BTXs removal with transition metals coated beds, considering the plausible reaction mechanisms

In this study, a natural zeolite (i.e., Clinoptilolite) was used as bed of a lab scale packed tower. The bed was coated with two transition metals nano-scale particles (i.e., Fe0 and Cu2O). Each coated metal to bed ratio was 4.6 wt. and the experiments were conducted in air flow of 1 L minG1 and temperature of 200°C. The results showed up to 83.83 of BTX (benzene, toluene and xylene) removal for Fe0 and respectively 32.0 and 56.98 for Cu2O and combined Fe0-Cu2O coated beds. However, the pollutants mineralization/elimination ratio on the combined metals coated bed, with up to 0.83, was greater than the remains which were 0.58 and 0.37 in order for Fe0 and Cu2O coated beds. © 2015 Asian Network for Scientific Information

Feasibility study of recycling and converting acidic sludge to bitumen in used motor oil refining industries

Background and Aims: Thousand tons of acidic sludge is produced daily as by-product in the used motor oil refining industries. The acidic sludge contains unsaturated compounds which are non-polar and asphaltene. The objective of this study was performance improvement of acidic sludge by using the additives (bentonite, polymer SBS, sodium hydroxide and the lime) so that recovery to bitumen.Materials and Methods: The polymer styrene - butadiene - styrene (SBS) is bitumen modifier as one of the elastomer - thermoplastic with weight percentages (2 to 4 percent), bentonite due to the chemical structure as fillers, stabilizers and agent concentration with weight percentages (1,2,4,6,8,10) and lime and sodium hydroxide were used to decreasing acidity rate of acidic sludge and promoting the role of bentonite stability in bitumen with ratios equal (1 to 5 g) were mixed with acidic sludge of industry (samples 50 g) and their effect on the acidic sludge was investigated.Results: Evaluation of studies indicated that because of increasing acidic sludge softening point, temperature from 25 to 48 oC , decrease weight loss from 3% to 1.25, promoting the penetration degree to 230 mm, Frass breaking point to -7 and penetration index (PI) to the degree standard set (+1), the acidic sludge properties and performance were modified. The measurement of last three parameters was unavailable in primary sludge.Conclusion: Environmental and health hazards of acidic sludge will be decreases by treatment and neutralization. Also obtained products can be used in the building and road construction according to its specific bitumen criteria and characteristics.Key words: Recovery - Acidic sludge - Used motor oi

A novel method for recovery of acidic sludge of used-motor oil reprocessing industries to bitumen using bentonite and SBS

ABSTRACT Acidic sludge is a by-product from used motor oil reprocessing industries, which thousand tons of this sludge are disposed into the environment as a hazardous waste material daily. The acidic sludge contains unsaturated compounds that are polar and asphaltene. The bitumen under certain conditions is produced from mixing of bentonite, polymer styrene – butadiene – styrene (SBS), and acidic sludge. Context and purpose: The objective of this study was the recovery of acidic sludge to bitumen using additives such as bentonite and SBS. Also, the effect of additives with different weight percentages (wt%(on the performance parameters of bitumen was evaluated. At first, spilled oil was separated from the acidic sludge by a centrifugal concentrator. Then, concentrated acidic sludge and additives were mixed in together. Finally, the performance tests were carried out to compare the quality of acidic sludge with the obtained products.The results indicated that performance parameters such as softening point (SP), weight loss, penetration degree, PI, Frass breaking point, and temperature susceptibility (TS) were promoted from 37°C, 1.3%, 230 dmm, -0.07854, -5°C and 0.0451 to 54°C, 1%, 130 dmm, 2.7094, -11°C , 0.02721, respectively. According to the paired sample t-test analysis, a significant difference was found between the bentonite dosage and the improved performance parameters from concentrated acidic sludge and obtained products (pvalue ≤.001). The bentonite and SBS with 2 and 4 wt%, respectively were determined as the suitable additives in the recovery of acidic sludge to bitumen

