Application of surface response method (RSM) to optimize ammonia nitrogen removal from fresh leachate using combination of ultrasound and ultraviolet.

Ammonia nitrogen levels are very high in leachate. This study was conducted to optimize the removal of ammonia nitrogen from fresh landfill leachate using a combination of ultrasound waves and ultraviolet irradiation. A sample of fresh landfill leachate was obtained from a municipal landfill site, located in Shahroud (Semnan, Iran) and its ammonia nitrogen was measured by spectrophotometric method. Ultrasound and ultraviolet irradiation were simultaneously used to remove ammonia nitrogen. Box-Behnken design (BBD) based on response surface method (RSM) was applied to analyze and optimize ammonia nitrogen removal by different variables, including pH, contact time, ultrasound frequency and UV intensity. Based on this method, 29 samples with three replications were tested. The analysis of variance indicated quadratic model was significant for removal of ammonia nitrogen from leachate. According to the model, 99.7% removal efficiency (%) of ammonia nitrogen was obtained in the optimal conditions (pH at 9.7, contact time of 59.1 min, ultrasound frequency of 54 kHz and UV intensity of 40 W). The removal efficiency of ammonia nitrogen was obtained 98.6% from the laboratory experiment in these conditions, which agrees well with the predicted response value.

Concentration and health risk assessment of polycyclic aromatic hydrocarbons in commercial tea and coffee samples marketed in Iran.

The aim of the current study was to evaluate the probabilistic health risk and the concentration of 16 polycyclic aromatic hydrocarbons (PAHs) in commercial tea and coffee samples. For determining the mentioned contaminants in sixty-four samples, a reliable and sensitive technique was validated and developed. The technique is established on magnetic solid-phase extraction and gas chromatography-mass spectrometry analysis (MSPE/GC-MS). The maximum mean of Æ©PAHs in coffee samples was 13.75 ± 2.90 µg kg-1, while the minimum mean Æ©PAHs in tea samples was 4.77 ± 1.01 µg kg-1. The mean concentration of benzo(a)pyrene (BaP) in samples ranged from 0.64 to 2.07 µg kg-1 which was lower than that of standard levels (10 µg kg-1) established by the European Union (EU). The Monte Carlo simulation results showed that the actual target hazard quotient (THQ) for the adult and children was equal to 1.63E-04 and 1.67E-04, respectively; hence, non-carcinogenic health risk for consumers is negligible. The result of actual incremental lifetime cancer risk (ILCR) was lower than the limits of safe risk (1E-4), indicating no notable possibility of cancer risk due to the digestion of tea and coffee for children and adults. Therefore, it can be concluded that the amount of contamination of popular commercial coffee and tea available in the Iranian market with PAHs is often similar to that found in other countries and was lower than the standard of EU. Thus, the processing conditions of these products must be controlled to prevent the formation of PAHs due to the suspicion of carcinogenicity and mutation.

Optimization of electro-kinetic process for remediation of soil contaminated with phenanthrene using response surface methodology.

The objective of this work was to investigate the modification of soil contaminated with phenanthrene (PHE) by electro-kinetic remediation (EKR) process using response surface methodology (RSM). The soil sample was obtained from the subgrades (0-30 cm) of an area close to Shahroud City, Northeast of Iran. The effect of variables such as initial pH, voltage, electrolyte concentration, and reaction time on PHE removal was studied. Based on the results obtained from the central composite design (CCD) experiment, the highest and lowest amount of PHE removal was 97 and 20%, respectively. In this study, the variables A, B, C, AB, AC, and C2 with a p value < 0.05 were significant model terms and the parameter of the lack of fit was not significant (p value = 0.0745). Findings indicated that the "predicted R-squared" of 0.9670 was in reasonable agreement with the "adj R-squared" of 0.9857 and the plot of residual followed a normal distribution and approximately linear. Also, the kinetic rates of the removal PHE by the EKR process best fitted with a first-order kinetic model (R2: 0.926). Results of the investigation of the effective variables showed that in values of pH 3, time of 168 h, voltage of 3 V, and electrolyte concentration of 4 mg/L, the removal efficiency of PHE reached 96.6%. Graphical abstract.

Modeling of chromium (VI) removal from aqueous solution using modified green-Graphene: RSM-CCD approach, optimization, isotherm, and kinetic studies.

BACKGROUND: The aim of this study was to investigate the removal of Cr (VI) using Green-Graphene Nanosheets (GGN) synthesized from rice straw. METHODS: Synthesis of the GGN was optimized using response surface methodology and central composite design (CCD). The effect of two independent variables including KOH-to-raw rice ash (KOH/RRA) ratio and temperature on the specific surface area of the GGN was determined. To have better removal of Cr (VI), GGN was modified using the grafting amine group method. In the Cr (VI) removal process, the effects of four independent variables including initial Cr (VI) concentration, adsorbent dosage, contact time, and initial solution pH were studied. RESULTS: The results of this study showed that the optimum values of the KOH/RRA ratio and temperature for the preparation of GGN were 10.85 and 749.61 °C, respectively. The maximum amount of SSA obtained at optimum conditions for GGN was 551.14 ± 3.83 m 2 /g. The optimum conditions for Cr (VI) removal were 48.35 mg/L, 1.46 g/L, 44.30 min, and 6.87 for Cr (VI) concentration, adsorbent dosage, contact time, and pH, respectively. Based on variance analysis, the adsorbent dose was the most sensitive factor for Cr (VI) removal. Langmuir isotherm (R2 = 0.991) and Pseudo-second-order kinetic models (R2 = 0.999) were the best fit for the study results and the Q max was 138.89 mg/g. CONCLUSIONS: It can be concluded that the predicted conditions from the GGN synthesis model and the optimum conditions from the Cr (VI) removal model both agreed with the experimental findings.

