Response surface modeling for optimization heterocatalytic Fenton oxidation of persistence organic pollution in high total dissolved solid containing wastewater

The rice-husk-based mesoporous activated carbon (MAC) used in this study was precarbonized and activated using phosphoric acid. N₂ adsorption/desorption isotherm, X-ray powder diffraction, electron spin resonance, X-ray photoelectron spectroscopy and scanning electron microscopy, transmission electron microscopy, ²⁹Si-NMR spectroscopy, and diffuse reflectance spectroscopy were used to characterize the MAC. The tannery wastewater carrying high total dissolved solids (TDS) discharged from leather industry lacks biodegradability despite the presence of dissolved protein. This paper demonstrates the application of free electron-rich MAC as heterogeneous catalyst along with Fenton reagent for the oxidation of persistence organic compounds in high TDS wastewater. The heterogeneous Fenton oxidation of the pretreated wastewater at optimum pH (3.5), H₂O₂ (4 mmol/L), FeSO₄?7H₂O (0.2 mmol/L), and time (4 h) removed chemical oxygen demand, biochemical oxygen demand, total organic carbon and dissolved protein by 86, 91, 83, and 90 %, respectively.     

Eco-friendly approach for leaching out heavy metals from sewage sludge

Sewage sludge contains rich organic matter and nutrients essential for the growth of plants but the presence of toxic heavy metals restricts its land application. To overcome this, the study aims an eco-friendly approach for leaching out heavy metals. Sewage sludge from sewage treatment plant, Chennai, India was characterised. The analysis of total heavy metal concentration was done by digesting in nitric acid and different forms were extracted by community bureau of reference sequential method. Heavy metals: As, Cd, Cr, Cr, Ni, Pb and Zn were determined using inductively coupled plasma optical emission spectrometry Perkin Elmer Optima 5300 DV. The experimental set-up for heavy metal leaching was held for five consecutive days at different concentrations of humic acid (0.1%, 0.5% and 1%) at varied pH (5–9). Results revealed that at the end of fifth day at pH 8, 1% humic acid is capable of leaching out 75.5% cadmium, 66.0% nickel, 52.0% lead, 51.2% zinc, 31.2% copper and 8.5% cadmium from sewage sludge. Statistically positive correlation (0.7088) existed between the percentage of heavy metals leached out and the sum of soluble and reducible fractions. Thus, from ecological point of view, humic acid can be used to leach out heavy metals from sewage sludge serving the need in restoration of soil fertility upon land application.     

The validity of situational interviews for administrative jobs

This study was conducted to determine the validity of situational interviews for making predictions of ratings of job performance and potential. The validation sample consisted of 63 candidates. The correlations of potential and performance with situational interview scores were statistically significant and both predictor and criterion measures showed acceptable levels of reliability. The study provides additional evidence on the validity of situational interviews in a new job family, i.e. administrative jobs in a large U.K. financial services organization. The discussion questions the extent to which situational interviews provide unique or overlapping predictive validity when compared with mental ability tests.     

Adsorption of ammonium ion by coconut shell-activated carbon from aqueous solution: kinetic, isotherm, and thermodynamic studies

