M. Muhtar Kocakerim

An empirical model for kinetics of boron removal from boron-containing wastewaters by ion exchange in a batch reactor

In this study, it was investigated boron removal from boron containing wastewaters prepared synthetically. The experiments in which Amberlite IRA 743, boron specific resin was used was carried out in a batch reactor. The ratio of resin/boron solution, boron concentration, stirring speed and temperature were selected as experimental parameters. The obtained experimental results showed that percent of boron removal increased with increasing ratio of resin/boron solution and with decreasing boron concentration in the solution. Stirring speed and temperature had not significant effects on the percent of total boron removal, but they increased the starting boron removal rate. As a result, it was seen that about 99 % of boron in the wastewater could be removed at optimum conditions. On the other hand, the process kinetics were predicted by using heterogeneous fluid-solid reaction models. It was seen statistically that the kinetics of this process agreed the pseudo- second order model, as follows: XBl(1−XB) = 11,241.5[OH][C]−1.76[S/L]2.17exp(−19,57l.2/RT)t1.24

Dissolution kinetics of colemanite in SO2 saturated water

Abstract The kinetics of dissolution of colemanite (a borate mineral) in water saturated with SO2 were studied. The effects of particle size, temperature and stirring rate were determined. It was found that the rate of dissolution increases with decreasing particle size and with increasing temperature, but is unaffected by stirring rate. The dissolution rate was chemically controlled. The activation energy and pre-exponential factor were calculated as 53.97 kJ mol−1 and 26.1 km s−1, respectively.

Utilization of borogypsum as set retarder in Portland cement production

Abstract Boron ores are used in the production of various boron compounds such as boric acid, borax and boron oxide. Boric acid is produced by reacting colemanite(2CaO·3B 2 O 3 ·5H 2 O) with sulphuric acid and a large quantity of borogypsum is formed during this production. This waste causes various environmental problems when discharged directly to the environment. Portland cement is the most important material in the building industry. This material is produced by adding about 3–5% gypsum (CaSO 4 ·2H 2 O) to clinker as a set retarder. The aim of this study was to stabilize borogypsum, and to produce cements by adding borogypsum instead of natural gypsum to clinker. Concrete using cement produced with borogypsum was tested to find the mechanical properties and the test values were compared with those of concrete from cement with natural gypsum. Compressive strength of concrete from cement produced with borogypsum was found to be higher than that of natural gypsum. Also, the setting time of cement with borogypsum was longer than that of the Portland cement.

Dissolution kinetics of ulexite in ammonia solutions saturated with CO2

Abstract The dissolution kinetics of ulexite in ammonia solutions saturated with carbon dioxide were investigated. Experiments investigating the following parameters: concentration of ammonia; particle size; stirring speed; solid to liquid ratio; reaction temperature; and carbon dioxide flow rate; showed that ulexite can be dissolved completely in solutions of carbonic acid at atmospheric conditions. It was found that the dissolution rate increased with increasing ammonia concentration, reaction temperature and calcination temperature, and with decreasing particle size and solid to liquid ratio. It was observed that the flow rate of carbon dioxide and stirring speed have almost no effect on the dissolution rate. It was determined that the dissolution rate of ulexite can be described by a first-order pseudo-homogeneous reaction model and an empirical equation for the process was developed: −1 n (1−X)=1.0×10 5 (C A ) 0.22 (d) −0.92 ( S L ) −0.54 exp ( 6600 T −t) where CA is the ammonia concentration, d the initial particle size and ( S L ) the solid to liquid ratio. The activation energy for the process was found to be approximately 55 kJ mol−1.

Dissolution kinetics of chalcopyrite containing pyrite in water saturated with chlorine

Abstract In this work the dissolution kinetics of chalcopyrite in water saturated with chlorine have been investigated using particle size, reaction temperature and gas flow rate as parameters. It has been found that the dissolution rate decreased with an increase in particle size and reaction temperature, but increased with an increase in gas flow rate. The mechanism by which the dissolution proceeds has been deduced. It has been concluded that the dissolution is controlled by diffusion through the product layer. The activation energy was calculated as 9.06 kJ mol −1 .

