Mine Özdemir

DISSOLUTION KINETICS OF SEPIOLITE IN HYDROCHLORIC ACID AND NITRIC ACID

The dissolution kinetics of sepiolite in hydrochloric acid and nitric acid were studied in a batch reactor. The effects of reaction temperature, acid concentration, particle size and solid-to-liquid ratio on the dissolution process were investigated. Experimental studies were carried out in the ranges of 25–75°C for reaction temperature, 0.25–1.00 mol/L for acid concentration, 0.00755–0.05020 cm for average particle size and 2.5 to 12.5 g of solid/100 mL of acid for solid-to-liquid ratio. It was determined that the dissolution process is controlled by resistance of the diffusion through the product layer. The activation energies of the process were determined to be 40.8 and 38.3 kJ/mol for hydrochloric and nitric acid, respectively. The apparent rate constants were expressed as a function of reaction temperature, acid concentration, particle radius and solid-to-liquid ratio: kαe−4910(1/T)Cr−0.6 (s/l)−1 and kαe−4606(1/T)Cr−0.5 (s/1)−1 for hydrochloric and nitric acid, respectively; k is the apparent rate constant in min−1; T, the reaction temperature (K); C, the acid concentration (mol/L); r, the initial particle radius (cm); s/l, the solid-to-liquid ratio (g of solid/100 mL of acid).

Removal of nickel from aqueous solution using magnesite tailing

The removal of nickel ions from aqueous solutions using magnesite tailing was studied in batch system. The effects of initial pH, adsorbent dosage, contact time, and temperature on nickel removal were investigated. Kinetic models were evaluated to describe the kinetics of nickel adsorption onto magnesite tailing. The adsorption kinetics conformed to the pseudo-second-order kinetic model. The Langmuir and Freundlich models were used for the analysis of adsorption equilibrium. The equilibrium data obeyed the Langmuir isotherm model. The thermodynamic parameters exhibited that the adsorption process was spontaneous and endothermic. The Fourier transform infrared spectroscopy analysis was applied to characterize the unloaded and nickel-loaded magnesite tailing. The functional groups such as hydroxyl, carbonate, silicon oxide, and iron oxide on the adsorbent surface may be responsible for nickel adsorption.

Recovery of Boron from the Clay Waste of Boron Industry by Leaching

Abstract In this study, the recovery of boron from the clay waste of boron industry by leaching with sulfuric acid solution was studied in a batch reactor and the subsequent production of boric acid (H3BO3) was investigated. The effects of acid concentration, solid-to-liquid ratio and reaction temperature on the leaching process were examined. Experimental studies were carried out in the ranges of 0.1-1.0 M for acid concentration, 1-10 g/120 mL for solid-to-liquid ratio and 25-75°C for reaction temperature. The analysis of the experimental data showed that the kinetics of the leaching process fitted the Avrami model in the form of X = 1 – exp (–k t n). For the production of boric acid, the optimum leaching conditions were determined as follows: acid concentration, 0.1 M; solid-to-liquid ratio, 6 g/120 mL; reaction temperature, 50°C and reaction time, 60 min. Finally, boric acid was produced in the purity of more than 95% by crystallization of the leach solution.

Talaromyces aculeatus from acidic environment as a new fungal biosorbent for removal of some reactive textile dyes

Biosorption potential of Talaromayces aculeatus AMDC-14 (KF588645) as low-cost biosorbent for different dyes (Reactive Blue 13, Reactive Blue 72, Reactive Yellow 85 and Reactive Orange 13) removal from aqueous medium was studied. Experiments were performed to determine effect of initial solution pH (1-7), biosorbent dose (0.1-2.5 g L -1 ), time (15-1440 min), dye concentration (10-200 ppm) and temperature (25-40 °C) onto Talaromayces aculeatus biosorption . Biosorption equilibrium data were described very well for Reactive Blue 13, Reactive Blue 72, Reactive Yellow 85 and Reactive Orange 13 by Langmuir isotherm model than Freundlich isotherm model with maximum biosorption capacities which are 32.10, 71.30, 20.67 and 31.30 mg g -1 , respectively. Biosorption of investigated dyes fitted to kinetic model of pseudo-second-order for all dyes. Gibbs free energies (ΔG°) of biosorption processes were calculated and the results indicated that all selected dyes biosorption onto Talaromayces aculeatus AMDC-14 were spontaneous in this study. And also biosorption processes had endothermic enthalpy values except Reactive Blue 72.