Efficient removal of crystal violet dye from industrial wastewater using Fe3+ coated biochar
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Date
2022-08
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G.B. Pant University of Agriculture and Technology, Pantnagar, District Udham Singh Nagar, Uttarakhand. PIN - 263145
Abstract
Crystal violet (CV), a cationic triarylmethane group is one of the most commonly used synthetic dye for purple coloration in aqueous solutions. CV is used in the production of black and blue inks for ballpoint pens, printer ink jet manufacturing industries etc. CV, like most dyes, is toxic and carcinogenic with an obstinate classification. In this research study, we used Fetreated PNB for the removal of CV dye from industrial wastewater. The effects of concentration, pH, ionic strength, temperature on adsorption–desorption behavior of this dye were seen. Ion exchange studies were also performed using CH3COOH. The results suggested that the equilibration time of adsorption of CV dye onto Fe-treated and untreated biochar was 24 hours both at pH 7.0 and 9.2, with maximum dye adsorption at pH 7.0. Pseudo-first order kinetics fit well to the adsorption kinetics of CV dye onto untreated and Fe-treated biochar, with R2 values
of 0.959 for Fe-treated biochar at pH 9.2 and 0.995 for untreated biochar at pH 7.0; all significant at p ≤0.001 and the lowest SEest value. At both pH levels, the quantity of CV dye adsorbed increased with increasing initial concentration for Fe-treated and untreated biochar. The adsorption data of CV onto untreated and Fe-treated biochar at equllibrium pH 7.0 and untreated biochar at pH 9.2 fit well to the to the Freundlich adsorption isotherm (R2= 0.877, significant at p ≤ 0.05 to 0.946, significant at p ≤ 0.01). However, the R2 value for Fe-treated biochar at equilibrium pH 9.2 was 0.746, which was statistically insignificant at p≤ 0.05. Third degree polynomial connections adequately described desorption data (R2= 0.987 to 0.998, all significant at p ≤ 0.01). The adsorption of CV dye onto treated and untreated biochars was significantly increased by increasing the ionic strength from 0.003 to 0.03 and decreased on increasing ionic strength from 0.03 to 0.3. The rise in temperature above 35 ˚C for untreated biochar at pH 7.0 and beyond 25 ˚C at pH 9.2 was statistically insignificant. Similarly, the amount of the relative increase in CV adsorption with temperature increase from 5 to 15 ˚C and from 25 to 45 ˚C for Fe-treated biochar at pH 7.0 was not statistically significant. At pH 9.2, the relative increase in CV adsorption by Fe-treated biochar with temperature rise from 5 to 15 ˚C was statistically insignificant. FTIR spectra revealed the presence of –OH and >C=O on the surface of untreated biochar, as well as certain oxyhydroxide minerals of Fe in Fe-treated biochars. Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) analysis revealed the heterogeneous and porous structure of untreated biochar. Fe was seen to accumulate as polymerized hydroxy species in Fe-treated biochar. At pH 7.0, a substantial dye deposit was seen in dye-loaded treated biochar. There was some disintegration of untreated biochar surface and separation of Fe hydroxy compounds from treated biochar at pH 9.2. EDS approach was used to determine the percentage of each element in various biochars. Untreated biochars had substantial concentrations of C, O, Mg, K, and Ca, whereas Fe-treated biochars contained considerable amounts of Fe, Ag, Si, and trace amounts of Ca.