Boron Bioaccumulation by the Dominant Macrophytes Grown in Various Discharge Water Environments

Microwave-assisted desulphurization of coal in alkaline medium and conditions optimization by response surface methodology

The coal is an imperative source of energy, which on combustion, it emits sulphur dioxide, which cause air pollution. In the present study, microwave mediated desulphurization of coal was investigated and input variables were optimized by response surface methodology (RSM). The proximate analysis and ultimate analysis report indicate the sample belongs to subbituminous having sulphur (6.96%), volatile matter (34.5%) and calorific value (5099 kcal/kg). Under microwave irradiation, up to 68% of sulphur was leached in alkaline medium. The particle size of coal, concentration of potassium hydroxide (KOH), microwave exposure time and power of microwave radiation were systematically optimized for maximum desulphurization of the coal. Under optimum conditions of the process variables, 63.06% desulphurization of coal was achieved. The optimum levels of process variables are as, particle size 500 µm, irradiation time 8.54 min, radiation power 720 W and concentration of KOH 15% (w/v). Findings revealed that the microwave-assisted desulphurization under alkaline condition furnished promising efficiency, which can be employed for the desulphurization of coal.

Phytoremediation, bioaccessibility and ecotoxicological risk assessment of arsenic in a gold mining area

The physicochemical and biological parameters of aquatic ecosystems are directly affected by mining activities, increasing the ecotoxicological risk related to exposure to contaminants and pollutants. In this study, a native and adapted floating aquatic macrophyte was used in a gold mining area as a model organism to assess the environmental risk and its potential application in bioremediation of heavy metals. The physicochemical parameters of water and sediments were evaluated, as well as the phytoremediation parameters (bioconcentration and translocation factors) of Hydrocotyle ranunculoides L. The results showed a significant bioconcentration of Cr, Pb, Cu, and Zn in the roots of the macrophyte (high BCF: As > Cu > Zn > Pb > Cr), confirming its suitability for use in rhizofiltration. Regarding arsenic bioconcentration, H. ranunculoides demonstrated a high BCF and TF > 1, indicating its phytoextraction potential, an essential requirement for plants to be used in bioremediation programs.

Cationic distributions and dielectric properties of magnesium ferrites fabricated by sol-gel route and photocatalytic activity evaluation

Sol-gel auto combustion method was adopted to fabricate magnesium ferrite (MgFe2O4) nanoparticles. The structural and morphological properties was studied by XRD, FTIR, and SEM analysis. The average particle sizes of MgFe2O4 was in the range of 35–55 nm. The octahedral & Tetrahedral bond lengths, R AE (tetrahedral edge length), R BE (shared octahedral edge length) and R BEU (individual octahedral edge length), cationic radii (tetra and octa-sites) were also determined. The magnetic strength also showed direct reliance on bond angle and indirect to bond length. Hoping length L a and L b and bond angles are also measured. The frequency dependent conductivity and dielectric properties of MgFe2O4 were investigated by Impedance analyzer. The photocatalytic activity (PCA) is appraised against MB (methylene blue) dye and MgFe2O4 calcined at 800 °C showed promising degradation (78%) under visible light irradiation. The findings revealed that MgFe2O4 is can harvest the solar light, which could be employed for the remediation of wastewater contains textile dyes.

Ionizing radiation based advanced oxidation process for reactive orange 122 dye degradation and kinetics studies

