomaterial was synthesized and tested for the removal of chromium (III) and chromium (VI) from aqueous solutions. The synthesized nanomaterial was characterized using powder XRD and SEM. XRD showed weak diffraction peaks at only at the angles associated with K₂Mn₄O₉. The SEM corroborated that the nanoparticles were present; however, the nanoparticles were clustered into larger aggregates. Batch studies were performed to determine the optimum pH, capacity, time dependency, interferences, and the thermodynamics of the binding. The optimum pH for the binding of Cr(III) and Cr(VI) were determined to be pH 5 and pH 2, respectively. Isotherm studies were performed at temperatures of 4 , 25 , and 45 for Cr(III) and Cr(VI) and showed binding capacities of 21.7 mg/g, 36.5 mg/g, 41.8 mg/g for Cr(III). The Cr(VI) binding capacities were 4.22 mg/g, 4.08 mg/g, and 3.25 mg/g at the respective temperatures. The thermodynamic studies showed that the binding processes for the reactions were spontaneous and endothermic, with a ΔH was 17.54 kJ/mol for Cr(III) and 6.05 kJ/mol for Cr(VI). The of sorption for Cr(III) were determined to be -3.88 kJ/mol, -5.83 kJ/mol and -7.03 kJ/mol at the aforementioned temperatures. The ΔG values for the Cr(VI) sorption were determined to be -4.89 kJ/mol, -5.64 kJ/mol, and -6.05 kJ/mol. In addition, the ΔS values for Cr(III) and Cr(VI) were determined to be 77.92 J/mol and 39.49 J/mol, respectively. The thermodynamics indicate that the binding of Cr(III) and Cr(VI) is spontaneous and endothermic.

Adsorption Properties of Nano-MnO₂-Biochar Composites for Copper in Aqueous Solution

There is a continuing need to develop effective materials for the environmental remediation of copper-contaminated sites. Nano-MnO₂–biochar composites (NMBCs) were successfully synthesized through the reduction of potassium permanganate by ethanol in a biochar suspension. The physicochemical properties and morphology of NMBCs were examined, and the Cu(II) adsorption properties of this material were determined using various adsorption isotherms and kinetic models. The adsorption capacity of NMBCs for Cu(II), which was enhanced by increasing the pH from 3 to 6, was much larger than that of biochar or nano-MnO₂. The maximum adsorption capacity of NMBCs for Cu(II) was 142.02 mg/g, which was considerably greater than the maximum adsorption capacities of biochar (26.88 mg/g) and nano-MnO₂ (93.91 mg/g). The sorption process for Cu(II) on NMBCs fitted very well to a pseudo-second-order model (R² > 0.99). Moreover, this process was endothermic, spontaneous, and hardly influenced by ionic strength. The mechanism of Cu(II) adsorption on NMBCs mainly involves the formation of complexes between Cu(II) and O-containing groups (e.g., COO–Cu and Mn–O–Cu). Thus, NMBCs may serve as effective adsorbents for various environmental applications, such as wastewater treatment or the remediation of copper-contaminated soils.

Sequestering of As(III) and As(V) from wastewater using a novel neem leaves/MnFe2O4 composite biosorbent

An arsenic biosorbent comprising neem leaves (NL) and MnFe2O4 particles was developed and its removal potential was investigated. Physicochemical analysis of the NL/MnFe2O4 composite (MNL) was performed for the Brunauer, Emmett and Teller surface area, Fourier transform infrared spectra (FT-IR), and scanning electron microscopy-Energy-dispersive X-ray (EDX). The following parameters were optimized: pH, biosorbent dose, contact time, temperature, and initial arsenic concentration. The optimum pH values achieved for biosorption of As(III) and As(V) were 7.0 and 4.0, respectively, when the equilibrium time was 110 minutes for both. MNL was found to be efficient with 85.217% and 88.154% biosorption efficiency at a concentration of 50 mg/L of As(III) or As(V) solution, respectively. This was also proved by the FT-IR study of arsenic-loaded biosorbent. For establishing the best suitable correlation for the equilibrium curves exploiting the procedure of the nonlinear regression for curve fitting analysis, isotherm studies were conducted for As(III) and As(V) using 30 isotherm models. The pattern of biosorption fitted well with Brouers-Sotolongo isotherm model for As(III) and Langmuir-Freundlich as well as Sips isotherm models for As(V). Dubinin-Radushkevich (D-R) isotherm studies specified that ion exchange might play a significant role. The influence of various co-existing ions at different concentrations was examined. Desorption study was performed using various concentrations of NaOH solution.