Recovery of boron of the sieve reject in the production of borax

Abstract Boron ores are one of the most important underground richness of Turkey. Various boron compounds are produced from these ores. The most important one of them is borax. During the borax production process, a large quantity of the boron oxide (B 2 O 3 ) is discharged by the trommel sieve waste (TSW). Also, this waste causes different environmental problems when it discharged directly to the environment. In this study, evaluation of the reactor waste discharged directly to environment during borax production was investigated to recover B 2 O 3 and therefore to reduce the toxic effect of the waste. For this purpose, the TSW was leached by SO 2 -saturated water at various experimental conditions. It was found that the 90% of B 2 O 3 in the waste was recovered. In addition, about 80% of CaO in the waste dissolved in the leaching solution. A part of the dissolved CaO converted to CaSO 3 · 1 2 H 2 O and Ca(HSO 3 ) 2 which can be used in the paper industry and in other some industries.

Kinetic Investigation of Reaction Between Metallic Silver and Nitric Acid Solutions

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, stirring speed, nitric acid concentration, particle size and addition of sodium nitrite. It was determined that the dissolution rate of the process increased with decreasing particle size and solid-to-liquid ratio, and increasing nitric acid concentration, reaction temperature and the amount of the sodium nitrite in the solution. In addition, it was observed that the stirring speed had more effect on the dissolution rate at low stirring speeds than at high stirring speeds. In the present study, the examination of shrinking core models of fluid-solid systems showed that the dissolution of metallic silver in the nitric acid solutions was controlled by the reaction on the surface. A semiempirical model, which represented well the process, was developed by statistical methods. The activation energy of the process was found to be 57.66 kJ mol–1.

Dissolution kinetics of some borate minerals in CO2-saturated water

Abstract Dissolution kinetics of inyoite and inderite, two boron-containing minerals, in water saturated with carbon dioxide were investigated. Particle size, gas flow rate, and temperature were the parameters chosen. A decrease in particle size and an increase in temperature enhanced the dissolution rate, while gas flow rate had no effect on the rate. Dissolution was found to be chemically controlled for both minerals. Activation energies for the dissolution were determined as 58.5 kJ mol −1 for inyoite, and 61.3 kJ mol −1 for inderite.

Dissolution kinetics of calcined colemanite in ammonium chloride solution

Abstract The leaching kinetics of calcined colemanite in ammonium chloride solutions were studied. The effects of calcination temperature, solution concentration, reaction temperature and pre-hydration were evaluated. The rate of dissolution increased with increasing calcination temperature, solution concentration and reaction temperature, while it was not affected by pre-hydration. It was found that the dissolution rate, based on the homogeneous reaction model, can be expressed as: (1 − x) −1 − 1 = k [ NH 4 Cl ] 3 4 t . The activation energy for the dissolution of the colemanite sample calcined at 400°C was found to be 89 kJ mol−1.

Effects of operational parameters on cadmium removal from aqueous solutions by electrochemical coagulation

Abstract The aim of present study is to investigate the feasibility of cadmium removal from water using electrocoagulation. Electrocoagulation (EC) is an electrochemical wastewater treatment technology with increased popularity and considerable technical improvements. In the study, effects of operating parameters such as initial solution pH, initial concentration (C 0), reaction time (t), stirring speed, and conductivity (κ) on cadmium removal from synthetic wastewater-containing cadmium in the batch electrocoagulation process were investigated. It was found from experimental results that initial solution pH is important parameter affecting cadmium removal. pH of initial solution was in the range of 3 to 6 in the experiments. The largest cadmium removal efficiency was obtained with pH 6. pH 6, obtained from initial solution whose pH was 6, reached an agreement with activity to pH diagrams for Al+3 species in equilibrium with Al(OH)3. Although specific energy consumption increased with decreasing cadmium c...