Iranian journal of chemical engineering
Volume:17 Issue: 4, Autumn 2020

In an Iranian zinc smelter plant, nickel and cadmium are removed from the electrolyte solution at the cold purification stage with help of zinc powder. This study tries to investigate the optimal conditions for the removal of these impurities by examining the interactions of effective parameters on the process by the response surface methodology. The results of the experiments showed that cadmium was cemented much more convenient than nickel by the zinc powder. The interplay of parameters showed that increasing the concentration of zinc powder can reduce the time and temperature of the complete reaction. It also neutralized the effect of pH change and mixing speed. The optimum conditions for simultaneous removal of nickel and cadmium were obtained at 75 °C, pH of 4.5, residence time of 45 min, mixing speed of 500 rpm, and 2 g/l zinc powder. Under optimal conditions, more than 99% of nickel and cadmium were removed from the electrolyte solution.

General Purpose Polystyrene (GPPS) has weak properties and this weakness made the applications of this polymer to be limited. Therefore, the use of mixtures of polymers can improve these properties. Different parameters like mixing speed can affect the quality of the properties of the preparing polymer from mixture of several polymers. In this research, the polymer blend of GPPS and Acrylonitril-Butadiene Styrene (ABS) has been investigated. In order to prepare this polymer mixture, GPPS has been assigned as main phase (base polymer) and ABS has been assigned as scattered phase (additive). Firstly, the blended polymer with different weight percentages (0, 0.04, 0.08 and 0.12) of ABS/GPPS in different mixing speed (30, 40, 50 and 60 rpm) has been prepared and for each mixture, Melt Flow Index (C), Vicat Softening Temperature, Tensile at Break and impact test has been measured. The laboratory data collected from different tests, has been simulated by Multi-Layer Perceptron (MLP) method of Artificial Neural Networks (ANN) and the results of the simulated data covered the laboratory data perfectly. The results declare data the presence of ABS in mixed polymer improved the Tensile strength and thermal properties. In order to reach the highest quality in accomplished tests, it is considered to use ABS in high percentage (0.12) and the maximum possible mixing speed (60rpm).

In this study, the inactivation performance of units against pathogenic and biotoxin threats in a water treatment plant are studied. The assessment of assets and hazards of water treatment plant against each of threats are studied by the RAMCAP risk analysis. The experiments showed that the Aflatoxin was eliminated only by disinfection units. The reverse osmosis unit had high efficiency in removing Ricin, while the sand filtration had the lowest efficiency in removing biotoxins. The microbial analysis showed the total coliform bacteria, thermotolerant coliform and HPC index were increased slightly by increasing the incoming water's pH and turbidity, while their count were significantly reduced by increasing the free residual chlorine. Water temperature changes also had a minor effect on microbial indexes. The RAMCAP analysis is used to reduce the vulnerability of units against conventional threats by determining the risk values of the units and finally, the presence of practical solutions.

This research aims to evaluate the effects of dopamine as a link in the hydrophobicity of carbonyl iron particles with stearic acid. In this connection, the effect of stearic acid and oleic acid on the hydrophobicity of carbonyl iron was also investigated. For this purpose, the FESEM analysis was used to observe the surface modification of the particles, and the surface structure of the particle was studied. Also, the magnetic properties of hydrophobic particles were measured by VSM and Magnetic saturation of CI, CI @ Stearic acid and CI @ Dopamine @ Stearic Acid is 200, 169, 131 emu/g respectively,  in which this decrease is not significant. Finally, the contact angles of samples were measured. Basing on the result, the static contact angle of a water drop placed on a bed of the CI @ Oleic acid, CI @ Stearic acid, and CI @ Dopamine @ Stearic Acid were found to be 156.2°, 162.9°, and 169.022° respectively. The result showed that dopamine has a good effect as a link to the hydrophobicity of particles.

Many communities in the world use groundwater as a source of potable water. High nitrate concentration is a serious problem in groundwater usage. This study utilizes a biological denitrification method to investigate a moving bed biofilm reactor (MBBR) for the case of Tehran's groundwater. One pilot-scale MBBR was designed and used in this research with 3-liter volume. The denitrification reactor operates under anoxic conditions. Methanol was used as a carbon source in the reactor throughout the study, and fifty percent of the reactor volume was occupied with KMT packing (k1). To determine the optimum nitrate loading rate, the concentration of nitrate changed from 100 to 400 mg N/l. It was concluded that heterotrophic denitrifying bacteria converted nitrate to nitrogen. According to obtained results, the removal efficiency and optimum loading rate were estimated during the experiments in different concentrations and different HRTs for this type of reactor. Sodium nitrate was in the feed source in the anoxic reactor. The maximum nitrate removal rate was measured to be 2.8 g NO3-N m-2 carrier d-1. Therefore, it was shown that the optimum nitrate loading rate and the optimum COD/N were equal to 3.2 g NO3-N m-2 carrier d-1 and 6 g COD/g N, respectively.

In this work, phosphate bonded refractory was developed using magnesium potassium phosphate cement and its physical, mechanical and thermal properties were evaluated. Cement was prepared from caustic calcined magnesium oxide with addition of mono potassium phosphate. Characterisation of cement was done by XRD and SEM to examine the change in phase and morphology which occurs after hydration of magnesium potassium phosphate cement which is in the form of struvite phase. To evaluate the physical, mechanical and thermal properties, refractory samples were casted and subsequently dried and fired at temperatures range of 1300°C to 1500°C. Then the bulk density, apparent porosity and crushing strength were analysed. It was found that the properties of chemical bonded refractory are better than convectional calcium alumina cement bonded refractory.The refractory specimens sintered at 1400oC, were analyzed for thermal and mechanical properties. They exhibited better wear resistance at both room temperature and at high temperature (1000oC). Properties of calcium alumina bonded refractory were also studied and compared with those made from magnesium potassium phosphate bonding. It is observed that the developed refractories are better in terms of wear resistance and thermal expansion. This indicates that the developed magnesium potassium phosphate bonding can be a good approach for fabricating refractories where high temperature resistance and wear resistance are required.