Valorization of biomass into amine- functionalized bio graphene for efficient ciprofloxacin adsorption in water-modeling and optimization study.

A green synthesis approach was conducted to prepare amine-functionalized bio-graphene (AFBG) as an efficient and low cost adsorbent that can be obtained from agricultural wastes. In this study, bio-graphene was successfully used to remove Ciprofloxacin (CIP) from synthetic solutions. The efficacy of adsorbent as a function of operating variables (i.e. pH, time, AFBG dose and CIP concentration) was described by a polynomial model. A optimal99.3% experimental removal was achieved by adjusting the mixing time, AFBG dose, pH and CIP concentration to 58.16, 0.99, 7.47, and 52.9, respectively. Kinetic model revealed that CIP diffusion into the internal layers of AFBG controls the rate of the process. Furthermore, the sorption process was in monolayer with a maximum monolayer capacity of 172.6 mg/g. Adsorption also found to be favored under higher CIP concentrations. The thermodynamic parameters (ΔG°<0, ΔH°>0, and ΔS°>0) demonstrated that the process is endothermic and spontaneous in nature. The regeneration study showed that the AFBG could simply regenerated without significant lost in adsorption capacity.

Hormones removal from municipal wastewater using ultrasound.

Estrogens are one of the micro-pollutants in the wastewater which have detrimental effects on water living organisms. The aim of this study was to evaluate the efficiency of ultrasound to reduce the estrogen (E1) and 17 beta-estradiol (E2) from municipal wastewater. Hence, a cylindrical batch reactor was designed. The effects of powers, frequency, exposure time and pH on reduction efficiency were investigated. The residual concentration of E1 and E2 hormones was measured in reactor effluent by electrochemiluminescence (ECL) method. The results showed that ultrasound removed 85-96% of both E1 and E2 hormones after 45 min while other parameters changes in the range of their operations. Also, the frequency and power of ultrasound had a significant effect on reduction efficiency of hormones while the exposure had no significant effect. Furthermore, the interaction of power and frequency reduced their efficacy to 64.3% (Pvalue = 0.005). The result also indicated that the ultrasound waves have high ability to reduce Steroid hormones from municipal wastewater. The proposed method can be considered as one of the significant strategies for reduction or destruction of hormones from wastewater due to the non-generation of dangerous by-products and the low energy consumption.

Application of a thin film of poly(solochrome black T) as a redox mediator for the electro-catalytic simultaneous determination of dopamine and acetaminophen in the pharmaceutical and biological samples.

Glassy carbon electrode was successfully modified with a thin film of poly(solochrome black T) and applied for the sensitive and selective voltammetric simultaneous determination of dopamine and acetaminophen. The preparation and basic electrochemical behavior of poly(solochrome black T) film on the glassy carbon electrode were investigated in details. The modified electrode with polymeric thin film exhibits excellent electro-catalytic activity toward the oxidation of dopamine and acetaminophen. The anodic peaks of the both species were well defined with lowered oxidation potential and enhanced oxidation peak currents. The modified electrode was used as a voltammetric sensor for sensitive simultaneous determination of dopamine and acetaminophen free from ascorbic acid and uric acid interferences. Under the optimum conditions, the detection limits were 0.092 and 0.142 µmol L(-1) for DA and AP, respectively. The proposed sensor has been successfully used in analysis of pharmaceutical and biological samples.

Design and implementation of integrated solid wastes management pattern in industrial zones, case study of Shahroud, Iran.

BACKGROUND: The aim of the study was to design and implementation of integrated solid wastes management pattern in Shahroud industrial zone, evaluates the results and determine possible performance problems. This cross - sectional study was carried out for 4 years in Shahroud industrial zone and the implementation process included:1- Qualitative and quantitative analysis of all solid waste generated in the city, 2- determine the current state of solid waste management in the zone and to identify programs conducted, 3- Design and implementation of integrated solid wastes management pattern including design and implementation of training programs, laws, penalties and incentives and explain and implement programs for all factories and 4- The monitoring of the implementation process and determine the results. RESULTS: Annually, 1,728 tons of solid wastes generated in the town including 1603 tons of industrial wastes and 125 tons of municipal wastes. By implementing this pattern, the two separated systems of collection and recycling of domestic and industrial wastes was launched in this zone. Also consistent with the goals, the amount of solid wastes generated and disposed in 2009 was 51.5 and 28.6 kg per 100 million Rials production, respectively. CONCLUSION: Results showed that implementation of pattern of separated collection, training programs, capacity building, providing technical services, completing chain of industries and strengthening the cooperation between industrial estate management and industrial units could greatly reduce the waste management problems.