The dissolution kinetics of colemanite in phosphoric acid solutions was studied. The effects of particle size, temperature, acid concentration, solid-to-liquid ratio, and stirring speed on the dissolution rate were determined. It was observed that the dissolution rate increased with decreasing particle size and solid-to-liquid ratio and with increasing temperature, but stirring speed had no effect on it. The dissolution rate increased up to an acid concentration of 19.52% (by wt) and then decreased with increasing acid concentration. The dissolution kinetics of colemanite were examined according to the heterogeneous and homogeneous reaction models for the acid concentration range of 1.43−19.52% (by wt) of acid concentration, and it was found that the dissolution rate was controlled by surface chemical reaction. The activation energy of this process was determined to be 53.91 kJ mol-1.

In this study the dissolution of Colemanite in aqueous acetic acid solutions was investigated in a batch reactor employing the parameters of particle size, solid-to-liquid ratio, and temperature. It was found that the dissolution rate increases with increasing temperature and decreasing solid-to-liquid ratio and particle size. The most effective parameter was particle size with a power of −1.420 after temperature and solid-to-liquid had less effect than the other parameters. The conversion rate increased up to 3.365 M acid concentration and then decreased with increasing acid concentration. No important effect of stirring speed was observed. The activation energy of the process was determined to be 51.490 kJ mol-1. It was determined by graphical and statistical methods that the reaction fits a model in the form of −ln(1 − X) = kt. The following semiempirical mathematical model, which expresses the process well, was established:  −ln(1 − X) = 56 664(D)-1.42(S/L)-0.270 exp(−6193.0/T)t, where X is the conversion fraction, D the particle size, S/L, the solid-to-liquid ratio, and T the reaction temperature.

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In this study, the dissolution of phosphate ore from Mazidagi-Mardin, Turkey, the products formed, and the dissolution kinetics were investigated in S02-saturated water. In experiments, particle size, stirring speed, solid/liquid ratio, and temperature were chosen as parameters. It was determined by X-ray diffractometer that the final solid product contains CaHP0,r2H20, Ca3(S03)2*S04*12H20, and CaS04*2H20. It was observed that the dissolution rate increased with the increase in stirring speed and reaction temperature, and with the decrease in particle size and solid/liquid ratio. A semiempirical mathematical model in the following form, including the effect of the parameters was established to express the dissolution kinetics of phosphate ore: -ln(l -X) = 35.874D-0-612í¿>0•380• (S/L)"°-826e"2575/™•781, where X is the conversion fraction of the ore, w is stirring speed, D is particle size, and S/L is the solid/liquid ratio in weight. The activation energy for the process was found to be 21 408.55 J mol-1.

[20]. In many industrial applications, the stability of graphene oxide dispersions plays a crucial role for the proper solvent preparation. Therefore, many researchers have done the studies to understand the dispersion behavior and to improve the dispersion stability. Konios et al. [21] prepared GO and reduced graphene oxide (rGO) dispersions with the different solvents and they showed that the GO and rGO samples forms a stable dispersion with the deionized-water, ethylene glycol and N-methyl-2-pyrrolidone (NMP). Taha-Tijerina et al. [22] prepared a dispersion with the deionized-water, ethylene glycol, ethanol and mineral oil and they illustrated that the GO samples forms a strong stable dispersion with the deionized-water and ethylene glycol. Graphene oxide-deionized water nano-fluids are more attractive options because of the formation of fairly strong stable dispersions with graphene oxide in the deionized water and the elimination of toxic solvents such as NMP.The quality of the dispersions including "strong stability" can be represented with some criteria such as zeta potential value, thermal and electrical conductivity, pH, and particle size. Therefore, many studies have been done to analyze the GO dispersion properties. The average particle size and zeta potential value [22] [29] were analyzed without using any systematic analyzing such an experimental design approach. It has been determined that oxidants and pH of the

In the present study, aimed at the extraction of copper and the concentration of precious metals in anode slime, the optimum process conditions were sought for the dissolution anode slime from the Sarkuysan Co. in Turkey. The blade number of the mechanical stirrer, reaction temperature, O2 flow rate, stirring speed, acid concentration, solid-to-liquid ratio, reaction period, and roasting temperature were chosen as parameters. Using the Taguchi method, the optimum process conditions, at which 99.67% Cu conversion was reached, were found as follows:  blade number 1, reaction temperature 70 °C, O2 flow rate 1.24 × 10-6 m3·s-1, stirring speed 450 rpm, acid concentration 5.43 wt %, solid-to-liquid ratio 0.125 g/mL, reaction period 3600 s, and roasting temperature 300 °C.

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In this study, the reaction kinetics between metallic silver and nitric acid solutions was investigated by taking into consideration the parameters of temperature, solid-to-liquid ratio, particle size, stirring speed, nitric acid concentration, and addition of sodium nitrite. It was determined that the dissolution rate of the process increased with decreasing particle size, solid-to-liquid ratio, and acid concentration, and increasing reaction temperature and stirring speed. It was found that the amount of sodium nitrite in the solution has no significant effect on the dissolution rate. In the present study, the examination of shrinking core models of fluid−solid systems showed that the dissolution of metallic silver in the range of 7.22−14.44 M nitric acid solutions was controlled by the film diffusion. The following semiempirical model, which represented well the process, was developed by statistical methods:  1 − (1 − X)1/2 (5271.13)(D)-0.548(S/L)-0.3(W)0.851(C)-3.41e-18.81/ RT t, where D is the particle size, C the acid concentration, S/L the solid-to-liquid ratio, T the reaction temperature, W the stirring speed, and t the reaction time. The activation energy of the process was found to be 18.81 kJ mol-1.