optimization

The increase in greenhouse gas levels and the gradual warming of the earth have garnered worldwide interest. The enzyme formate-dehydrogenase can reduce CO2 by converting it into formate, which is subsequently converted into methanol by the enzyme alcohol dehydrogenase. The purpose of this research was to evaluate the effect of different concentrations of IPGT, modifier, induction time and culture medium on the expression of formate-dehydrogenase enzyme and optimization.

Specific primers were designed to amplify the gene fragment using polymerase chain reaction (PCR). The Formate-dehydrogenase enzyme gene was inserted into the pET28b vector, and the recombinant plasmid was used to transform E.coli.  To enhance protein expression, a Taguchi experimental design was conducted to investigate the effects of temperature, inducer concentration, and type of culture medium type on protein expression levels at two different levels.

PCR results confirmed the amplification of formate-dehydrogenase enzyme gene in E. coli DH5α. Induction time and concentration negatively impacted on expression. The highest level of expression of the recombinant protein was observed 24 hours post-induction at a temperature of 25°C, with an IPTG concentration of 0.1 mM in the presence of sorbitol. LB culture medium was chosen as the best expression medium.

This study showed that low concentrations of IPTG were sufficient for producing the recombinant protein, proving to be economical. Reducing the induction time also increased protein expression. LB medium enhanced with sorbitol was identified to be the best culture medium for inducing the expression of the formate dehydrogenase enzyme.

Recent years have witnessed a growing interest in utilizing biocompatible and renewable polymers as efficient adsorbents for removing heavy metals from aqueous solutionsz. This study investigates the efficacy of carboxymethyl cellulose (CMC) hydrogel crosslinked with ferric chloride as a low-cost and effective adsorbent for nickel (Ni) removal from aqueous solutions.

In this research, CMC hydrogel was synthesized through a chemical crosslinking process with ferric chloride. The structural properties of the hydrogel were evaluated using Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). Optimal conditions for Ni removal were determined using Response Surface Methodology (Box-Behnken design) by examining the influence of key variables, including initial Ni concentration, pH, adsorbent dosage, and contact time.

FTIR and SEM analyses revealed that the carboxyl and hydroxyl functional groups present in the hydrogel structure, along with its unique morphology, facilitate Ni adsorption from aqueous solutions through potential mechanisms such as chelation, electrostatic interactions, and the formation of coordination bonds. The highest Ni removal efficiency (87.88%) was achieved under conditions with an initial concentration of 80 ppm, pH of 7.5, adsorbent dosage of 1.5 g/L, and contact time of 30 minutes. The study of variable effects demonstrated that increasing pH enhances Ni removal, while adsorbent dosage and contact time exhibit a lesser impact on removal efficiency. Additionally, results indicated that the reduced second-order statistical model (Box-Behnken) effectively describes the experimental data, and the predicted values align well with observed values.

The findings of this study highlight the high efficiency of CMC hydrogel as an effective polymeric adsorbent for removing Ni ions from moderately polluted aqueous solutions. Furthermore, the results clearly indicate that Ni removal by this adsorbent is significantly influenced by the initial Ni concentration and solution pH. However, the effects of contact time and adsorbent dosage were not significant in the subsequent stages of the process. For future studies, it is recommended to modify the CMC structure through advanced crosslinking methods and combine it with minerals to increase specific surface area, surface charge, and ultimately enhance performance and adsorption capacity.

Cosmetic and personal care industry wastewater contains chemicals and non-biodegradable organic compounds that must be treated before discharge into the environment. This study aimed to compare the efficiency of conventional chemical coagulation and electrocoagulation-flotation processes in treating wastewater from the cosmetic industry.

In this experimental study, both processes were designed using a central composite design (CCD) approach. For the chemical coagulation process, the variables optimized included pH (5-9), rapid mixing time (30-60 sec), slow mixing time (10-20 min), settling time (30-60 min), and the dose of the coagulant (0.5-1 g/L). For the electrocoagulation process, the optimized variables were pH (5-9), direct current intensity (2-4 A), reaction time (40-80 min), the number of electrodes (4-8 n), and the distance between electrodes (2-4 cm).