In the current study, the degradation of reactive orange 122 (RO 122) dye was carried out under UV and gamma irradiation in presence of H2O2. The effect of variables such as UV exposure time, gamma-ray absorbed dose, initial concentration of dye and oxidant dose were investigated. The removal of 64.10, 58.84 and 55.46 (%) was observed for 50, 100 and 150 (mg/L) dye concentrations, respectively using UV radiation time of 150 (min). The degradation was enhanced to 80.39, 69.95 and 67.01 (%) when UV radiation was employed in the presence of H2O2 (0.5 mL/L) for above concentrations respectively. The degradation was further improved to 97, 92.54 and 81.32 (%) using 5 kGy absorbed dose along with H2O2 (0.5 mL/L). The reduction in chemical oxygen demand (COD) was 77, 64 and 57 (%) using UV/H2O2 (0.5 mL/L), while 63, 56 and 53 (%) in case of gamma/H2O2 for aforementioned concentrations. The removal efficiency (G-value), dose constants (k), dose indispensable for 50, 90 and 99 (%) degradation (D 0.5, D 0.90, and D 0.99) after the treatment with gamma radiation were determined. The G-value was noted as 0.46–0.0711 for 50–150 mg/L dye concentration for gamma irradiated samples which improved to 0.57–0.1204 for above mentioned concentrations in presence of H2O2. The FTIR analysis showed that all the peaks were disappeared using gamma/H2O2 at 5 kGy absorbed dose except a minor peak of −CO stretching. The degradation mechanism of dye followed pseudo-first-order kinetics. A significant decrease in peak area was observed by the HPLC analysis after treating the dye samples with gamma/H2O2 (0.5 mL/L) at absorbed dose of 5 kGy which has proven the process efficiency for dye degradation.

Size controlled synthesis of silver nanoparticles: a comparison of modified Turkevich and BRUST methods

In the present investigation, silver nanoparticles were synthesized and a comparative analysis was performed of modified Turkevich and BRUST methods. Silver nitrate precursor was reduced by trisodium citrate dihydrate and ascorbic acid was used as a surfactant. Based on Turkevich and BRUST methods, the process variables, i.e., temperature, reducing agent concentration, stirring speed, mode of injecting reducing agent/precursor to large excess volume of either precursor/reducing agent were studied. The size of the particles was preliminarily ascertained by DLS studies and it was found that modified BRUST method yielded silver nanoparticles with average particle size of 25 nm, while modified Turkevich method furnished nanoparticles with average particle size of 15 nm. The silver nanoparticles were characterized by employing the UV/visible, Zeta sizer, scanning electron microscopy (SEM) and energy dispersive microscopy (EDX) techniques. Results revealed that the silver nanoparticles size can be controlled by optimizing the conditions of modified Turkevich and BRUST methods.

SnO2/UV/H2O2 and TiO2/UV/H2O2 Efficiency for the Degradation of Reactive Yellow 160A: By-Product Distribution, Cytotoxicity and Mutagenicity Evaluation

Advanced oxidation processes (AOPs) have emerged as a promising approach for the removal of organic dyes from effluents. Different AOPs were employed for the degradation of Reactive Yellow 160A (RY-160A) dye, i.e., SnO2/UV/H2O2 and TiO2/UV/H2O2. In the case of UV treatment, maximum degradation of 28% was observed, while UV/H2O2 furnished 77.78% degradation, and UV/H2O2/TiO2 degraded the RY-160A dye up to 90.40% (RY-160A 30 mg/L, 0.8 mL of H2O2). The dye degradation was 82.66% in the case of UV/H2O2/SnO2 at pH 3. FTIR and LC-MS analyses were performed in order to monitor the degradation by-products. The cytotoxicity and mutagenicity of RY-160A dye were evaluated by hemolytic and Ames (TA98 and TA100 strains) assays. It was observed that the RY-160A dye solution was toxic before treatment, and toxicity was reduced significantly after treatment. Results indicated that UV/H2O2/TiO2 is more efficient at degrading RY-160A versus other AOPs, which have potential application for the remediation of dyes in textile effluents.

Cellulose, clay and sodium alginate composites for the removal of methylene blue dye: Experimental and DFT studies