Corynebacterium glutamicum MTCC 2745 immobilized on granular activated carbon/MnFe2O4 composite: A novel biosorbent for removal of As(III) and As(V) ions

The optimization of biosorption/bioaccumulation process of both As(III) and As(V) has been investigated by using the biosorbent; biofilm of Corynebacterium glutamicum MTCC 2745 supported on granular activated carbon/MnFe2O4 composite (MGAC). The presence of functional groups on the cell wall surface of the biomass that may interact with the metal ions was proved by FT-IR. To determine the most appropriate correlation for the equilibrium curves employing the procedure of the non-linear regression for curve fitting analysis, isotherm studies were performed for As(III) and As(V) using 30 isotherm models. The pattern of biosorption/bioaccumulation fitted well with Vieth-Sladek isotherm model for As(III) and Brouers-Sotolongo and Fritz-Schlunder-V isotherm models for As(V). The maximum biosorption/bioaccumulation capacity estimated using Langmuir model were 2584.668mg/g for As(III) and 2651.675mg/g for As(V) at 30°C temperature and 220min contact time. The results showed that As(III) and As(V) removal was strongly pH-dependent with an optimum pH value of 7.0. D-R isotherm studies specified that ion exchange might play a prominent role.

Removal of Arsenic from water using synthetic Fe7S8 nanoparticles

In the present study, pyrrhotite was used to remove arsenite and arsenate from aqueous solutions. The Fe₇S₈ was synthesized using a solvothermal synthetic method and it was characterized using XRD and SEM micrographs. Furthermore, the particle size for the nanomaterial Fe₇S₈ was determined to be 29.86 ± 0.87 nm using Scherer's equation. During the pH profile studies, the optimum pH for the binding of As (III) and As (V) was determined to be pH 4. Batch isotherm studies were performed to determine the binding capacity of As(III) and As(V), which was determined to be 14.3 mg/g and 31.3 mg/g respectively for 25°C. The thermodynamic studies indicated that the ΔG for the sorption of As(III) and As(V) ranged from -115.5 to -0.96 kJ/mol, indicating a spontaneous process was occurring. The enthalpy indicated that an exothermic reaction was occurring during the adsorption in which the ΔH was -53.69 kJ/mol and -32.51 kJ/mol for As(III) and As(V) respectively. In addition, ΔS values for the reaction had negative values of -160.46 J/K and -99.77 J/K for the adsorption of As(III) and As(V) respectively which indicated that the reaction was spontaneous at low temperatures. Furthermore, the sorption for As(III) and As(V) was determined to follow the second order kinetics adsorption model.

Removal of Cu (II) and Pb (II) from Aqueous Solution using engineered Iron Oxide Nanoparticles

Nano-sized Fe₃O₄ and Fe₂O₃ were synthesized using a precipitation method. The nanomaterials were tested as adsorbents for the removal of both Cu²⁺ and Pb²⁺ ions. The nanomaterials were characterized using X-ray powder diffraction to determine both the phase and the average grain size of the synthesized nanomaterials. Batch pH studies were performed to determine the optimum binding pH for both the Cu²⁺ and Pb²⁺ to the synthesized nanomaterials. The optimum binding was observed to occur at pH 4 and above. Time dependency studies for Cu²⁺ and Pb²⁺ showed the binding occurred within the first five minutes of contact and remained constant up to 2 hours of contact. Isotherm studies were utilized to determine the binding capacity of each of the nanomaterials for Cu²⁺ and Pb²⁺. The binding capacity of Fe₃O₄ with Cu²⁺ and Pb²⁺ were 37.04 mg/g and 166.67 mg/g, respectively. The binding capacities of the Fe₂O₃ nanomaterials with Cu²⁺ and Pb²⁺ were determined to be 19.61 mg/g and 47.62 mg/g, respectively. In addition, interference studies showed no significant reduction in the binding of either Cu²⁺ or Pb²⁺ to the Fe₃O₄ or Fe₂O₃ nanomaterials in the presence of solutions containing the individual ions Na⁺, K⁺, Mg²⁺ and Ca²⁺ or a solution consisting of a combination of all the aforementioned cations in one solution.