Escherichia Coli Removal from Water Using Electrophotocatalytic Method

Electrochemical has the suitable method of drinking water disinfection. This method leads to production of hydroxyl radicals which are known powerfull oxidant agent. In recent years, water disinfection using electrophotocatalytic method is spreading. The aim of this experimental applied study is to evaluate the removal of Escherichia Coli, as the microbial contamination indicator of water, from drinking water using electrophotocatalytic method. The contaminated water in an electrophotocatalytic reactor were prepared by adding 102-103 cell of E. coli bacteria to drinking water. The studied variables were pH (6-8), the number of bacterial suspensions (102-103 cells / ml), the UV-A lamps (2-4 W), times (5-40 min), the distances between electrodes (2-3.5 cm), layering of zinc oxide nanoparticles (1-3), and voltages (10-40). The findings showed the correlation between removal of cells and UV-A lamps, voltage, and time of electrolysis. Optimal removal (MPN: 0) was obtained at pH 8, time of electrolysis: 5 minutes, 2 layer of nano ZnO, and voltage of 10 V. This result offers that this method is an efficient method for water disinfection. @JASEMKeywords: Escherichia Coli , Water disinfection, Electrophotocatalytic, UV- AJ. Appl. Sci. Environ. Manage. Sept, 2011, Vol. 15 (3) 439 - 44

Amoxicillin degradation with electro-persulfate combined with H2O2 from aqueous solution using response surface methodology

Background: Discharging wastewaters containing antibiotic into the environment causes some adverse effects on the human health and other organisms. The present study investigated the efficiency of electropersulfate combined with hydrogen peroxide (H2O2) process as a chemical oxidation in amoxicillin (AMX) degradation. Methods: Optimization of the significant operational independent variables was explored for removal of AMX. Central composite design (CCD) was employed as a statistical tool for experimental design. High-performance liquid chromatography (HPLC) was used for measuring AMX concentration. The most effective factors of the electro-persulfate and H2O2 on the removal efficiency of AMX such as initial concentration of AMX, initial pH, PS/H2O2 molar ratio, and the current density were measured. Results: The optimum conditions for electro-persulfate removal efficiency of AMX to reach the degradation efficiency of higher than 95.28 ± 2.64% at reaction time of 60 minutes were obtained at pH = 4.23, AMX concentration = 31.9 mmol/L, current density = 39 mA/cm2, and PS/H2O2 molar ratio = 0.82. AMX degradation was satisfactorily predicted by the quadratic model with high possibility and confidence level of 95%. The quadratic model had high regression coefficients (R2 = 0.9964 and R2 adj = 0.9926), which was totally acceptable. The removal efficiency of AMX reduced from 87.3 ± 6.1 to 25.9 ± 9 as pH increased from 5.5 to 7. Conclusion: According to the results, the electro-persulfate and H2O2 process can be suggested as the most effective, high efficient, and in-situ chemical oxidation for degradation of AMX. Keywords: Amoxicillin, Hydrogen peroxide, Oxidation-reduction, Antibioti

Evaluation of photoionization detector performance for measuring the airborne toluene

Background and aims: In the field of chemical agents at workplaces, traditional measurement method for assessing the volatile organic compounds (VOCs) concentration is using a gas chromatograph generally equipped with a flame ionization detector (GC-FID). However, there are some limitations in working with this equipment including equipment accessibility, necessity of highly trained operators, and the high cost of sample analysis. The aim of this study was to evaluate the performance of photoionization detector (PID) as a substitution for GC-FID in the measurement of toluene as a representative of the VOCs in experimental studies. Methods: This study was carried out by an experimental set up for generating toluene known concentrations at 5, 20, 50, 100, 200, 500 and 1000 ppm with relative humidity 13 ±2. The concentration values were measured with PID as well as the National Institute of Occupational Safety and Health (NIOSH) 1501 reference method and results were compared. Results: The results showed a significant difference between the two methods at concentrations higher than 50 ppm while there was no significant difference at 5 ppm and 20 ppm. The correlation coefficient of the toluene concentrations at 5 to 1000 ppm was 0.999. The correction factor for the PID was 1.05 at the studied concentration range. Conclusion: Although the results presented by PID were different from those extracted from the NIOSH reference method, the response was linear. Thus, in studies of measuring airborne concentrations of toluene using this type of detector; the reading values must be corrected by the calculated correction factor

