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Nitrate and fluoride are among the key chemicals that cause large scale health effects through drinking water exposure. In this study, the nitrate and fluoride content from drinking water sources of the Chennai River basin districts of Chennai, Kancheepuram and Tiruvallur in Tamil Nadu, India were analyzed to map their spatial distribution. Out of the 103 groundwater samples analyzed, 84 (81.6%) and 79 (76.7%) samples were found to possess below permissible limits of nitrate (45.0 mg/L) and fluoride (1.0 mg/L), respectively. Chennai city, with high population density was not found to be a nitrate and fluoride endemic region. The maximum nitrate concentrations of 143.9 and 132.0 mg/L were found to occur in water sourced from two relatively isolated hotspots, a borewell in Sottupakkam and an openwell in Sirunallur, respectively of Kancheepuram district. Tiruvallur (maximum 2.7 mg/L at Tiruvallur town) and Kancheepuram (maximum 2.6 mg/L at Chengalpattu town) districts had more than 10 fluoride hotspots each with content higher than the permissible limit, which is most probably due to fluoride leaching from mineral-rich rocks in these regions. The fluoride concentration levels appeared to correlate better against water quality parameters (total dissolved solids, electrical conductivity, alkalinity, total hardness, chloride and sulphate) studied when compared with the nitrate concentration levels. The fluoride concentrations also appeared to have a relatively higher correlation with alkalinity and hardness which can be attributed to concomitant release of bicarbonate, calcium and magnesium ions during the fluoride leaching process from mineral-rich rocks in these regions. Furthermore, the non-carcinogenic health risk associated with nitrate and fluoride in water ingestion in infants, children and adults was evaluated with the United States Environmental Protection Agency (U.S. EPA) method. The percentage exceedance of total hazard index limit for infants, children and adults in Chennai district was 95.8%, 58.3% and 8.3%, respectively, while it was 100.0%, 100.0% and 61.0%, respectively in Kancheepuram district and 97.4%, 97.4% and 57.9%, respectively in Tiruvallur district. These results predict that infants and children from these three districts appear to be highly susceptible to non-carcinogenic nitrate and fluoride induced health hazards, while adults are predicted to be more or less immune to the associated health risks. [ABSTRACT FROM AUTHOR]

Perchlorate, one of the persistent inorganic pollutants, was efficiently removed from water using quaternary ammonium‐functionalized cross‐linked chitosan beads (QACB). This synthesized bead was found to be efficient in terms of perchlorate removal capacity, 100% regeneration of used beads (using HCl or NaCl) and selectivity in the presence of coanions, namely, chloride, sulfate, carbonate, and nitrate. QACB removes perchlorate by exchange of chloride ions. QACB was able to remove >95% perchlorate from brackish water. Batch studies were carried out in order to optimize the condition for maximum perchlorate removal. The perchlorate removal capacity of QACB from 1,000 mg/L of aqueous solutions was 153.0 mg/g. The outcome of pH variation studies indicated that QACB is able to remove perchlorate in the pH ranges of 2–11. Equilibrium isotherm data of adsorption of perchlorate at temperature 303, 313, and 323 K were well fitted to the linear Freundlich, Langmuir, and Dubinin–Radushkevich isotherm models. The adsorption kinetics data were best described by the pseudo‐second‐order kinetic model. FTIR was used to confirm the interaction of perchlorate with QACB. A small‐scale column test was carried out to evaluate the capacity of QACB for removing perchlorate from brackish water. [ABSTRACT FROM AUTHOR]

Chitosan beads cross-linked with glutaraldehyde were loaded with Zn(II) for the removal of nitrate and phosphate. The Zn(II) was bound by the free amino groups in the cross-linked chitosan beads. In order to utilise the hydroxyl groups on cross-linked chitosan, it was carboxylated with chloroacetic acid and then loaded with Zn(II). Both the sorbents viz. zinc-loaded cross-linked chitosan beads (ZnCB) and zinc-loaded carboxylated cross-linked chitosan beads (ZnCCB) were characterised by SEM, EDAX, X-ray diffraction and FT-IR. Adsorption studies were carried out in batch mode. The maximum adsorption capacity of ZnCB and ZnCCB for nitrate was 27.56 and 59.00 mg/g, respectively and for phosphate it was 31.45 and 67.50 mg/g, respectively. The suitability of the Freundlich, Langmuir and Dubinin–Radushkevich adsorption models to the adsorption equilibrium data was investigated. The equilibrium data obtained for nitrate and phosphate removal using ZnCCB were found to follow Freundlich adsorption isotherm. The thermodynamic parameters were evaluated. The results showed that the adsorption process was spontaneous, endothermic and entropy driven. [ABSTRACT FROM PUBLISHER]

Three different polymeric materials loaded with La(III) were prepared such as La(III)-loaded silica-chitosan composite (LSCC), an inorganic-organic hybrid material; La(III)-loaded cross-linked chitosan beads (LCB), a biopolymer; La(III)-loaded Duolite C 466 (LDR), a commercially available styrene divinyl benzene co polymer with imino diacetic acid and the adsorption behavior of phosphate on these three adsorbents were investigated in batch mode. The effects of contact time, temperature of solution, adsorbent dosage, initial pH of solutions, and coexistent anions were analyzed. The adsorption capacities of LSCC, LCB, and LDR from 1000 mg L−1 of phosphate solution were 155.4, 84.2, and 74.2 mg/g, respectively. Regenerations of the LSCC, LCB, and LDR were carried out with 0.25 M NaOH solution. All the three adsorbents were selective toward the phosphate ion in the presence of common ions like Cl−, NO3−, SO42−, and HCO3− present in natural water. The Freundlich isotherm model seems to be a better fit than the Langmuir and Dubinin-Radushkevich isotherm models. Thermodynamic parameters such as Δ G°, Δ H°, and Δ S° were calculated in order to understand the nature of adsorption process. The adsorption kinetics data were best described by the pseudo-second-order rate equation. The adsorbents were characterized using SEM with EDX, FTIR and BET surface area. © 2014 American Institute of Chemical Engineers Environ Prog, 34: 146-154, 2015 [ABSTRACT FROM AUTHOR]