Freeze–dried synthesized bifunctional biopolymer nanocomposite for efficient fluoride removal and antibacterial activity

Local fluoride contamination and bacterial infections in potable water have dangerous effects on the human body and are today a global concern. In this study, we have synthesized a pH-responsive bifunctional biopolymer nanocomposite (HAZ) of humic acid with incorporating aluminum zirconium bimetallic oxide by deep freeze–drying method. Fast nucleation and interconnection of nanoparticles form a highly porous network because of sublimation of frozen HAZ. This duo nanocomposite has efficiently worked for fluoride removal and showed potent antibacterial activity against the Escherichia coli Gram-negative and Staphylococcus aureus Gram-positive bacteria. The X-ray photoelectron spectroscopy (XPS) analysis demonstrates that the hydroxyl groups act as a pivot in the ion exchange process of adsorption, each element of bimetallic oxide primarily takes part in the adsorption mechanism. The maximum adsorption capacity of the adsorbent was 180.62 mg/g at pH seven. Thermodynamic parameters like Gibbs free energy change (ΔG⁰), entropy (ΔS⁰), and enthalpy (ΔH⁰) indicate that the process was endothermic, feasible, and taken place by a chemisorption mechanism. This is the first novel freeze–dried bifunctional biopolymer nanocomposite composed of humic acid natural polymer incorporated with Al–Zr metal oxide, and it exhibited three times higher adsorption efficacy with excellent antibacterial action at a concentration of 5 µg/mL of the nanocomposite.     

The chemical form of cobalt-60 in the marine sponge Spirastrella cuspidifera

The marine sponge Spirastrella cuspidifera Lamarck shows a remarkable capacity to concentrate cobalt-60 from its environment, the specific activity of the radionuclide being two orders of magnitude higher than that in the ambient water. This suggests a very slow equilibrium with stable cobalt. The chemical form of the deposited cobalt-60 has been investigated in S. cuspidifera collected from coastal waters in the vicinity of a nuclear power station. The majority of the cobalt-60, 75 to 85%, is readily extractable into distilled water. Chromatographic analysis of this soluble fraction shows that about 85% of the cobalt is present as a small-molecular weight complex of low stability. No binding to any specific protein could be identified. The possible mechanism for the preferential uptake of cobalt-60 by this species of sponge is discussed.     

Preliminary Report on Radon Concentration in Drinking Water and Indoor Air in Kenya

A screening survey has been carried out to determine activity concentrations of radon (²²²Rn) in drinking water and indoor air in various locations in Kenya. The concentration of ²²²Rn in water was measured using a liquid scintillation counter (LSC). Three different passive integrating devices were used in the measurements of ²²²Rn in air. In the short-term measurements, radon is absorbed in activated charcoal and the analyses were carried out using either LSC or gamma ray spectrometry. The long-term measurements were carried out using solid-state nuclear track detectors (SSNTD). The mean and maximum values of ²²²Rn concentrations in water are 37 and 410 Bq L^–1 and 100 and 1160 Bq m^–3, respectively, in air. The highest values were obtained from groundwater sources and in the basements of buildings. When these values are compared with the internationally recommended reference levels, there are indications of existence of radon problems in some of the water sources and the dwellings tested in this survey.     

Characterization of colloidal arsenic at two abandoned gold mine sites in Nova Scotia, Canada, using asymmetric flow-field flow fractionation-inductively coupled plasma mass spectrometry

Asymmetric flow-field flow fractionation-inductively-coupled plasma-mass spectrometry was used to determine whether colloidal arsenic(As) exists in soil pore water and soil extract samples at two arsenic-contaminated abandoned gold mines(Montague and Goldenville, Nova Scotia). Colloidal arsenic was found in 12 out of the 80 collected samples(= 15%), and was primarily associated with iron(Fe) in the encountered colloids. The molar Fe/As ratios indicate that the colloids in some samples appeared to be discrete iron–arsenic minerals, whereas in other samples, they were more consistent with As-rich iron(oxy)hydroxides. Up to three discrete size fractions of colloidal As were encountered in the samples, with mean colloid diameters between 6 and 14 nm. The pore water samples only contained one size fraction of As-bearing colloids(around 6 nm diameter), while larger As-bearing colloids were only encountered in soil extracts.     

