K. Palanivelu

Preconcentration and separation of copper, nickel and zinc in aqueous samples by flame atomic absorption spectrometry after column solid-phase extraction onto MWCNTs impregnated with D2EHPA-TOPO mixture.

A solid phase extraction method has been developed for the determination of copper, nickel and zinc ions in natural water samples. This method is based on the adsorption of copper, nickel and zinc on multiwalled carbon nanotubes (MWCNTs) impregnated with di-(2-ethyl hexyl phosphoric acid) (D2EHPA) and tri-n-octyl phosphine oxide (TOPO). The influence of parameters such as pH of the aqueous solution, amount of adsorbent, flow rates of the sample and eluent, matrix effects and D2EHPA-TOPO concentration have been investigated. Desorption studies have been carried out with 2 mol L(-1) HNO(3). The copper, nickel and zinc concentrations were determined by flame atomic absorption spectrometry. The results indicated that the maximum adsorption of copper, nickel and zinc is at pH 5.0 with 500 mg of MWCNTs. The detection limits by three sigma were 50 μg L(-1) for copper, 40 μg L(-1) for nickel and 60 μg L(-1) zinc. The highest enrichment factors were found to be 25. The adsorption capacity of MWCNTs-D2EHPA-TOPO was found to be 4.90 mg g(-1) for copper, 4.78 mg g(-1) for nickel and 4.82 mg g(-1) for zinc. The developed method was applied for the determination of copper, nickel and zinc in electroplating wastewater and real water sample with satisfactory results (R.S.D.s <10%).

Copper removal from aqueous solution by marine green alga Ulva reticulata

The batch removal of copper (II) ions from aqueous solution under different experimental conditions using Ulva reticulata was investigated in this study. The copper (II) uptake was dependent on initial pH and initial copper concentration, with pH 5.5 being the optimum value. The equilibrium data were fitted using Langmuir and Freundlich isotherm model, with the maximum copper (II) uptake of 74.63 mg/g determined at a pH of 5.5. The Freundlich model regression resulted in high correlation coefficients and the model parameters were largely dependent on initial solution pH. At various initial copper (II) concentrations (250 to 1000 mg/L), sorption equilibrium was attained between 30 and 120 min. The copper (II) uptake by U. reticulata was best described by Pseudo-second order rate model and the rate constant, the initial sorption rate and the equilibrium sorption capacity were also reported. The elution efficiency for copper-desorption from U. reticulata was determined for 0.1 M HCl, H 2 SO 4 , HNO 3 and CaCl 2 at various Solid-to-Liquid ratios (S/L). The solution CaCl 2 (0.1 M) in HCl at pH 3 was chosen to be the most suitable copper-desorbing agent. The biomass was also employed in three sorption-desorption cycles with 0.1 M CaCl 2 (in HCl, pH 3) as the elutant.

Assessment of heavy metal species in decomposed municipal solid waste

Abstract Heavy metal speciation studies on municipal solid waste samples collected from Kodungaiyur dumpsite in Chennai, India, were carried out for Cu, Ni, Pb, Zn, Cr, Fe, Mn and Cd. Three samples were collected at depths of 0-1 m, 1-2 m and 2-3 m, and analyzed. X-ray diffraction studies showed the presence of montmorillonite, illite, quartz and calcium carbonate minerals. The Tessier method was used to fractionate the metal content into exchangeable, acid extractable, reducible and oxidizable fractions. Residual and total metal contents were determined in the aqua regia digest. Iron was the major metal constituent (20g kg-1) while the lowest metal concentration was found for cadmium (3mg kg-1). Descending order of the average total metal contents for these three depth levels was Fe, Cu, Zn, Cr, Mn, Pb, Ni and Cd. The bioavailable fraction (exchangeable and acid extractable fractions) comprised less than 40% of the total metal content for all the metals studied, except Cd. Most of the Fe and Cr were found to be associated with the residual fraction, which is almost inert. Based on the average of absolute values for the three depth levels, the bioavailability order of metals is Zn>Mn>Pb>Ni>Cu>Fe>Cr>Cd. Recovery obtained by comparing the aqua regia extracted metal content with the sum of sequentially extracted fractions was in the range of 91-110%.

