Extraction of Scandium (III) from acidic solutions using organo-phosphoric acid reagents: A comparative study

Comparative and synergistic solvent extraction of Sc(III) using two phosphoric acidic reagents such as di-(2-ethyhexyl) phosphoric acid and 2,4,4,tri-methyl,pentyl-phosphinic acid was investigated. Slope analysis method suggests a cation exchange reaction of Sc(III) with both extractants at a molar ratio of extractant: Sc(III) = 2.5:1 at equilibrium pH< 1.5. The plot of log D vs. log [Extractant] yield the slope (n) value as low as 1.2-1.3 and as high as n=7 at low and high extrcatant concentration level, respectively. Extraction isotherm study predicted the need of 2 stages at A: O=1:4 and A: O=1:3 using 0.1 M D2EHPA and 0.1 M Cyanex 272, respectively. Stripping of Sc (III) was carried out at varied NaOH concentration to ascertain the optimum stripping condition for effective enrichment of metal. The predicted stripping condition (2)-stages with A: O=1:3 and 1:4 for D2EHPA and Cyanex 272, respectively) obtained from Mc-Cabe Thiele plot was further validated by 6-cycles CCS study. An actual leach solution of Mg-Sc alloy bearing 1.0 g/L of Sc (III), 2.5 g/L of Mg and 0.2 M HCl was subjected for selective separation of Sc at the optimum condition. The counter current simulation (CCS) study for both extraction and stripping of actual solution resulted quantitative separation of Sc with ∼12 fold enrichment. The organic phase before and after loading of Sc (III) along with the diluents was characterized by FTIR to ascertain the phase transportation of Sc (III)

Extensive investigation on the study for the adsorption of Bromocresol Green (BCG) dye using activated Phragmites karka

Removal of Bromocresol green (BCG) dye from aqueous solution has been investigated using activated bio-sorbent Phragmites karka (PK). Batch adsorption method has been adopted and different parameters such as; pH of the solution, contact time, agitation speed, APK/BCG dose and temperature has been studied. From the resulted adsorption data the process is optimised and the transportation mechanism of BCG onto APK phase is proposed. In this study the bio-adsorbent PK is charred using H2SO4 to produce activated Phragmites karka (APK) which appears as an effective adsorbent on enhancing the loading efficiency of BCG than PK without activation. The BCG adsorption efficiency is increased from 16.05 to 84.2 % with increasing in acidity of the solution and maximized at pH 0.5 of solution. Maximum loading capacity of 392.3 mg/g is resulted using APK as adsorbent while removing BCG at ambient condition. The PK, APK, BCG loaded APK, and BCG are characterized by SEM, UV-vis and FTIR to ascertain the adsorption process as well as mechanism. The absorption peak obtained at 3450 cm-1 due to ν (O-Hstr) of BCG was shifted to a broad band at 3270 cm-1 shows the conjugation of BCG on surface of the APK, confirming the transporation of BCG to APK Phase as resulted from FTIR analysis. From the adsorption kinetics study, the rate of BCG adsorption shows well fit to the pseudo second order model than pseudo first order kinetic model. The positive value of, ∆Ho 2.49 kJ/ mole obtained by thermodynamic study reveals the endothermic nature of adsorption and and ∆So 24.87 J.K-1mol-1 shows the increase in degrees of freedom of BCG during adsorption. Equilibrium data are analysed by Langmuir, Freundlich and Tempkins adsorption isotherm to establish adsorption mechanism and the results shows best fit with Freundlich (R2=0.99) isotherm and reveals that the adsorption is of chemisorptions type