Photochemical of Polychlorinated biphenyl by the photolysis and solvent

Polychlorinated biphenyls (PCBs) are one group of persistent organic pollutants (POPs) that are of international concern because of global distribution, persistence, and toxicity. Removal of these compounds from the environment remains a very difficult challenge because the compounds are highly hydrophobic and have very low solubility in water. The photochemical reactor was of annular geometry with a cylindrical low-pressure mercury lamp. The whole Lamp was immersed in a reactor thermostat controlling the temperature at 32 ± 2 °C. The Polychlorinated biphenyls (PCBs) were analyzed by GC/ECD. The degradation of PCBs in terms of one, two and three lamp was 91.9%, 92.7% and 93% respectively. The degradation of PCBs in terms of use of 10% and 20% of total volume of solution of H2O2 were 88.8% and 93% respectively. The degradation of PCBs in terms of ratio to ethanol with oil transformer in 1:1, 2:1 and 3:1 was 83.4%, 92.5% and 93% respectively. The experiments show that UVC-photolysis of H2O2 leads to a degradation efficiency of PCBs in the presence of ethanol. @ JASEMJ. Appl. Sci. Environ. Manage. December, 2010, Vol. 14 (4) 107 - 11

Investigation of MPTMS-modified magnetic nanoparticles in the removal of lead and cadmium ions from aqueous solution: equilibrium and kinetic studies

زمینه و اهداف: در سال‌های اخیر، مساله آلودگی محیط‌های آبی با فلزات سنگین بسیار مورد توجه محققان قرار گرفته است. بدین منظور، مطالعه حاضر با هدف کارایی نانوذرات مغناطیسی اکسید آهن اصلاح شده با 3- مرکاپتوپروپیل تری متوکسی سیلان در حذف یون‌های فلزی سرب و کادمیوم را از محیط آبی انجام گرفت. مواد و روش‌ها: در مطالعه حاضر نانوذرات مغناطیسی Fe3O4@SiO2-SH به روش ساده هم‌رسوبی در دمای 80 درجه سلسیوس سنتز شد و سپس ساختار و مورفولوژی آن با استفاده از دستگاه‌های XRD، FT-IR،  SEMو TEM مورد شناسایی قرار گرفت. در نهایت آزمایشات جذب بر روی محلول آبی انجام گرفت. در کلیه مراحل انجام پژوهش، موازین اخلاقی، مراعات گردید.   یافته‌ها: طبق نتایج، نانوذرات Fe3O4@SiO2-SH دارای توزیع یکنواخت با هسته کروی Fe3O4 و پوسته SiO2 می‌باشد که توسط لیگاندهای تیول اصلاح شده است. همچنین اثر پارامترهایی نظیر pH، دوز جاذب و مدت زمان تماس بر درصد حذف یون‌های فلزی مورد بررسی قرار گرفت. نتایج تحقیق نشان داد pH معادل با 5 و 6 به ترتیب برای سرب و کادمیوم، زمان تماس 40 دقیقه و دوز جاذبg/L  0/8 شرایط بهینه مناسب جهت حذف یون‌های فلزی از محلول است. معادلات کینتیک و ایزوترم بر این نکته تاکید داشت که روند جذب دو یون فلزی از مدل کینتیک شبه درجه دوم (0/98<R2) و ایزوترم دمایی لانگمویر (0/98<R2) تبعیت می‌کند. نتیجه‌گیری: با توجه به نتایج حاصل، نانو ذرات سنتز شده Fe3O4@SiO2-SH تحت شرایط بهینه می‌تواند كارايي مناسبي در حذف یون‌های فلزی سرب و کادمیوم از محلول‌های آبی داشته باشد.Background and Aims: Environmental pollution by heavy metals has received much attention in recent years. Therefore, this study aims to remove lead and cadmium ions by using silica-coated magnetic nanoparticles modified with mercaptopropyltrimethoxysilane (MPTMS) from aqueous solutions.Materials and methods: In this study, Fe3O4@SiO2-SH magnetic nanoparticles were synthesized via the simplified co-precipitation method at 80°C. The structure and morphology properties of synthesized nanoparticles were characterized by XRD, FT-IR, SEM and TEM. Finally, the adsorption experiments were performed in aqueous media. All stages of this research were conducted ethically.Results: According to the results, Fe3O4@SiO2-SH nanoparticles have a uniform distribution with a spherical Fe3O4 core and SiO2 shell, modified by thiol functional groups. The efficiency of synthesized adsorbent in the removal of metal ions was also investigated considering parameters such as pH, adsorbent dose and contact time. The optimum conditions for lead and cadmium removal were obtained at pH 5 to 6, contact time 40 min and absorbent dose 0.8 g/L. The kinetic and isotherm studies underlined that the process of adsorption of both metal ions follows the second-order (R2> 0.98) and Langmuir isotherm (R2>0.98) models.Conclusion: Based on the results obtained, synthesized Fe3O4@SiO2-SH magnetic nanoparticles can present proper efficiency in the removal of lead and cadmium ions from aqueous media under optimum conditions