Nickel Recovery from Aqueous Solution Using Crab Shell Particles

The potential use of crab shell as a sorbent for the removal of nickel(II) ions from aqueous solution was investigated. The binding of nickel ions by crab shell was found to be affected significantly by pH, with the maximum sorption capacity being observed at pH 4.5. The sorption isotherm was well represented using the Freundlich model. Nickel(II) ion removal by crab shell was mainly influenced by the removal of calcium carbonate, proteins and chitin, indicating the importance of these components in nickel ion binding. Co-ions such as Cu2+, Co2+, Cd2+, Zn2+ and Mg2+ affected the Ni(II) ion removal efficiency of crab shell. The biosorbed Ni(II) ions were effectively eluted by various mineral acids, EDTA solutions and NH4OH. Of these, the sodium salt of EDTA (0.01 M) in NH4OH appeared to be the best eluant, being capable of desorbing more than 99% of the sequestered Ni(II) ions with insignificant damage to the shell particles. The biosorbent could be regenerated and re-used in five sorption—elution cycles.

Climate Change Mitigation via Utilization of Carbon Dioxide

Carbon dioxide is a waste product in many industries, especially from thermal power plants and is a major contributor to global warming. The large scale solution to the problem of CO2 emissions currently being considered is carbon capture and storage (CCS). In CCS, the CO2 is first separated from the flue gas by capture techniques and then later stored underground. This method does not eliminate CO2; it just stores it. Environmental threats of escape are spurring re-evaluation of CCS to eliminate CO2 rather than move and store it. A more attractive solution would be carbon capture and utilization (CCU) in which the waste CO2 is not dumped, but converted into a commercially valuable product. The growing re-evaluation of carbon capture strategies emphasizes transforming CO2 to valuable chemical rather than storing it. This chapter gives an overview to cover the work carried out on CO2 from flue gas, and how it could be converted into a valuable chemical for which there is a demand. This article first covers briefly the CO2 separation or capture from flue gas and storage and then the technologies to convert the separated CO2 into usable chemicals employing methods, such as chemical, photochemical, electro-chemical and bio-process. The proper use of CO2 from waste flue gas is expected to provide both environmental and economic benefits.

Climate change projections over India by a downscaling approach using PRECIS

This study presents a comprehensive assessment of the possible regional climate change over India by using Providing REgional Climates for Impacts Studies (PRECIS), a regional climate model (RCM) developed by Met Office Hadley Centre in the United Kingdom. The lateral boundary data for the simulations were taken from a sub-set of six members sampled from the Hadley Centre’s 17- member Quantified Uncertainty in Model Projections (QUMP) perturbed physics ensemble. The model was run with 25 km × 25 km resolution from the global climate model (GCM) - HadCM3Q at the emission rate of special report on emission scenarios (SRES) A1B scenarios. Based on the model performance, six member ensembles running over a period of 1970-2100 in each experiment were utilized to predict possible range of variations in the future projections for the periods 2020s (2005-2035), 2050s (2035-2065) and 2080s (2065-2095) with respect to the baseline period (1975-2005). The analyses concentrated on maximum temperature, minimum temperature and rainfall over the region. For the whole India, the projections of maximum temperature from all the six models showed an increase within the range 2.5°C to 4.4°C by end of the century with respect to the present day climate simulations. The annual rainfall projections from all the six models indicated a general increase in rainfall being within the range 15-24%. Mann-Kendall trend test was run on time series data of temperatures and rainfall for the whole India and the results from some of the ensemble members indicated significant increasing trends. Such high resolution climate change information may be useful for the researchers to study the future impacts of climate change in terms of extreme events like floods and droughts and formulate various adaptation strategies for the society to cope with future climate change.

Erratum to: Climate change projections over India by a downscaling approach using PRECIS

The author “Bhaski Bhaskaran” and his affiliation “Fujitsu Laboratory of Europe, Middlesex, UK” should be replaced by “Balakrishnan Bhaskaran”, “Fujitsu Laboratories of Europe Limited, Hayes Park, Middlesex, UK”, respectively.The corrected name and affiliation are shown in this erratum.