Ammonium ions are one of the most encountered nitrogen species in polluted water bodies. High level of ammonium ion in aqueous solution imparts unpleasant taste and odor problems, which can interfere with the life of aquatics and human population when discharged. Many chemical methods are developed and being used for removal of ammonium ion from aqueous solution. Among various techniques, adsorption was found to be the most feasible and environmentally friendly with the use of natural-activated adsorbents. Hence, in this study, coconut shell-activated carbon (CSAC) was prepared and used for the removal of ammonium ion by adsorption techniques. Ammonium chloride (analytical grade) was purchased from Merck Chemicals for adsorption studies. The CSAC was used to adsorb ammonium ions under stirring at 100 rpm, using orbital shaker in batch experiments. The concentration of ammonium ion was estimated by ammonia distillate, using a Buchi distillation unit. The influence of process parameters such as pH, temperature, and contact time was studied for adsorption of ammonium ion, and kinetic, isotherm models were validated to understand the mechanism of adsorption of ammonium ion by CSAC. Thermodynamic properties such as ?G, ?H, and ?S were determined for the ammonium adsorption, using van't Hoff equation. Further, the adsorption of ammonium ion was confirmed through instrumental analyses such as SEM, XRD, and FTIR. The optimum conditions for the effective adsorption of ammonium ion onto CSAC were found to be pH 9.0, temperature 283 K, and contact time 120 min. The experimental data was best followed by pseudosecond order equation, and the adsorption isotherm model obeyed the Freundlich isotherm. This explains the ammonium ion adsorption onto CSAC which was a multilayer adsorption with intraparticle diffusion. Negative enthalpy confirmed that this adsorption process was exothermic. The instrumental analyses confirmed the adsorption of ammonium ion onto CSAC.     

Preparation of light weight constructional materials from chrome containing buffing dust solid waste generated in leather industry

Journal of Material Cycles and Waste Management - An alternative and environmentally benign method of disposing the buffing dust, generated from leather industry was carried out in the present...     

Heterocatalytic Fenton oxidation process for the treatment of tannery effluent: kinetic and thermodynamic studies

Background, aim, scope

Treatment of wastewater has become significant with the declining water resources. The presence of recalcitrant organics is the major issue in meeting the pollution control board norms in India. The theme of the present investigation was on partial or complete removal of pollutants or their transformation into less toxic and more biodegradable products by heterogeneous Fenton oxidation process using mesoporous activated carbon (MAC) as the catalyst.

Materials and methods

Ferrous sulfate (FeSO₄·7H₂O), sulfuric acid (36?N, specific gravity 1.81, 98% purity), hydrogen peroxide (50% v/v) and all other chemicals used in this study were of analytical grade (Merck). Two reactors, each of height 50?cm and diameter 6?cm, were fabricated with PVC while one reactor was packed with MAC of mass 150?g and other without MAC served as control.

Results and discussion

The oxidation process was presented with kinetic and thermodynamic constants for the removal of COD, BOD, and TOC from the wastewater. The activation energy (Ea) for homogeneous and heterogeneous Fenton oxidation processes were 44.79 and 25.89?kJ/mol, respectively. The thermodynamic parameters ??G, ??H, and ??S were calculated for the oxidation processes using Van??t Hoff equation. Furthermore, the degradation of organics was confirmed through FTIR and UV?Cvisible spectroscopy, and cyclic voltammetry.

Conclusions

The heterocatalytic Fenton oxidation process efficiently increased the biodegradability index (BOD/COD) of the tannery effluent. The optimized conditions for the heterocatalytic Fenton oxidation of organics in tannery effluent were pH 3.5, reaction time?C4?h, and H₂O₂/FeSO₄·7H₂O in the molar ratio of 2:1.     

Monitoring of cellular enzymes in the serum of electroplating workers at Coimbatore

Chromium compounds are potent toxic and carcinogenic substances. With respect to toxicity, hepatic and renal toxicity have been reported both in workers and in animals exposed to chromium (VI). Chromium (VI) compounds induces DNA damage in vivo and in cultured cells as well as the cytotoxicity evaluated by the leakage of lactate dehydrogenase. The present study reports the cytotoxicity of chrome platers who are employed from 8 to 25 years in electroplating industries at Coimbatore, Tamilnadu. Blood samples were collected and estimated for glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), alkaline phosphatase (ALP), lactate dehydrogenase (LDH), creatine phosphokinase (CPK) and total protein in the serum. The study revealed that there is a significant elevation in the level of LDH, ALP, CPK and transaminases and a decrease in total protein in serum. The results of the study suggests that chromium (VI), a hepatotoxic chemical may perhaps damage the plasma membrane resulting in leakage of enzymes in to the serum of chromeplaters.