دوماهنامه مهندسی شیمی ایران
پیاپی 120 (فروردین و اردیبهشت 1401)

Highly porous polymers are mainly produced by emulsion polymerization. In this study, first the emulsion synthesis of poly (styrene-divinylbenzene) was performed and then the effect of increasing the amount of salt in the aqueous phase on the structure of porous polymer was investigated. Scanning electron microscopy was used to study the surface morphology and determine the size distribution of surface cavities. The appropriate amount of aqueous phase to oil phase for emulsion polymerization and production of porous polymer is at least 75% and adding of one percent of salt in the aqueous phase caused more pores with smaller size on the surface of the porous polymer and by increasing the salt, pores with larger diameter and more uniform distribution were obtained. According to the purpose of the study, which was to create fine surface cavities, the appropriate sample in this field was a sample containing 1% salt with a ratio of water phase to oil phase of 75% to 25%, in which case more cavities with smaller size in two index sizes with distribution uniform and symmetrical scattering with PDI of about 1 with an average diameter of 5.21 μm was obtained.

In this study, the effect of the electrocoagulation process on the performance of the membrane bioreactor system was investigated using a laboratory setup and synthetic wastewater. First, the reactor without electric current, then in four different modes including anode and cathode (Al), the distance between anode and cathode (3.5, 2.5 cm), electric field (2.5, 1.5 Volts), and continuous or alternating current applications (one min on, 4 min off) were evaluated. Recent research shows that all of these factors affect membrane flow flux, activated sludge properties, and soluble microbial products (SMP) and extracellular polymeric substances (EPS) concentrations. The results showed that for EMBR reactor (voltage 1.5 V, the distance between anode and cathode 2.5 cm and application of intermittent current (one min on, 4 min off), better performance in reducing membrane fouling, reducing SMP and EPS. So that the membrane fouling rate, EPS, and SMP were reduced by 57%, 59%, and 58%, respectively. Also, the COD removal was 75% for the MBR reactor and 99% for the EMBR.

Natural processes and industrial activities can cause chromium to enter water resources. Chromium in water enters food chain and causes diseases like cancer, skin dermatitis, and other health problems. In this work, cellulose adsorbent, Kraft paper, was used to remove chromium (VI) from water. The ash of the cellulose adsorbent was 2%, and its specific surface area was 3.6 m2/g according to the BJH isotherm adsorption branch. Cellulose adsorbent was also characterized by FTIR, SEM, and EDX methods. The effects of pH were investigated in Cr(VI) adsorption and showed that with the increase in pH of the solution, Cr (VI) removal was decreased.The adsorption isotherm was corresponded to the Langmuir model.The kinetic data was in agreement with the pseudo first order model.The thermodynamic studies showed that Cr (VI) adsorption on the cellulose adsorbent was endothermic and spontaneous. The cellulose adsorbent, Kraft paper, in powder and sheet forms can remove Cr (VI) from water solutions. In the operating conditions of pH 2, powdery adsorbent dose 3 g in 50 mL of chromium solution with the concentration of 10 mg/L in 25 °C after 2 h, 99.16% chromium (VI) removal yield was obtained.

Nowdays, chitosan hydrogels are widely used due to their biocompatibility, biodegradability, cheapness, antibacterial and non-toxic properties. Chitosan hydrogels are made of various crosslinkers, which most of them are toxic and hazardous. Due to many applications of the hydrogels in medicine, drug delivery, tissue engineering and food industry, it is better to use safe and non-toxic crosslinkers in order to produce chitosan hydrogels. Vanilla is a natural and non-toxic aldehyde that can be used as a crosslinker. In addition, vanilla enhances the antimicrobial and mechanical properties of chitosan hydrogels. This paper reviews the various properties and applications of the chitosan-vanilla compound, including applications in antimicrobial and anticancer agents, drug delivery, metal ion absorption from water, perfume production and food preservatives and agricultural coatings.

Scaling formation in industrial or domestic installations is an important economic and technical problem. In this study, the percentage of calcium carbonate deposition in the solution based on ASTM D1141 at different LSIs was investigated by using the chemical method. It was revealed that at LSI values greater than 1.8, the probability of CaCO3 deposition is considerably increased. Therefore, at LSI = 2.2 the effect of concentration of different green-scaling inhibitors including homopolymers, copolymers and terpolymers on the CaCO3 deposition process was investigated by chemical analysis method and the optimal concentration of scaling inhibitors was determined. For the inhibitors of polyacrylic acid homopolymer (PAA), poly maleic acid homopolymer (PMA), poly acrylic acid: 2-acrylamido-2- methylpropane sulfonic acid copolymer (AA/AMPS) and poly acrylic acid:2-acrylamido-2-methylpropane sulfonic acid: t-butyl acrylamide terpolymer (AA/AMPS/TBAA), the optimal inhibitory concentration was obtained at 5, 5, 2 and 2 ppm concentration, respectively by the chemical method of bulk analysis.

In recent decades, organic dye chemistry has advanced greatly due to the use of dyes in various fields such as electronic devices, linear and nonlinear optics, printing and duplication, sensors and biomedical applications. In the present study, the synthesis of azo dyes based on naphthols, xanthenes and hydroxy coumarins in the presence of nano-ZrO2-SO3H catalyst was investigated. Avoid harmful solvents for the environment, mild conditions, high speed and short reaction time, simplicity of working up process; high efficiency and purity of the synthesized derivatives and recoverable catalyst utilization were the advantages of the proposed method. The structure of the synthesized compounds was determined by comparing their physical properties with reported and using IR and HNMR spectroscopy data.