Shiva Agarwal

Removal of lindane and malathion from wastewater using bagasse fly ash—a sugar industry waste

The bagasse fly ash, obtained from the local sugar industry, has been used as inexpensive and effective adsorbent for the removal of lindane and malathion from wastewater. The optimum contact needed to reach equilibrium was found to be 60 min. Maximum removal takes place at pH 6.0. The removal of the pesticides increases with an increase in adsorbent dose and decreases with adsorbent particle size. The optimum adsorbent dose is 5 g/l of particle size 200-250 microm. Removal of the two pesticides was achieved up to 97-98% under optimum conditions. The material exhibits good adsorption capacity and follows both Langmuir and Freundlich models. Thermodynamic parameters also indicate the feasibility of the process. The adsorption was found to be exothermic in nature. At lower concentrations, adsorption is controlled by film diffusion, while at higher concentrations, it is controlled by particle diffusion mechanisms. The adsorbent is a very useful and economic product for the removal of lindane and malathion.

A copper-selective electrode based on bis(acetylacetone)propylenediimine

The potentiometric response characteristics of Cu(2+)-selective electrodes based on bis(acetylacetone)propylenediimine (I) combined with anion localizing agent (sodium tetraphenyl borate (NaTPB)) and solvent mediators (dibutyl butyl phosphonate (DBBP), tri-n-butyl phosphate (TBP) and chloronaphthalene (CN)) were investigated. The best results for Cu(2+) sensing was obtained for the electrode membrane containing PVC, I, DBBP and NaTPB in composition 5:100:200:6 (I:PVC:DBBP:NaTPB) (w/w; mg), where the electrode had a Nernstian response (30.0mV/decade) to Cu(2+) within the concentration range 1.0x10(-5) to 1.0x10(-1)M and detection limit of 0.5ppm. The operational pH range of the electrode was 3.3-7.0. Selectivity characteristic of the proposed electrode was also assessed by calculating K(A,B)(Pot) using fixed interference method matched potential method. The sensor has been successfully used in the potentiometric titration of copper ions with EDTA.

PVC based 5,10,15,20-tetrakis (4-methoxyphenyl) porphyrinatocobalt(II) membrane potentiometric sensor for arsenite

PVC based membranes of 5,10,15,20-tetrakis(4-methoxyphenyl)porphyrinatocobalt(II) (TMOPP-Co) (I) as electroactive material with dibutyl butyl phosphonate (DBBP), dioctyl phthalate (DOP), 1-chloronaphthalene (CN), tri-n-butyl phosphate (TBP) and tris(2-ethylhexyl) phosphate (TEP) as plasticising solvent mediators have been prepared and tried for arsenite determination. The membrane having a composition 150:5:150 (PVC:I:DBBP) exhibited the best results with linear potential response in the concentration range of 7.9 x 10(-5) to 1.0 x 10(-1)M of AsO(2)(-) with a slope of 28.8mV/decade. The useful pH range of the sensor is 6.0-10.5. The membrane worked satisfactorily in non-aqueous medium up to 5% (v/v) non-aqueous content. The selectivity coefficient values for mono- and divalent anions indicate good selectivity for arsenite over a large number of anions.

Nickel(II)-selective sensor based on dibenzo-18-crown-6 in PVC matrix.

Nickel(II)-selective sensors have been fabricated from poly(vinyl chloride) (PVC) matrix membranes containing neutral carrier dibenzo-18-crown-6 as electroactive material, sodium tetraphenylborate (NaTPB) as an anion excluder and tris-(2-ethylhexyl) phosphate (TEHP) as plasticizing solvent mediator. The membrane having the composition of crown ether:NaTPB:TEHP:PVC in the ratio 10:1:200:200 (w/w) exhibits best results with linear potential response in the concentration range of 1.0x10(-5) to 1.0x10(-1)M and a Nernstian slope of 29.5mV/decade of activity between 2.6 and 6.8. The sensor exhibits a fast response time of <25s, is inert towards non-aqueous medium up to 15% (v/v) and was used over a period of 4 months with good reproducibility. It is selective over a number of mono-, bi- and trivalent cations. The practical utility of the sensor has been demonstrated by using it as an indicator electrode in the potentiometric titration of Ni(2+) against EDTA and also for the estimation of Ni(2+) in some Indian brand chocolates.