Uday Chand Ghosh

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.

Studies on Management of Chromium(VI) – Contaminated Industrial Waste Effluent using Hydrous Titanium Oxide (HTO)

The anion exchange behaviour of hydrous titanium oxide(HTO) has been exploited for the management of industrialwaste effluents contaminated with chromium(VI). Theadsorption of chromium(VI) by HTO (74.0–140.0 micron) in thepH range 0.5–8.0 has been studied. It is found that theadsorption of chromium(VI) by HTO is at a maximum in the pHrange 1.5–2.0. The interference of diverse foreign ionssuch as nitrate, chloride, sulfate, phosphate, calcium,magnesium, nickel, iron(III), barium etc. on the adsorptionof chromium(VI) by HTO at optimum pH has been investigatedby a batch-operation technique. Break-through capacity,adsorption and elution of chromium(VI) using HTO have beenstudied. It is found that HTO could be reused as anadsorbent for chromium(VI). Finally, chromium(VI) wasrecovered as insoluble chromate compound from waste effluentof Hindustan Motor Limited (HML) of Hooghly, West Bengal, India.

Physicochemical Aspects on Fluoride Adsorption for Removal from Water by Synthetic Hydrous Iron(III) – Chromium(III) Mixed Oxide

Fluoride removal with varying different parameters at 303 ± 1.6 K and pH 6.5 ± 0.2 was investigated by hydrous iron(III)-chromium(III) bimetal oxide. The kinetic and equilibrium data fitted with the pseudo-second order and Langmuir isotherm equations very well (R2 = 0.99−1.00), respectively. The Langmuir capacity (θ) and free energy (EDR) of adsorption evaluated were 16.34 (±0.50) mg·g−1 and 15.81 kJ·mol−1, respectively. The estimated thermodynamic parameters viz. ΔH0, ΔG0, and ΔS0 indicated that the reaction was endothermic but spontaneous for entropy increase. The small-scale column filtration of high fluoride (C0 = 7.37 mg·L−1) water gave encouraging results.

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.

Covalent Immobilization of Protein onto a functionalized Hydrogenated Diamond-like Carbon Substrate

Hydrogenated diamond-like carbon (HDLC) has an atomically smooth surface that can be deposited on high-surface area substrata and functionalized with reactive chemical groups, providing an ideal substrate for protein immobilization. A synthetic sequence is described involving deposition and hydrogenation of DLC followed by chemical functionalization. These functional groups are reacted with amines on proteins causing covalent immobilization on contact. Raman measurements confirm the presence of these surface functional groups, and Fourier transform infrared spectroscopy (FTIR) confirms covalent protein immobilization. Atomic force microscopy (AFM) of immobilized proteins is reproducible because proteins do not move as a result of interactions with the AFM probe-tip, thus providing an advantage over mica substrata typically used in AFM studies of protein. HDLC offers many of the same technical advantages as oxidized graphene but also allows for coating large surface areas of biomaterials relevant to the fabrication of medical/biosensor devices.

Characterization of Agglomerated Nanosized Titanium(IV) Oxide Prepared by Two Pathways and Their Performance Toward Cu(II) Adsorption

ABSTRACT Two different TiO2 particles with nanodimensions were prepared by sol-gel (TO-S) and low temperature chemical precipitation method (TO-P) from a TiCl4 precursor. As a result, the TO-S preparation was according to the “green chemistry” method because it did not involve any toxic or hazardous by-products. The average size of the nanoparticles of TO-S and TO-P were 27 and 12 nm, respectively. Agglomerates of these nanodimensional particles should have high surface area and can be useful for adsorptive removal of toxic species from aqueous solutions. Higher Cu(II) adsorption capacity of TO-P than TO-S may be attributed to the hydrated nature of the former material.

Synthesis and characterisation of cerium(IV)-incorporated hydrous iron(III) oxide as an adsorbent for fluoride removal from water

Surface-altered hydrous iron(III) oxide incorporating cerium(IV) (CIHFO) was prepared and characterised via modern analytical tools for applications in fluoride removal from groundwater. The material with a Fe : Ce ratio of 1.0 : 0.5 (mol : mol) calcined at 473 K shows 24.8 ± 0.5 mg F− g−1 adsorption capacity at pH 5.0–7.0 from a solution with a concentration of 15.0 mg L−1; the material was established to be microcrystalline (∼5 nm) with a 140.711 m2 g−1 surface area, irregular surface morphology and porous structure. The time-dependent fluoride adsorption capacities of CIHFO at 293, 303 and 313 K are well described by the pseudo-first order, pseudo-second order and Weber–Morris kinetic models, respectively. The adsorption reaction occurs via a film/boundary layer diffusion process. The very low Arrhenius activation energy (Ea = 0.026 kJ mol−1) indicates the high feasibility of fluoride adsorption over CIHFO. The equilibrium data fit better with the Freundlich and Redlich–Peterson (g < 1.0) isotherms than with the Langmuir isotherm, which suggests multilayer adsorption. The values of the Freundlich parameters, n = 3.10, 4.47 and 7.57 and KF = 8.58, 10.88 and 11.25 at 293, 303 and 313 K, respectively, indicate high affinity for fluoride. Thermodynamic analysis of the reaction equilibrium shows that the reaction is highly exothermic (ΔH0 = −25.924 and −36.279 kJ mol−1 for Ci = 25.0 and 35.0 mg L−1), whereas the negative ΔG0 values indicate the spontaneous nature of the reaction. The fluoride adsorption over CIHFO occurs via ion-exchange that progresses to chemisorption. The presence of sulphate shows an adverse influence on fluoride adsorption by CIHFO, and the fluoride level of 2.4 g per L groundwater (9.05 mg F L−1) can be reduced below the permissible value.

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.