Application of granular activated carbon/MnFe₂O₄ composite immobilized on C. glutamicum MTCC 2745 to remove As(III) and As(V): Kinetic, mechanistic and thermodynamic studies

The main objective of the present study was to investigate the efficiency of Corynebacterium glutamicum MTCC 2745 immobilized on granular activated carbon/MnFe2O4 (GAC/MnFe2O4) composite to treat high concentration of arsenic bearing wastewater. Non-linear regression analysis was done for determining the best-fit kinetic model on the basis of three correlation coefficients and three error functions and also for predicting the parameters involved in kinetic models. The results showed that Fractal-like mixed 1,2 order model for As(III) and Brouser-Weron-Sototlongo as well as Fractal-like pseudo second order models for As(V) were proficient to provide realistic description of biosorption/bioaccumulation kinetic. Applicability of mechanistic models in the current study exhibited that the rate governing step in biosorption/bioaccumulation of both As(III) and As(V) was film diffusion rather than intraparticle diffusion. The evaluated thermodynamic parameters ΔG(0), ΔH(0) and ΔS(0) revealed that biosorption/bioaccumulation of both As(III) and As(V) was feasible, spontaneous and exothermic under studied conditions.

Removal of arsenic from water using nano adsorbents and challenges: A review

Many researchers have used nanoparticles as adsorbents to remove water pollutants including arsenic after modifying the properties of nanoparticles by improving reactivity, biocompatibility, stability, charge density, multi-functionalities, and dispersibility. For arsenic removal, nano adsorbents emerged as the potential alternatives to existing conventional technologies. The present study critically reviewed the past and current available information on the potential of nano adsorbents for arsenic removal from contaminated water and the challenges involved in that. The study discussed the separation and regeneration techniques of nano adsorbents and the performance thereof. The study evaluated the adsorption efficiency of the various nanoparticles based on size of nanoparticles, types of nano adsorbents, method of synthesis, separation and regeneration of the nano adsorbents. The study found that more studies are required on suitable holding materials for the nano adsorbents to improve the permeability and to make the technology applicable at the field condition. The study will help the readers to choose suitable nanomaterials and to take up further research required for arsenic removal using nano adsorbents.

Spectrophotometric determination of basic fuchsin from various water samples after vortex assisted solid phase extraction using reduced graphene oxide as an adsorbent

In this study, a fast and simple vortex assisted solid phase extraction method was developed for the separation/preconcentration of basic fuchsin in various water samples. The determination of basic fuchsin was carried out at a wavelength of 554 nm by spectrophotometry. Reduced graphene oxide which was used as a solid phase extractor was synthesized and characterized by X-ray diffraction, scanning electron microscopy and the Brunauer, Emmett and Teller. The optimum conditions are as follows: pH 2, contact times for adsorption and elution of 30 s and 90 s, respectively, 10 mg adsorbent, and eluent (ethanol) volume of 1 mL. The effects of some interfering ions and dyes were investigated. The method was linear in the concentration range of 50-250 μg L(-1). The adsorption capacity was 34.1 mg g(-1). The preconcentration factor, limit of detection and precision (RSD, %) of the method were found to be 400, 0.07 μg L(-1) and 1.2%, respectively. The described method was validated by analyzing basic fuchsin spiked certified reference material (SPS-WW1 Batch 114-Wastewater) and spiked real water samples.