Cellulose/clay/sodium alginate composites were prepared and employed for the removal of methylene blue (MB) dye. Cellulose was extracted from a paper mill waste and used for composite preparation with sodium alginate (Na-Alg) and clay. MB dye removal was analyzed at different operating conditions (pH, initial concentration, temperature, composite dose). This dye was adsorbed up to 90% for an equilibrium time of 60 min at optimum level of adsorbent dose (0.05 g), temperature (30 °C) and pH (i.e., 7 and 11 for cellulose-Na-Alg and cellulose-Na-Alg-clay, respectively). Kinetics and isotherms of MB adsorption were quantified and modeled. Results showed that MB dye adsorption data followed the pseudo-first order kinetics and a statistical physics model was used to analyze the adsorption mechanism. Thermodynamic calculation revealed that the MB dye adsorption on these composites was an exothermic, spontaneous and feasible process. The composites were regenerated with HCl thus contributing to their reutilization in subsequent adsorption cycles. The DFT (density functional theory) calculations were executed to explain the interactions responsible for the adsorption of MB dye on the composites. Results revealed that the Na-Alg-cellulose composites were effective for the MB dye removal. Therefore, these composites can be considered as low-cost alternative adsorbents for the pollution remediation caused by dyes in industrial effluents and wastewater.

Kinetics of methylene blue dye adsorptive removal using halloysite nanocomposite hydrogels

In the present work, halloysite nano-clay (HNTs) based hydrogel was fabricated and their efficiency for the removal of methylene blue dye was studied. The hydrogel films were prepared with varying amount of halloysite nano-clay via facile solution casting method. Effect of halloysite clay on adsorption performance of composite was investigated. The hydrophobic thermoplastic synthetic polymer, polylactic acid (PLA) was blended with hydrophilic polymer polyvinyl alcohol (PVA) and HNTs to synthesize hydrogels. Swelling behavior and antimicrobial efficiency was also evaluated. The halloysite incorporating films showed excellent antibacterial activity. Swelling capacity of hydrogel with increased halloysite content was reduced due to increased crosslinking among polymer chains. Halloysite incorporated hydrogel exhibited higher adsorption ability as compared to film comprising of only PVA and PLA and dye removal followed pseudo first order kinetics. Film with 0.03 g HNTs rapidly attained adsorption-desorption equilibria and removed the dye completely within 30 min. Results confirmed that synthesized film could be potentially used for the removal of cationic dye and fabricated hydrogel film have promising potential for wastewater treatment since a higher adsorption capacity was observed for halloysite nano-clay incorporated hydrogel.

The electrochemical, dielectric, and ferroelectric properties of Gd and Fe doped LaNiO3 with an efficient solar-light driven catalytic activity to oxidize malachite green dye

This work investigates the effects of double ion substitution on the ferroelectric, electrochemical, dielectric and photocatalytic properties of Gd and Fe doped La_1-yGd_yNi_1-xFe_xO₃ nanoparticles (NPs). La_1-yGd_yNi_1-xFe_xO₃ was fabricated by facile micro-emulsion path and its properties were studied by thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman scattering, Fourier Transform of Infrared (FTIR), energy dispersive x-rays (EDX) techniques. It has a distorted rhombohedral shape with crystallite size within the range of 17-23 nm. The doped material has a spherical heterogeneous morphology, and its surface area increased with increased doping. The electrochemical (CV, EIS, and I-V), conductivity and dielectric (dielectric constant and low dielectric & tangent loss) properties of La_1-yGd_yNi_1-xFe_xO₃ were dependent on the contents of the dopants (Gd and Fe). The doped material had improved specific capacitance compared to the undoped LaNiO₃ due to the synergistic effect of Gd and Fe on the doped materials. The conductivity of Gd and Fe doped LaNiO₃ 5.16 × 10⁴ Sm^-1 was enhanced compared to the undoped LaNiO₃ 3.52 × 10^-2 Sm¹. Furthermore, hysteresis loop was used to investigate the coercivity (Hc), saturation magnetization (Ms) and remanence (Mr) of the material. The Ms and Mr values were enhanced with the content of the dopants. The photocatalytic activity (PCA) of the material in degrading malachite green (MG) dye was studied. La_1-yGd_yNi_1-xFe_xO₃ NPs was able to degrade up to 96.4% of the dye under visible light irradiation in 50 min. La_1-yGd_yNi_1-xFe_xO₃ has remarkable dielectric, electrochemical, ferroelectric and photo-catalytic properties and have potential applications in microwave, electrical, electronic, energy storage devices. It is also an active photo-catalyst material for the removal/oxidation of toxic pollutants from the environment.