Recovery and reuse of Ni(II) from rinsewater of electroplating industries.

Discharge of nickel compounds, which may occur in both liquid and solid phases, can cause severe environmental problems. In this work, 'point of source' treatment strategy is followed and reduced the nickel content of rinsewater to about less than 1 mg L(-1) by ion-exchange method using a packed column involving batch recirculation mode of operation and to recovered Ni(II) content by desorption. The treated water could be recycled for rinsing operation. The nickel from resin is first precipitated as nickel hydroxide to synthesize positive active material and that was used in Nickel/Metal hydride cell. The performances in terms of electrochemical utilization of nickel hydroxide, specific capacity as a function of discharge current density and cycle life were examined and the nickel hydroxide electrode with 5% CaCO(3) addition, having 200 mAh g(-1) specific capacity, could be subjected to charge/discharge cycles at C/5 rate for more than 200 cycles without the capacity fading.

Production of biogas from municipal solid waste with domestic sewage.

In this study, experiments were conducted to investigate the production of biogas from municipal solid waste (MSW) and domestic sewage by using anaerobic digestion process. The batch type of reactor was operated at room temperature varying from 26 to 36 degrees C with a fixed hydraulic retention time (HRT) of 25 days. The digester was operated at different organic feeding rates of 0.5, 1.0, 2.3, 2.9, 3.5 and 4.3kg of volatile solids (VS)/m(3) of digester slurry per day. Biogas generation was enhanced by the addition of domestic sewage to MSW. The maximum biogas production of 0.36m(3)/kg of VS added per day occurred at the optimum organic feeding rate of 2.9kg of VS/m(3)/day. The maximum reduction of total solids (TS) (87.6%), VS (88.1%) and chemical oxygen demand (COD) (89.3%) occurred at the optimum organic loading rate of 2.9kg of VS/m(3)/day. The quality of biogas produced during anaerobic digestion process was 68-72%.

Surface ozone measurements at urban coastal site Chennai, in India.

The present study was carried out to gain knowledge of current surface ozone concentrations and the effects of meteorological parameters in the highly populated urban area of Chennai, in South India. We have reported measurement results of surface ozone (O(3)) and meteorological parameters from 17th March to 10th October 2005. A photometric ozone analyzer continuously recorded the ozone concentrations at this site. The present study deals with the statistical characteristics of daily and monthly mean ozone levels under different meteorological conditions. The highest ozone concentrations were recorded in ESE-SE sectors. The monthly mean concentrations were higher in May (23+/-14 ppb) and lower in April at this site (10+/-8 ppb). The maximum hourly ozone concentration reached 69 ppb on 21st April.

Equilibrium studies for the adsorption of acid dye onto modified hectorite.

The adsorption of Acid dye, C.I. Acid Red 151 from aqueous solution onto modified hectorite at different concentrations and pH has been studied. Hectorite clay has been modified using two cationic surfactants, cetyldimethylbenzylammonium chloride and cetylpyridinium chloride. Present experimental study shows that acidic pH favours enhanced adsorption. The adsorption isotherms are described by means of Langmuir and Freundlich isotherms. The adsorption capacity has been found to be 208.33 and 169.49 mg g(-1) for the modified cetyldimethylbenzylammonium chloride-hectorite (CDBA-hect) and cetylpyridinium chloride (CP-hect), respectively.

Air quality monitoring in Chennai, India, in the summer of 2005.

During the summer of 2005, concentrations of surface ozone (O(3)), oxides of nitrogen (NO(x)), respirrable suspended particulate matter (RSPM) and total suspended particulate matter (TSPM), relative humidity (RH), wind speed (WS) and wind direction (WD) were collected over successive periods of about 24 h at five sites. UV photometric ozone analyzer was used to measure the concentration of surface O(3). The study deals with the characteristics of hourly and daily mean surface O(3) under different climatic conditions, such as temperature, relative humidity, wind speed and wind direction and other pollutant concentrations. The maximum hourly O(3) concentration reached 53 ppb on 17th May. The ground-level O(3) concentration in Chennai varied between 2 and 53 ppb. The concentration of NO(x) and O(3) were below the prescribed limits. The TSPM values were exceeded the National Ambient Air Quality Standards (NAAQS) at Koyambedu, Mandaveli, Taramani and Vallalar Nagar study area.

Adsorption of acid dye onto organobentonite.

Removal of Acid Red 151 from aqueous solution at different dye concentrations, adsorbent doses and pH has been studied. The bentonite clay has been modified using cationic surfactants, which has been confirmed using XRD and FT-IR analyses. Experimental result has shown that the acidic pH favours the adsorption. The adsorption isotherms are described by means of Langmuir and Freundlich isotherms. The adsorption capacity has been found to be 357.14 and 416.66 mg g(-1) for the cetyldimethylbenzylammonium chloride-bentonite (CDBA-bent) and cetylpyridinium chloride-bentonite (CP-bent), respectively. Kinetic studies show that the adsorption followed second-order kinetics.

Modeling the mechanism involved during the sorption of methylene blue onto fly ash.

Batch sorption experiments were carried out to remove methylene blue from its aqueous solutions using fly ash as an adsorbent. Operating variables studied were initial dye concentration, fly ash mass, pH, and contact time. Maximum color removal was observed at a basic pH of 8. Equilibrium data were represented well by a Langmuir isotherm equation with a monolayer sorption capacity of 5.718 mg/g. Sorption data were fitted to both Lagergren first-order and pseudo-second-order kinetic models and the data were found to follow pseudo-second-order kinetics. Rate constants at different initial concentrations were estimated. The process mechanism was found to be complex, consisting of both surface adsorption and pore diffusion. The effective diffusion parameter D(i) values were estimated at different initial concentrations and the average value was determined to be 2.063 x 10(-9)cm2/s. Analysis of sorption data using a Boyd plot confirms the particle diffusion as the rate-limiting step for the dye concentration ranges studied in the present investigation (20 to 60 mg/L).