Study of As(III) and As(V) Oxoanion Adsorption onto Single and Mixed Ferrite and Hausmannite Nanomaterials

The removal of arsenic(III) and arsenic(V) from an aqueous solution through adsorption on to Fe₃O₄, MnFe₂O₄, 50% Mn substituted Fe₃O₄, 75% Mn substituted Fe₃O₄, and Mn₃O₄ nanomaterials was investigated. Characterization of the nanomaterials using XRD showed only pure phases for Mn₃O₄, MnFe₂O₄, and Fe₃O₄. The 50% and 75% substituted nanomaterials were found to be mixtures of Mn₃O₄ and Fe₃O₄. From batch studies the optimum binding pH of arsenic(III) and arsenic(V) to the nanomaterials was determined to be pH 3. The binding capacity for As(III) and As(VI) to the various nanomaterials was determined using Isotherm studies. The binding capacity of Fe₃O₄ was determined to be 17.1 mg/g for arsenic(III) and 7.0 mg/g for arsenic(V). The substitution of 25% Mn into the Fe₃O₄ lattice showed a slight increase in the binding capacity for As(III) and As(VI) to 23.8 mg/g and 7.9 mg/g, respectively. The 50% substituted showed the maximum binding capacity of 41.5 mg/g and 13.9 mg/g for arsenic(III) and arsenic(V). The 75% Mn substituted Fe₃O₄ capacities were 16.7 mg/g for arsenic(III) and 8.2 mg/g for arsenic(V). The binding capacity of the Mn₃O₄ was determined to be 13.5 mg/g for arsenic(III) and 7.5 mg/g for arsenic(V). In addition, interference studies on the effects of SO^2-₄, PO^3-₄, Cl^-, and NO^-₃ investigated. All the interferences had very minimal effects on the As(III) and As(V) binding never fell below 20% even in the presence of 1000 ppm interfering ions.

Thermodynamics, Kinetics, and Activation energy Studies of the sorption of chromium(III) and chromium(VI) to a Mn3O4 nanomaterial

In this study, a manganese oxide, Mn₃O₄ was used to remove chromium(III) and chromium(VI) from aqueous solutions. The Mn₃O₄ nanomaterial was synthesized through a precipitation method, and was characterized using XRD, which confirmed the material had a crystal structure similar to hausmannite. In addition, using Scherrer's equation it was determined that the nanomaterial had an average grain size of 19.5 ± 1.10 nm. A study of the effects of pH on the binding of chromium(III) and chromium(VI) showed that the optimum binding pH was 4 and 3 respectively. Batch isotherm studies were performed to determine the binding capacity of chromium(III), which was determined to be 18.7 mg/g, 41.7 mg/g, and 54.4 mg/g respectively for 4°C, 21°C, and 45°C. Chromium(VI) on the other hand had lower binding capacities of 2.5 mg/g, 4.3 mg/g, and 5.8 mg/g for 4°C, 21°C, 45°C, respectively. Thermodynamic studies performed indicated the sorption process was for the most part controlled by physisorption. The ΔG for the sorption of chromium(III) and Chromium(VI) ranged from -0.9 to -13 kJ/mol, indicating a spontaneous reaction was occurring. The enthalpy indicated a endothermic reaction was occurring during the binding and show ΔH values of 70.6 and 19.1 kJ.mol for chromium(III) and Chromium(VI), respectively. In addition, ΔS for the reaction had positive values of 267 and 73 J/mol for chromium(III) and chromium(VI) which indicate a spontaneous reaction. In addition, the sorption process was found to follow pseudo second order kinetic and the activation energy studies indicated the binding process occurred through chemisorption.

