Kaushik Gupta

Arsenic removal using hydrous nanostructure iron(III)-titanium(IV) binary mixed oxide from aqueous solution.

The synthetic bimetal iron(III)-titanium(IV) oxide (NHITO) used was characterized as hydrous and nanostructured mixed oxide, respectively, by the Föurier transform infra red (FTIR), X-ray diffraction (XRD) pattern and the transmission electron microscopic (TEM) image analyses. Removal of As(III) and As(V) using the NHITO was studied at pH 7.0 (+/-0.1) with variation of contact time, solute concentration and temperature. The kinetic sorption data, in general, for As(III) described the pseudo-first order while that for As(V) described the pseudo-second order equation. The Langmuir isotherm described the equilibrium data (303 (+/-1.6)K) of fit was well with the Langmuir model. The Langmuir capacity (q(m), mg g(-1)) value of the material is 85.0 (+/-4.0) and 14.0 (+/-0.5), respectively, for the reduced and oxidized species. The sorption reactions on NHITO were found to be endothermic and spontaneous, and took place with increasing entropy. The energy (kJ mol(-1)) of sorption for As(III) and As(V) estimated, respectively, is 9.09 (+/-0.01) and 13.51 (+/-0.04). The sorption percentage reduction of As(V) was significant while that of As(III) was insignificant in presence of phosphate and sulfate. The fixed bed NHITO column (5.1 cm x 1.0 cm) sorption tests gave 3.0, 0.7 and 4.5L treated water (As content < or = 0.01 mg L(-1)) from separate As(III) and As(V) spiked (0.35+/-0.02 mg L(-1)) natural water samples and from high arsenic (0.11+/-0.01 mg L(-1)) ground water, respectively when inflow rate was (0.06 L h(-1)).

Manganese associated nanoparticles agglomerate of iron(III) oxide: Synthesis, characterization and arsenic(III) sorption behavior with mechanism

Three samples of manganese associated hydrous iron(III) oxide (MNHFO), prepared by incinerating metal hydroxide precipitate at T (± 5)=90, 300 and 600°C, showed increase of crystalline nature in XRD patterns with decreasing As(III) removal percentages. TEM images showed the increase of crystallinity from sample-1 (MNHFO-1) to sample-3 (MNHFO-3). Dimensions (nm) of particles estimated were 5.0, 7.0 and 97.5. Optimization of pH indicated that MNHFO-1 could remove aqueous As(III) efficiently at pH between 3.0 and 7.0. Kinetic and equilibrium data of reactions under the experimental conditions described the pseudo-second order and the Langmuir isotherm equations very well, respectively. The Langmuir capacity (q(m)) estimated was 691.04 mmol kg(-1). The values of enthalpy, Gibbs free energy and entropy changes (ΔH(0)=+23.23 kJ mol(-1), ΔG(0)=-3.43 to -7.20 kJ mol(-1) at T=283-323K, ΔS(0)=+0.094 kJ mol(-1)K(-1)) suggested that the reaction was endothermic, spontaneous and took place with increasing entropy. The As(III) sorbed by MNHFO-1 underwent surface oxidation to As(V), and evidences appeared from the XPS and FTIR investigations. MNHFO-1 packed column (internal diameter: 1.0 cm, height: 3.7 cm) filtered 11.5 dm(3) groundwater (105 μg As dm(-3)) with reducing arsenic concentration to ≤ 10 μg dm(-3).

Arsenic bioaccumulation in rice and edible plants and subsequent transmission through food chain in Bengal basin: a review of the perspectives for environmental health

Arsenic (As) is a metalloid that poses serious environmental threats due to its behemoth toxicity and wide abundance. The use of arsenic-contaminated groundwater for irrigation purpose in crop fields elevates arsenic concentration in surface soil and in the plants. In many arsenic-affected countries, including Bangladesh and India, rice is reported to be one of the major sources of arsenic contamination. Rice is much more efficient at accumulating arsenic into the grains than other staple cereal crops. Rice is generally grown in submerged flooded condition, where arsenic bioavailability is high in soil. As arsenic species are phytotoxic, they can also affect the overall production of rice, and can reduce the economic growth of a country. Once the foodstuffs are contaminated with arsenic, this local problem can gain further significance and may become a global problem, as many food products are exported to other countries. Large-scale use of rainwater in irrigation systems, bioremediation by arsenic-resistant organisms and hyperaccumulating plants, and the aerobic cultivation of rice are some possible ways to reduce the extent of bioaccumulation in rice. Investigation on a complete food chain is urgently needed in the arsenic-contaminated zones, which should be our priority in future researches.