Dissipation of flubendiamide in/on Brinjal (Solanum melongena) fruits

A field experiment was conducted at Anand Agricultural University, Anand during Sept-Dec, 2009 to study the rate of degradation of flubendiamide in/on brinjal fruits following foliar application of Fame 480 SC at 90 (standard dose) and 180 (double dose) g a.i. ha(?-1). The residues estimated using HPLC revealed persistence of flubendiamide in/on brinjal till 3rd and 7th day after the last spray at standard and double dose, respectively. The residues of flubendiamamde were reported as parent compound, and no desiodo metabolite was detected. The initial deposits of 0.17 and 0.42 μg g(?-1) in/on brinjal fruits reached below determination level of 0.05 μg g(?-1) on the 5th and 10th day at standard and double dose, respectively. The half life of flubendiamide on brinjal fruits ranged from 2.68 to 2.55 days. Soil samples analyzed on the 15th day after the last spray revealed residues at below determination level (0.05 μg g(?-1)) at either dose of application.     

Chromium speciation in a contaminated groundwater: redox processes and temporal variability

Chromium species (Cr(III), Cr(VI), and Cr(III)-organic) in groundwater of a tannery contaminated area were monitored during pre- and post-monsoon seasons for a period of 3 years (May 2004 to January 2007). The objectives of the study were (1) to investigate the temporal variation of chromium species and other matrix constituents and (2) to study the redox processes associated with the temporal variation of chromium species. Samples were collected from 15 dug wells and analyzed for chromium species and other constituents. The results showed that the groundwater was relatively more oxidizing during post-monsoon periods than the pre-monsoon periods. Except one sample, the concentration of chromium species were found in the order of Cr(VI)>Cr(III)>Cr(III)-organic complexes during all the pre- and post-monsoon periods. In most of the wells, the concentrations of Cr(III), Cr(VI), and Cr(III)-organic decreased during post-monsoon periods compared to their pre-monsoon concentrations. However, the Cr(VI)/Cr_Total ratio still increased and the Cr(III)/Cr_Total ratio decreased during post-monsoon periods in most of the samples. The possible mechanisms for the temporal variation of chromium species were (1) Fe(II) reduction of Cr(VI) vs oxidation of Fe(II) by dissolved oxygen and (2) oxidation of Cr(III) by Mn(IV).     

Removal efficiency of fluoride by novel Mg-Cr-Cl layered double hydroxide by batch process from water

The fluoride ion removal from aqueous solution using synthesized Mg-Cr-Cl layered double hydroxide has been reported.Mg-Cr-Cl was characterized by X-ray powder diffraction,Fourier-transform infrared,thermo-gravimetric analysis,differential thermal analysis,and scanning electron microscope.Adsorption experiments were carried out in batch mode as a function of adsorption dosages,contact time,pH,and initial fluoride concentration to get optimum adsorption capacity.The adsorption kinetic study showed that the adsorption process followed first order kinetics.The fluoride removal was 88.5% and 77.4% at pH 7 with an adsorbent dose of 0.6 g/100 mL solution and initial fluoride concentration of 10 mg/L and 100 mg/L,respectively.The equilibrium was established at 40 min.Adsorption experiment data were fitted well with Langmuir isotherm with R 2 = 0.9924.Thermodynamic constants were also measured and concluded that the adsorption process was spontaneous and endothermic in nature.The removal percentage decreased slowly with increasing pH.This process is suitable for industrial effluents.The regeneration of the material is not possible.     

A review on the urban municipal solid waste management system of an Indian Himalayan state

Journal of Material Cycles and Waste Management - Improper management of solid waste creates health problems and degrades the environment (air, water, and soil). The Indian state Uttarakhand is...