Sorption of Cr(III) and Cr(VI) to High and Low Pressure Synthetic Nano-Magnetite (Fe3O4)Particles

The binding of Cr(III) and Cr(VI) to synthetic nano-magnetie particles synthesized under open vessel conditions and a microwave assisted hydrothermal synthesis techniques was investigated. Batch studies showed that the binding of both the Cr(III) and Cr(VI) bound to the nano-materials in a pH dependent manner. The Cr(III) maximized at binding at pH 4 and 100% binding. Similarly, the Cr(VI) ions showed a maximum binding of 100% at pH 4. The data from the time dependency studies showed for the most part the majority of the binding occurred within the first 5 minutes of contact with the nanomaterial and remained constant thereafter. In addition, the effects of the possible interferences were investigated which showed some effects on the binding of both Cr(III) and Cr(VI). However, the interferences never completely eliminated the chromium binding. Isotherm studies conducted at room temperature showed the microwave synthesized nanomaterials had a binding capacity of 1208 ± 43.9 mg/g and 555 ± 10.5 mg/g for Cr(VI) and Cr(III), respectively. However, the microwave assisted synthesized nanomaterials had capacities of 1705 ± 14.5 and 555± 10.5 mg/g for Cr(VI) and Cr(III), respectively. XANES studies showed the Cr(VI) was reduced to Cr(III), and the Cr(III) remained as Cr(III). In addition, the XANES studies indicated that the chromium remained coordinated in an octahedral arrangement of oxygen atoms.

XANES evidence of arsenate removal from water with magnetic ferrite

Arsenic (As) in groundwater and surface water is a worldwide problem possessing a serious threat to public health. In this study, a magnetic ferrite, was synthesized and investigated for its As(V) removal efficiency. The adsorption of As(V) by magnetic ferrite exhibited an L-shaped nonlinear isotherm, suggesting limiting binding sites on the adsorbent surface. The As K-edge X-Ray Absorption Near-Edge Structure (XANES) revealed that the adsorbed As(V) on ferrite was not reduced to more toxic As(III) by Fe(2+) in the ferrite structure. The maximum As adsorption capacity of ferrite was 14 mg/g at pH 3 and decreased with increasing pH due to enhanced electrostatic repulsion between As(V) and the adsorbent surface. Desorption of As(V) using six different acid and salt solutions showed that the desorption rate decreased in an order of H3PO4 > Na3PO4 > H2SO4 > Na2SO4 > HCl > HNO3. These results suggest that magnetic ferrite without surface modification is an effective adsorbent for removing As(V) from water, which was confirmed by the effective removal of As(V) from contaminated groundwater using this material. The used material can then be recovered using a magnet because of its paramagnetism; the adsorbed As(V) on the material can be recovered using H3PO4 or Na3PO4 solutions.

Study of the thermodynamics of chromium(III) and chromium(VI) binding to iron(II/III)oxide or magnetite or ferrite and magnanese(II) iron (III) oxide or jacobsite or manganese ferrite nanoparticles

Removal of chromium(III) or (VI) from aqueous solution was achieved using Fe3O4, and MnFe2O4 nanomaterials. The nanomaterials were synthesized using a precipitation method and characterized using XRD. The size of the nanomaterials was determined to be 22.4±0.9 nm (Fe3O4) and 15.5±0.5 nm (MnFe2O4). The optimal binding pH for chromium(III) and chromium(VI) were pH 6 and pH 3. Isotherm studies were performed, under light and dark conditions, to determine the capacity of the nanomaterials. The capacities for the light studies with MnFe2O4 and Fe3O4 were determined to be 7.189 and 10.63 mg/g, respectively, for chromium(III). The capacities for the light studies with MnFe2O4 and Fe3O4 were 3.21 and 3.46 mg/g, respectively, for chromium(VI). Under dark reaction conditions the binding of chromium(III) to the MnFe2O4 and Fe3O4 nanomaterials were 5.74 and 15.9 mg/g, respectively. The binding capacity for the binding of chromium(VI) to MnFe2O4 and Fe3O4 under dark reaction conditions were 3.87 and 8.54 mg/g, respectively. The thermodynamics for the reactions showed negative ΔG values, and positive ΔH values. The ΔS values were positive for the binding of chromium(III) and for chromium(VI) binding under dark reaction conditions. The ΔS values for chromium(VI) binding under the light reaction conditions were determined to be negative.