Arsenic(III) sorption on nanostructured cerium incorporated manganese oxide (NCMO): A physical insight into the mechanistic pathway

Arsenic(III) sorption was investigated with nanostructured cerium incorporated manganese oxide (NCMO). The pH between 6.0 and 8.0 was optimized for the arsenic(III) sorption. Kinetics and equilibrium data (pH=7.0±0.2, T=303±1.6 K, and I=0.01 M) of arsenic(III) sorption by NCMO described, respectively, the pseudo-second order and the Freundlich isotherm equations well. The sorption process was somewhat complicated in nature and divided into two different segments, initially very fast sorption followed by slow intraparticle diffusion process. Sorption reaction of arsenic(III) on NCMO was endothermic (ΔH°=+13.46 kJ mol(-1)) and spontaneous (ΔG°=-24.75 to -30.15 kJ mol(-1) at T=283-323 K), which took place with increasing entropy (ΔS°=+0.14 kJ mol(-1)K(-1)) at solid-liquid interface. Energy of arsenic(III) sorption estimated by analyzing the equilibrium data using the D-R isotherm model was 15.4 kJ mol(-1), indicating the ion-exchange type mechanism. Raman, FT-IR, pH effect, desorption, etc. studies indicated that arsenic(III) was oxidized to arsenic(V) during the sorption process.

Tuned synthesis and characterizational insight into β-cyclodextrin amended hydrous iron-zirconium hybrid oxide: a promising scavenger of fluoride in aqueous solution

The consumption of water contaminated with fluoride (>1.5 mg L−1) causes serious problems to public health and ultimately leads to skeletal fluorosis. Thus, the development of more efficient fluoride scavenging materials for designing water filters is an immediate task for researchers. β-Cyclodextrin (β-CD) amended hydrous iron–zirconium hybrid oxide (CHIZO), which is a new type of surface modified highly selective composite in organic–inorganic frameworks, is synthesized and characterized using various state of the art analytical tools, and its efficacy on fluoride removal from an aqueous solution is explored. The agglomerated micro structured composite material has no significant fingerprint such as surface appearance in TEM images and is inclined to possess very poor crystallinity. The BET analysis of CHIZO reveals a surface area of 0.2070 m2 g−1 and pore volume of 0.0476 cm3 g−1. The highly pH dependent fluoride adsorption by CHIZO decreases with an increase in pH, and pseudo-second order kinetics control the reaction. The Langmuir isotherm was recognized to be the best fit model to describe the adsorption equilibrium with a significantly higher monolayer adsorption capacity of fluoride (31.35 mg g−1) than the host hydrous Fe–Zr oxide (8.21 mg g−1) at pH ∼7.0 and 303 K. The thermodynamically spontaneous nature of CHIZO is due to the exothermic nature of the reaction. In addition, phosphate and sulphate show an adverse effect on fluoride adsorption. β-CD forms inclusion complexes by taking up fluoride ions from water into its central cavity and the driving forces associated with the complex formation include the release of enthalpy-rich water molecules from its cavity, electrostatic interactions, hydrogen bonding and release of conformational strain. The poor regeneration of the spent adsorbent even in 1.0 M NaOH (below 20%) is probably a consequence of entrapping fluoride inside the cavity of β-CD with hydrogen bonding. It has been found that only 0.9 g of CHIZO is able to reduce the fluoride level to below 1.0 mg L−1 in one-litre of fluoride spiked (5.0 mg L−1) natural water sample. The present study thus reveals that CHIZO could be an efficient adsorbent for fluoride because of its high adsorption capacity and economical viability.

Synthesis, characterization and trivalent arsenic sorption potential of Ce-Al nanostructured mixed oxide

Arsenic contamination in the ground water has serious health consequences in many parts of the world. The surface sorption method for arsenic mitigation has been widely investigated due to its simple method, inexpensive operation, highly efficient and low content of by-products. In the present study, nanostructured hydrated cerium aluminum oxide (NHCAO) was synthesized and characterized and its arsenic (III) sorption behavior from the aqueous solution was studied. The material was characterized in SEM, FE-SEM, TEM, AFM, XRD, and FT-IR. Batch method was used for the kinetics of As (III) sorption on nanoparticles at 303 (± 1.6) K and at pH 7.0 (± 0.2). The experiments on isotherm subject were performed individually at 288K, 303K, 318K temperatures at pH 7.0 (± 0.2) using the batch sorption method. In the kinetics study of arsenic (III) sorption, the sorption percentage was observed to remain nearly unchanged up to pH 9.0, thereafter only slight reduction in sorption percentage. The equilibrium sorption results were tested using the models of Langmuir and the Freundlich isotherm. The Langmuir model is the most fitted model for the sorption reaction. NHCAO was highly efficient in As(III) removal out of the water in the extensive range of pH and could be used for arsenic removal from contaminated water.