In both processes, the designed model followed a quadratic model with a high correlation coefficient. The efficiency of the electrocoagulation process in reducing COD levels in cosmetic industry wastewater was significantly higher than the conventional chemical coagulation process. Under optimal conditions, the COD concentration decreased from 570 mg/L to 57 mg/L in the electrocoagulation process. In contrast, the conventional chemical coagulation process achieved 65% efficiency under optimal conditions, reducing COD levels to 199.8 mg/L.

The results indicated that after treatment using the aforementioned processes, the effluent can be safely discharged into the environment

In recent decades, the issue of crop product safety has led to develop methods for analyzing pollutants in crops. In the present study, ultra-trace amounts of lead (II) ions were measured in lettuce and water samples collected from Shahmirzad, located in Semnan province, an area known for its lead-containing mineral mines.

After sampling and pre-preparation, the lead content in each sample was extracted using solid phase extraction with modified silica gel. The recovery percentage of lead was then determined using atomic absorption spectroscopy.

Optimization of key parameters such as pH, adsorbent amount, analyte flow rate, and volume resulted in a recovery rate of 104%. The experiments also demonstrated a very low limit of detection (LOD) of 1.14 ng/mL, a concentration factor of 250, high analyte selectivity of the adsorbent in the presence of interfering ions, and a high adsorbent capacity of 2.93 μg/g.

The evaluation of experimental data indicates that the current study provides a highly selective method that can be applied to the extraction and recovery of various analytes from different sample types.

Today, waste management is one of the important pillars of resource management in hospitals. The purpose of this study was to identify the effective factors in the management of special medical wastes at the source of their production, to analyze these factors, and to determine the most effective ones to improve the quality of management of such wastes.

In this research, the basics and dynamic components of systems were used to investigate the performance of hospital waste management in this field. For this purpose, the main indicators of the organization's performance were extracted from the research literature. Then, using the concepts of system dynamics, the effect of these factors was shown in the form of cause and effect diagrams. To explain the function of the proposed model, research variables were examined in the form of different scenarios to determine the effectiveness of each in different conditions.

According to the presented flow diagram and the proposed scenarios, it was found that by using the optimal scenario, the various variables of the research, such as decontamination rate, collection, and unauthorized entry into urban waste reservoirs, through the explained relationships of the model in it improves about 15 to 40 percent.

The results obtained in this research ultimately lead to the reduction of environmental risks as well as the reduction of hazardous waste production, which can be a basis for explaining waste management strategies in medical centers.

Microperforated panels (MPPs), often considered as potential replacements for fiber absorbers, have a significant limitation in their absorption bandwidth, particularly around the natural frequency. This study aims to address this challenge by focusing on the optimization and modeling of sound absorption in a manufactured MPP.

The study employed Response Surface Methodology (RSM) with a Central Composite Design (CCD) approach using Design Expert software to determine the average normal absorption coefficient within the frequency range of 125 to 2500 Hz. Numerical simulations using the Finite Element Method (FEM) were conducted to validate the RSM findings. An MPP absorber was then designed, manufactured, and evaluated for its normal absorption coefficient using an impedance tube. Additionally, a theoretical Equivalent Circuit Model (ECM) was utilized to predict the normal absorption coefficient for the manufactured MPP.

The optimization process revealed that setting the hole diameter to 0.3 mm, the percentage of perforation to 2.5%, and the air cavity depth behind the panel to 25 mm resulted in maximum absorption within the specified frequency range. Under these optimized conditions, the average absorption coefficient closely aligned with the predictions generated by RSM across numerical, theoretical, and laboratory assessments, demonstrating a 13.8% improvement compared to non-optimized MPPs.

This study demonstrates the effectiveness of using RSM to optimize the parameters affecting MPP performance. The substantial correlation between the FEM numerical model, ECM theory model, and impedance tube results positions these models as both cost-effective and reliable alternatives to conventional laboratory methods. The consistency of these models with the experimental outcomes validates their potential for practical applications.