Catalytic potential of CuFe2O4/GO for activation of peroxymonosulfate in metronidazole degradation: study of mechanisms

Application of magnetite nanoparticles (CuFe2O4/GO) were anchored on graphene oxide (GO), as a Heterogeneous nanocomposite for activating of peroxymonosulfate (PMS) into Metronidazole (MNZ) destruction. The effect of solution pH, reaction time, effectiveness of water matrix components and trapping factors, different catalyst concentrations, PMS and contaminants were evaluated as operating factors on the efficiency of MNZ degradation. Also, mineralization, stability, reactivity and Recycling tests of the catalyst, and the degradation kinetics were performed. MNZ degradation and mineralization were obtained under optimal conditions (0.2 g/L catalyst, pH = 5, 30 mg/L MNZ and 2 mM PMS), 100 and 41.02, respectively over 120 min. Leaching of Fe and Cu was found <0.2 mg/L for CuFe2O4/GO showed a high stability of catalyst, and a significant recyclability was achieved CuFe2O4/GO within 5 times consecutive use. MNZ degradation affected by anions was reduced as follows: HCO3� > NO3� > Cl� > SO42�. The experimental data were very good agreement with pseudo-first-order kinetic model, and during quenching tests SO4�- radicals played a dominant role in the degradation process of MNZ. As a result, the CuFe2O4/GO/PMS system can be described as a promising activation of PMS in MNZ degradation, due to its high stability, reusability and good catalyst reactivity, and the production of reactive species simultaneously. © 2020, Springer Nature Switzerland AG

Mercury level in biological samples of dentists in Iran: a systematic review and meta-analysis

Exposure to mercury is an important risk to dentists health. The aim of the present study was to assess the pooled mean mercury level (MML) in the urine, blood, nail, and hair of Iranian dentists (IDs) through the meta-analysis technique. Comprehensive and systematic searches were performed in main local databases including SID, Magiran, Iran medex, and ISC as well as internationally available databases including Embase, PubMed and Scopus for all the relevant studies up to 2018. In order to prevent bias in this study and identify eligible studies, various steps of the study was performed independently by two researchers. Out of 13 studies in the meta-analysis process which included 1499 IDs, the mean of the mercury level in the urine, nail, and blood was estimated to be 6.29 (95 CI: 2.61�9.97, I-square: 62.7, P: 0.006), 3.54 (95 CI: 2.81�4.28, I-square: 0.0, P: 0.968), 11.20 (95 CI: 2.28�20.13, I-square: 59.9, P: 0.082), respectively. The mean mercury level (MML) in the biological samples of IDs was higher than the standard of World Health Organization (WHO). So, in accordance with Article 10 of the European Union Regulations (EUR), in the context of the Minamata Convention (MC) on Dental Amalgam (DA), in order to avoid the dangers of mercury exposure in dentists, it is necessary for Iran and other countries to approve laws and to implement a national plan to reduce mercury levels and replace the appropriate materials. © 2020, Springer Nature Switzerland AG