The use of low-cost adsorbent has been investigated as a replacement for the current expensive methods of removing dyes from wastewater. As such, fly ash generated in National Thermal Power plant was collected and converted into a low-cost adsorbent. The prepared adsorbent was characterized and used for the removal of dyes from wastewater. Adsorption studies were carried out for different temperatures, particle sizes, pH's, and adsorbent doses. The adsorption of each dye was found to increase with increasing temperature, thereby indicating that the process is endothermic in nature. The removal of each dye was found to be inversely proportional to the size of the fly ash particles, as expected. Both the linear and nonlinear forms of the Langmuir and Freundlich models fitted the adsorption data. The results indicate that the Freundlich adsorption isotherm fitted the data better than the Langmuir adsorption isotherm. Further, the data were better correlated with the nonlinear than the linear form of this equation. Thermodynamic parameters such as the free energies, enthalpies, and entropies of adsorption of the dye-fly ash systems were also evaluated. The negative values of free energy indicate the feasibility and spontaneous nature of the process, and the positive heats of enthalpy suggest the endothermic nature of the process. The adsorptions of crystal violet and basic fuschin follow first-order rate kinetics. In comparison to other low-cost adsorbents, the sorption capacity of the material under investigation is found to be comparable to that of other commercially available adsorbents used for the removal of cationic dyes from wastewater.
Despite pervasiveness of the market forces and supplementary role of the state and in some cases, even civil society organisations, there are unmet social needs which remain unaddressed by the existing institutions. With industrial growth becoming jobless, the need for new models of social innovation is being felt all around the world to provide jobs to the youth, skills for the new economy and entrepreneurial opportunities for transforming resources and skills. The persistence of some of these unmet needs (also referred as wicked problems sometimes) or unaddressed problems for a long time shows that the existing institutional arrangements are inadequate for the purpose. Innovations are imperative. A socio-ecological system that recognizes and rewards innovation can withstand many external shocks, provided it is agile and innovates quickly to remain responsive to emergent challenges (Anderies, Janssen, & Ostrom. Ecology and society, 9 (1)
Spent pot liner (SPL), a hazardous solid waste produced at cell houses of aluminum smelters, is a potential source of fluoride pollution. Leachates collected from SPL disposal sites were found to contain fluoride at considerable concentration levels (up to 575 mgIL). This paper reports a study of selective fluoride removal following laboratory-prepared, ion-exchange treatment. Spent pot liner leachates were pretreated with lime to bring the fluoride level down to approximately 10 mgIL for economic and effective working of the ion exchanger. The detailed ion-exchange treatment study for removal of fluoride was carried out on synthetic SPL leachates and the optimum treatment thus developed was applied on natural SPL leachates.Bench-scale studies were carried out at various flow rates and pHs and in the presence of other ions commonly available in the SPL leachates. The prepared exchanger reduced the level of fluoride from approximately 10 mglL to less than I mgIL. Results indicate that the extraction was 100% up to 6-mUmin flow rate through the ion exchanger and it works efficiently in the pH range of 7 to 10. There is no effect of the other ions present in leachates on removal of fluoride. The exchanger has good capacity to exchange and can be recharged by eluting fluoride sorbed on the exchanger using two molar hydrochloric acid. Water Environ. Res., 71,36 (1999).
Two new iridoids 6-O-[2,3-dimethoxy]-trans-cinnamoyl catalpol (1) and 6-O-meta-methoxy-benzoyl catalpol (2) along with a known iridoid picroside 1 (3), two stilbenes quadrangularin A (4) and pallidol (5), quercitin (6), quercitrin (7), beta-sitosterol (8) and beta-sitosterol glycoside (9) were isolated from Cissus quadrangularis Linn. The compounds 3 and 7 are first reported from this plant. The structures were elucidated by analysis of their spectroscopic data and by direct comparison with literature. This is the first reported occurrence of iridoids in C. quadrangularis.
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