Chitosan based titanium and iron oxide hybrid bio-polymeric nanocomposites as potential corrosion inhibitor for mild steel in acidic medium.

Biopolymer chitosan (CS), chitosan grafted acrylamide based titanium dioxide (CS-g-PAM/TiO2) and magnetite (CS-g-PAM/Fe3O4) hybrid nanocomposites have been synthesized through free radical graft co-polymerization and successfully validated as corrosion inhibitors for mild steel in 15 % HCl solution. The synthesized compounds have been characterized through FTIR, APC, XRD and TEM. The thermal stability of the nanocomposites was established by TGA. The anticorrosive performance was determined through gravimetric measurements and by electrochemical study. According to EIS technique it was observed that CS-g-PAM/TiO2 and CS-g-PAM/Fe3O4 showed maximum 97.19 % and 95.49 % efficiency respectively. Langmuir adsorption isotherm is obeyed in each case. The activation and adsorption parameters have been determined from isotherm study. FESEM and AFM confirmed better adsorption layer formed by composites over mild steel surface. The elemental composition of the metal samples was proved by the XPS investigation. DFT and ANOVA test further corroborates the experimental results.

Comparative characterization of cyanide-containing steel industrial wastewater.

In the steel industry, cyanide in the wastewater is a major environmental concern. There are several chemical, physical, and biological treatment processes available for the removal of cyanide from industrial wastewater. But the efficacy of every treatment process depends on the complex elemental matrix of wastewater and the interference associated with them. Thus, water characterization plays a vital part in finding a suitable cyanide treatment process for any wastewater. Characterization data can give a clear overview of the complexity of cyanide in the wastewater, which ultimately helps in selecting the right remediation process. The present work includes comparative characterization of coke plant and blast furnace wastewater collected from an integrated steel plant. Three months of data for physico-chemical properties of the two different sources were analysed and compared. Pearson's correlation analysis of physico-chemical properties with free cyanide was also studied. The different forms of cyanide in coke plant and blast furnace water were also characterised, along with interference associated with them. It was observed that the water matrix of coke plant and blast furnace effluents are totally different. It was also evident that free cyanide concentration is much more affected in coke plant wastewater than in blast furnace water.

Medical Geological assessment of fluoride contaminated groundwater in parts of Indo-Gangetic Alluvial plains.

As drinking water is considered as a major pathway of exposure to fluoride in the human body, an endeavor has been made for the assessment of the non-carcinogenic health risk by using hazard quotient (HQ) of fluoride for males, females, and children separately in fluoride affected ground water areas of Indo-Gangetic Alluvial Plains. The study suggests that children groups are more prone to the non-carcinogenic risk of fluoride in the area as HQ for fluoride is more than unitary in 44% (Pre-monsoon) and 38% (Post-monsoon) samples respectively. Field survey conducted in fluoride-affected villagers of the study area portrays cases of mottling of teeth and bone deformities depending on the duration and dosage of fluoride consumption. Petrographic observations of host rocks coupled with molar ratios of chemical species studies exemplify that weathered material developed over the granite-gneiss, mica-schist, amphibolite, granitic intrusive and pegmatite veins due to weathering and extensive water-rock interaction resulting higher concentration of fluoride in groundwater. Likewise, the base exchange index (r1) and meteoric genesis index (r2) advocates that most of the samples belong to Na+-HCO3- type and meteoric origin respectively, and substantiate longer residence time of water along with solute acquisition processes are responsible for elevated fluoride in groundwater. It is, therefore, solar energy-driven electrolytic de-fluoridation technology ought to be provided on a priority basis to the affected inhabitants besides the implementation of rainwater harvesting schemes for mitigation/ dilution of elevated fluoride concentration.

Geochemical signatures and isotopic systematics constraining dynamics of fluoride contamination in groundwater across Jamui district, Indo-Gangetic alluvial plains, India.

A data set of 76 water samples are obtained from surface and sub-surface water bodies to investigate chemical parameters and stable isotopic signatures in order to drive factors leading to fluoride (F-) contamination in groundwater of parts of Jamui district, India. Hydrochemical facies reveals that F- concentration is lower in Ca2+-HCO3- facies representative of recharge area, while discharge area has a tendency towards Na+-HCO3- facies with elevated F- concentration. The ionic ratios Na+/Ca2+>1, Na+/Cl->1, (Ca2++Mg2+)/HCO3-<1, Na++K+ = 0.5TZ+ and Ca2++Mg2+ = TZ+ witness silicate weathering by water-rock interaction coupled with ion exchange and prolonged residence time, are the principle factors for fluoride contamination (3.6 mg/L to 5.8 mg/L) in 67% of deeper bore wells. Geochemical modelling testifies excess of alkalinity due to the dominance of bicarbonate ion leading to calcite precipitation and dissolution of fluoride in solution contributing to fluoride contamination. The chemometric analysis reveals that the water chemistry of the study area is controlled by both anthropogenic and natural sources, and enrichment of fluoride in groundwater is possibly from geogenic source (fractured granite gneiss). The stable isotope plot shows that most of the samples fall along local meteoric water line indicating that the groundwater is originated from local precipitation with a possibility of evaporative enrichment. Groundwater enriched in δ18O is positively correlated with F- suggesting evaporation and longer residence time of water. Spatially elevated F- prevails in the eastern bank of Kiul River and along the groundwater flow direction, which is attributed to control of dynamics of hydrogeological conditions.

Correction: Solution-processed Cu2XSnS4 (X = Fe, Co, Ni) photo-electrochemical and thin film solar cells on vertically grown ZnO nanorod arrays.

[This corrects the article DOI: 10.1039/C6RA24149B.].

Flocculation properties of polyacrylamide grafted carboxymethyl guar gum (CMG-g-PAM) synthesised by conventional and microwave assisted method.

A novel polymeric flocculant based on polyacrylamide grafted carboxymethyl guar gum (CMG-g-PAM) has been synthesised by grafting polyacrylamide chains onto CMG backbone using conventional redox grafting and microwave assisted grafting methods. Under optimum grafting conditions, 82% and 96% grafting efficiencies have been observed in case of conventional and microwave assisted methods respectively. The optimum sample has been characterized using viscometry, spectroscopic analysis, elemental analysis, molecular weight and radius of gyration determination. The flocculation characteristics of grafted and ungrafted polysaccharides have been evaluated in kaolin suspension, municipal sewage wastewater and decolourization efficiency of a dye solution (methylene blue). It is evident from results that CMG-g-PAM synthesised by microwave assisted grafting method is showing best flocculation characteristics.