NOPR Collection:

Sodium carbonate—From natural resources to Leblanc and back

2013-10-29T16:35:46Z

Title: Sodium carbonate—From natural resources to Leblanc and back Authors: Wisniak, Jaime Abstract: The development of sodium carbonate as a major commodity is intimately attached to the chemical revolution that took place in the eighteenth and nineteenth century. Strong political and economical reasons led to the search of synthetic procedures to replace the natural sources of soda that were available by the seventeenth century. Eventually Nicolas Leblanc developed a synthetic process that used common salt as raw material. Implementation of Leblanc’s procedure led to such serious environmental problems, e.g., acid rain, that the first laws for environmental protection were enacted in England. Treatment of the obnoxious gaseous, liquid, and solid wastes of the process resulted in new processes for the manufacture of chlorine and sulphur. Leblanc's process came to an end with the development of the Solvay process. Eventually, the discovery of huge fields of natural sodium carbonate in the U.S. led to the decline of the Solvay process. Page(s): 99-112

A simple sensitive spectrophotometric method for determination of dichlorvos in environmental samples

2013-10-28T16:37:11Z

Title: A simple sensitive spectrophotometric method for determination of dichlorvos in environmental samples Authors: Asthana, Anupama; Pillaia, Ajai; Gupta, V K Abstract: A sensitive method has been developed for spectrophotometric determination of an organophosphorous pesticide dichlorvos, also known as 2,2 dichlorovinyl methyl phosphate or dichlorophos. The method is based on hydrolysis of dichlorvos by sodium hydroxide to produce dichloroacetaldehyde, which on coupling with phloroglucinol in alkaline medium, gives orange colour. The orange dye shows absorption maxima at 475 nm and obeys Beer's law in the range of 10-100μg/25 mL (0.4 to 4 ppm) of solution. The molar absorptivity and Sandell's sensitivity were found to be 4.53×10⁴l mol^-1cm^-1 and 0.0048 μg cm^-2 respectively. The method has been successfully applied for the determination of dichlorvos in water, agricultural soil and vegetables. Page(s): 96-98

Removal of arsenic from water by coagulation treatment using iron and magnesium salt

2016-07-20T04:52:23Z

Title: Removal of arsenic from water by coagulation treatment using iron and magnesium salt Authors: Ghosh, B; Das, M C; Gangopadhyay, A K; Das, T B; Singh, K; Lal, S; Mitra, S; Ansari, S H; Goswami, T K; Chakraborty, S K; Banerjee, N N Abstract: Arsenic in ground water assumes a predicament of global dimension. Among the various methods of removal of arsenic from contaminated water, coagulation-filtration route has been examined in details covering effect of pH, coagulant type and its dose, and initial arsenic load in water. A set of batch experiments were conducted in the laboratory to investigate arsenic removal efficiency from spiked aqueous solution as well as a few ground water samples collected from the affected zone of West Bengal (India). The removal kinetics of aqueous arsenic spiked samples with iron/magnesium salt as coagulants were studied to assess the feasibility for the use in the arsenic removal in water treatment plant, and a plausible kinetic behaviour in their removal process has been discussed. A comparative performance efficiency for iron salt in contrast to magnesium salt as coagulant has been examined to establish the superiority of iron system. Increase in background ionic species such as Cl^ˉ, NO₃ˉ and SO^2-₄ in test solution with iron system have been performed in which Cl^ˉ and NO₃ˉ ions showed no effect on the efficiency of arsenic removal, while pronounced lowering effect has been observed in case of SO^2-₄ ion. This investigation suggests that for community supply of arsenic free water, the proposed protocol-coagulation with iron salt and subsequent filtration hold promise. Page(s): 87-95

TLC studies and separation of heavy metal cations on soil amended silica gel layers developed with surfactant-mediated solvent systems

2016-07-20T05:02:47Z

Title: TLC studies and separation of heavy metal cations on soil amended silica gel layers developed with surfactant-mediated solvent systems Authors: Mohammad, Ali; Jabeen, Nahed Abstract: Thin-layer chromatography (TLC) of ten heavy metal cations was performed on soil, silica gel and soil mixed with silica gel sorbent phases using aqueous solutions of cetyl trimethyl ammonium bromide (CTAB), sodium dodecyl sulphate (SDS), polyoxyethylene dodecyl ether (Brij-35) and iso-octylphenoxypolyethoxy ethanol (TX-100) surfactants with or without added urea, nitrate or chloride of ammonium and sodium phosphate as mobile phases. In all, twenty-nine stationary and twenty-five mobile phases were used in order to examine the mobility pattern and to find out the best TLC system for metal cations separation from their multicomponent mixtures on soil mixed with silica gel layers. The mobility of all cations was insignificant on pure soil layers irrespective of the nature of mobile phase used. Addition of silica gel into soil bed leads to the increase of mobility and facilitates the separation of metal cations. Amongst surfactant solutions, CTAB at concentration level of 0.5 M was found to be most effective, the analytical potentiality of which was further improved in the presence of urea. The TLC system comprising of silica gel plus 0.6 M urea (1:1,v/v) as mobile phase was found most favourable for achieving separations of metal ions from their multicomponent mixtures. A few such separations worth mentioning include, Fe³⁺-Cu²⁺-Ni²⁺-Hg²⁺, Zn²⁺-Cd²⁺-Hg²⁺, Ni²⁺-Cu²⁺-Fe³⁺, Zn²⁺-Fe³⁺-Ni²⁺-Hg²⁺, Pb²⁺-Cd²⁺-Hg²⁺ and Ni²⁺-Cu²⁺-Pb²⁺. R_F values of metal ions on soil amended with alumina, kieselguhr, cellulose and fly ash layers have also been determined. Salting - in effect exhibited by certain metal ions like Cd²⁺, Ni²⁺ or Co²⁺, Ag⁺, Hg²⁺ has been reported. Effect on mobility of metal ions, by replacing urea with different fertilizers in the CTAB containing mobile phase has also been examined. Page(s): 79-86