Studies on substituted phenols and triazolopyrimidine sulfonamide herbicide
Loading...
Date
2020-02
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
4-Nitrophenol and 2,4-dichlorophenol are two substituted phenols which are included in the priority pollutant list as chemical pollutants by United States Environmental protection agency (USEPA). The present study was undertaken to determine the utility of untreated and Fetreated Nostoc sp. as a potent biosorbent for the removal of these two phenols from wastewater. Adsorption –desorption, which is an efficient and cost effective method has been tried for removal of pollutants from wastewater. Thereafter, the kinetics of adsorption and effect of different state variables ( time, pH, concentration, ionic strength and temperature) on biosorption of phenols (4-NP and 2, 4-DCP) was conducted. The biosorbent (Nostoc sp.) was cultured in BG-11 medium and the dead dried biomass was obtained after filtration and drying. Part of this dried biomass was modified to Fetreated biomass by treatment with FeCl3(0.1 M ). The results obtained, suggested that the equilibration time for biosorption at different pH (4, 7, 9) was 12h with maximum sorption at pH 7 both on untreated and Fe treated biomass. Decrease in cumulative percent desorption from 11.25 to 0.47 for 4-NP and 1.83 to 0 percent for 2,4-DCP after treatment with iron showed the irreversibility of the biosorbent after iron treatment. Sorption data of phenols (4-NP and 2,4-DCP) was fitted to different models and pseudo second order kinetic model was found best with R2 value 0.999 (significant at p ≤ 0.01) in all the four cases (4-NP (untreated and Fe treated), 2,4-DCP (untreated and Fe treated). The effect of concentration was checked at four different concentrations (2, 4, 6 and 8 ppm) and the sorption data obtained fitted well to Freundlich adsorption isotherm indicating heterogeneous nature of binding sites on Nostoc. The Freundlich constants ln K and 1/n were also calculated and both were found to increase after treatment with iron for both the phenols. In order to see the effect of ionic strength two electrolytes ( CaCl2 and KCl at two concentrations were taken. Increase in ionic strength increased the biosorption of phenols probables due to the decreased thickness of the double diffused layer. Sorption studies at varying temperature (15, 25 and 35⁰C) revealed that increase in temperature decreased the biosorption indicating biosorption to be physical in nature. The FTIR investigation clearly revealed that functional groups like hydroxyl, aldehydic and nitro groups on the surface of the biosorbent were involved in the binding.SEM images of untreated and Fe treated Nostoc sp. showed elimination of cavities on the biosorbent surface after treatment with Fe3+ ions. Adsorption-desorption behaviour of penoxsulam in six different soils wasalso investigated under two state variables temperature and ionic strength. Physiochemical properties of soils were examined. pH showed strong correlation with adsorption of penoxsulam in soil. Among the six soils, three soils namely, LOH-5, HLD-1 and BH-1 were acidic in nature with pH below 6.5. Soil (HLD-2) was nearly neutral with pH 6.83 and two soils (BD-2 and JK-1) were basic with pH above 7.5. Adsorption in case of temperature and ionic strength was higher in acidic soils than in neutral and basic soils. Increase in temperature decreased the adsorption on each of the six soils, with maximum at 15⁰C followed by 25 and 35⁰C indicating adsorption to be physical in nature. Increase in ionic strength increased the adsorption which was significant at p≤ 0.05 in case of alkaline soils.The trends were attributed to the salting out phenomena.
Description
Keywords
null