Ulva rigida is a type of green algae, belonging to the chlorophyta; which is known as a source of carotenoid pigments and chlorophyll due to its numerous chemical compounds. In this research, the extraction of carotenoid pigment was optimized using ultrasound-assisted method by response surface methodology.

green algae Ulva rigida; In May 2022, fresh from the north of Qeshm Island, Direstan coast (Deirestan Gulf), the boundary of the region; The long slope up to Nakhzah and Salakh harbors, with latitude 260732329 and longitude 550848291, was taken. in order to; Optimizing the conditions of carotenoid extraction, using the response surface methodology, with three independent variables; ultrasonic power (5-300 W), ultrasonic time (1.59-18.40 minutes) and biomass-to-solvent ratio (1.63-8.46%).

Optimizing carotenoid extraction conditions using ultrasound-assisted method showed that All independent variables had a significant effect on the efficiency of carotenoids extraction (p<0.05). In the optimum condition of carotenoid extraction using ultrasound-assisted method (ratio of biomass to solvent is 5.57%; ultrasonic power 177.38 W and ultrasonic time 9.93 min), carotenoid content and extraction efficiency were 0.99 ± 0.08 µg/ml and 18.03% respectively.

The content and the extraction efficiency of carotenoid using ultrasound-assisted technology increased 4 times compared to the conventional extraction method. Therefore, using ultrasound-assisted method for extraction of carotenoids from Ulva rigida were considered as an effective process.

 Given the high amounts of metals in the paint sludge, the recovery of metals can be seen as an effective and economic method for reducing its pollution. The combination of mechanochemical process and acid digestion may enhance the recovery yield of metals. In this process, milling parameters play a pivotal role in determining the chemical structure of the final products.

 Paint sludge samples were milled at three speeds of 150, 250, and 350 rpm for 2, 4 and 6 hours. Two weight ratios of ball-to-sample, i.e., 10 and 20 also was worked out. The milled samples were then subjected to acid digestion under the same conditions, and the amount of titanium was measured. The data were analyzed using the Taguchi method with Minitab software. Ethical considerations were taken into account at all stages of the study implementation.

 Among the milling parameters, ball milling speed showed the greatest impact on increasing titanium recovery, with a contribution of 49%, followed by time and ball-to-sample ratio, with contributions of 34% and 17%, respectively. The optimal milling conditions for achieving the highest recovery were determined to be a speed of 350 rpm, a time of 4 hours, and a ball-to-sample ratio of 20.

 Generally, the recovery yield of metals built up by increasing the amount and intensity of milling parameters. However, excessive increases in these parameters may result in the opposite effect and lead to the loss of cost, time, and energy. Therefore, the operating parameters of milling should be optimized, so that the optimal values of speed, time, and the weight ratio of ball-to-sample were obtained here.

The poor degradability of antibiotics in conventional wastewater treatment processes has recently encouraged researchers to use advanced oxidation processes based on persulfate (PS) activation. Therefore, the aim of our study was to remove ceftriaxone through the activation of persulfate with zero valence zinc/ultrasonic waves (Zn0/US).

In this laboratory study, the sample containing the antibiotic ceftriaxone was subjected to persulfate activation through an ultrasonic probe with a frequency of 40 kHz. Optimization of operational parameters such as initial pH, catalyst dose, initial ceftriaxone concentration, reaction time and persulfate concentration was done through response surface methodology (RSM). In optimal conditions, synergistic effect, changes in wavelength scanning, mineralization rate and radical scavenger effect were studied. Finally, ceftriaxone concentration, chemical oxygen demand (COD) and total organic carbon (TOC) were measured through diagnostic devices.

Based on RSM analysis of variance, the maximum removal of antibiotic (94.54%), COD (66%) and TOC (54%) in laboratory conditions including pH equal to 3, 0.75 mg/L persulfate and catalyst concentration, 15 mg/L ceftriaxone and 45 minutes of reaction time were obtained. The presence of tert-butyl alcohol and ethanol as scavengers of hydroxyl and sulfate radicals decreased the efficiency rate of the process to 79% and 45% in the reaction time of 45 minutes and emphasized that the active species participate in ceftriaxone degradation.

Based on the results, the process of Zn0/US/PS can be considered as a pretreatment process for the effective removal of ceftriaxone from water environments.