Evaluation of physical and chemical characteristics of wastewater and sludge of Zahedan urban wastewater treatment plant for reuse.

Following the water shortage in the world, the use of wastewater as a sustainable resource has been considered in large volume. The study conducted to evaluate the physical and chemical characteristics of the wastewater and sludge of the Zahedan urban wastewater treatment plant showed that the wastewater and sludge treatment system of the treatment plant has high efficiency and effectiveness in removing the investigated parameters. The investigated parameters in the effluent included Chemical oxygen demand (COD), Biochemical oxygen demand (BOD), and Total suspended solids (TSS), turbidity, temperature, nitrate, nitrite, phosphate, pH, zinc, cobalt, lead and copper. Also, the investigated parameters in the sludge included Mixed liquor suspended solids (MLSS), Mixed liquor volatile suspended solids (MLVSS), pH, electrical conductivity and heavy metals. The results showed that the average concentration of metals in the treated effluent is Zn > Mn > Cu > Pb > Ni > Cr > Cd ،and Chemical oxygen demand and Biochemical oxygen demand in the effluent of this treatment plant are on average 171 and 44.4 mg/L, respectively, and its discharge in surface water is limited, but it can be applied for agriculture. Also, the purified sludge had the necessary standards and could be used as soil or household fertilizer and compost for agricultural land.

Degradation of reactive red 198 dye from aqueous solutions by combined technology advanced sonofenton with zero valent iron: Characteristics/ effect of parameters/kinetic studies.

Dyes are one of the most common contaminants in industrial effluents, whose continuous release into the environment has become an increasing global concern. In this work, nanoparticles of zero-valent iron (NZVI) were synthesized using the chemical regeneration method ،and were utilized for the first time as a catalyst in the advanced Sono-Nano-Fenton hybrid method for the decomposition of Reactive Red 198 (RR198). The properties of zero-valent iron nanoparticles were analyzed using SEM and XRD. The effect of pH, initial dye concentration, nanoparticle dosage, zero-valent iron and H2O2 concentration on the decomposition efficiency of Red Reactive 198 was investigated. Comparing the efficiency of Reactivate 198 dye degradation in Sonolysis, Sono-NZVI, Sono-H2O2 and Sono-Nano Fenton processes showed that 97 % efficiency was achieved by the Sono-Nano Fenton process in 60 min. The kinetics of the removal process showed that this process follows pseudo-first-order kinetics and the Langmuir-Hinshelwood model. The results indicate that the effectiveness of the ultrasonic process in removing resistant organic pollutants such as dyes increases tremendously with the synergy of the Fenton process.

Magnetic Fe-doped TiO2@Fe3O4 for metronidazole degradation in aqueous solutions: Characteristics and efficacy assessment.

Antibiotics present in aquatic environments can contribute to the emergence of antibiotic-resistant bacterial strains, posing potential threats to public health. Therefore, efficient strategies to remove these compounds from water systems are essential to reduce both ecological and human health risks. This research aimed to assess the photocatalytic removal efficiency of metronidazole (MET) from an aqueous solution using a 15-W bare UVC lamp and magnetic nanocatalysts (Fe-doped TiO2@Fe3O4), which were synthesized using the sol-gel technique. Furthermore, scanning electron microscopy with integrated energy dispersive X-ray analysis (SEM/EDX), X-ray diffractometry (XRD), Differential reflectance spectroscopy (DRS), vibrating sample magnetometer (VSM), and Fourier transform infrared spectroscopy (FTIR) analysis were carried out to characterize the synthesized nanocatalysts. The influence of several factors, such as pH, initial MET, and nanocatalysts concentrations during reaction times of 15-120 min, was studied. The characterization results confirmed that Fe and Ti were successfully integrated into the Fe- doped TiO2@Fe3O4 nanocomposite. Highest MET degradation efficiency (99.37 %) was observed at a pH of 3, with an initial MET concentration of 60 mg/L, nanoparticle dosage of 800 mg/L, and a reaction time of 90 min. The stability of the nanocatalyst was acceptable. The results suggest that OH ions may play a crucial role in the degradation of MET demonstrating photocatalytic degradation can be an effective way to remove MET from water resources. This research sets a precedent for future endeavors aimed at harnessing photocatalysis for environmental remediation of pharmaceutical pollutants.

Health risk assessment of BTEX compounds (benzene, toluene, ethylbenzene and xylene) in different indoor air using Monte Carlo simulation in zahedan city, Iran.

The presence of benzene, toluene, ethylbenzene, and xylene compounds (BTEX) in the breathing air outside and inside buildings is one of the most significant problems related to human health today. This study was performed to determine the concentration of BTEX pollutants in indoor environments. PhoCheck was used to detect the concentration of BTEX compounds. In this study, the concentration (BTEX pollutant) was assessed in four indoor spaces, including restaurants, laundries, hair salons, and photocopying centers. The results showed that the average concentration of all four searched compounds was higher than the recommended limit of the Environmental Protection Agency (EPA). The results of carcinogenic risk assessment by benzene and ethylbenzene compounds show 2153 × 10-4 and 913 × 10-5 respectively. The HQ values for toluene and xylene were 1.397 and 0.505, respectively, indicating that exposure to toluene alone may have adverse effects on human health, while exposure to xylene alone has no adverse effects. The hazard index (HI) for toluene and xylene pollutants was higher than one. An HI value higher than one means that the two contaminants toluene and xylene in the air we breathe may have adverse effects on human health. As a result, the necessary control measures should be taken to prevent the unfavorable effects of these two pollutants.

Evaluation of water quality of Chahnimeh as natural reservoirs from Sistan region in southwestern Iran: a Monte Carlo simulation and Sobol sensitivity assessment.

Maintaining the water quality is essential because of the limitation of drinking water bodies and their significant effects on life. Recently, much scientific interest has been attracted to the ecological condition assessment of water resources. Because of numerous health issues connected to water quality, the present work aimed to define the water quality status of Chahnimeh reservoirs, Sistan and Baluchistan province, Iran via the Iran Water Quality Index (IRWQISC), the National Sanitation Foundation Water Quality Index (NSFWQI), and human risk assessment. This cross-sectional descriptive work was accomplished in 4 seasons in 2020. The samples were gathered from 5 various points of Chahnimeh reservoirs. This study led to the results that the NSFWQI index was between 29.4 to 49.32, which showed "bad" quality, and the IRWQI index was between 19.27 and 39.23, which indicated "bad" and "relatively bad" quality. The best water quality based on both indexes was observed in the spring, and the worst was in the fall and summer. The highest value of HQ related to nitrate in drinking water was 1.60 in the group of children. However, according to the Monte Carlo simulation, HQ95% was estimated as 1.29. The Sobol sensitivity analysis of the first-order effect showed that daily water's daily ingestion rate (IR) was the most sensitive input. In addition, the value of the second-order effect indicated that the interaction effect of concentration-ingestion rate was the most sensitive input parameter for HQ. Therefore, regular monitoring is necessary to ensure water safety for human consumption.

Synthesis of Fe-TiO2@Fe3O4 magnetic nanoparticles as a recyclable sonocatalyst for the degradation of 2, 4-dichlorophenol.

2, 4-Dichlorophenol is a type of chlorophenol that, even at low concentrations, causes adverse effects such as anemia, coma, weakening of the nervous system, and cancer in humans and other organisms. Therefore, the aim of this study was to synthesize the Fe-TiO2@Fe3O4 sonocatalyst and to assess the removal efficiency of 2, 4-dichlorophenol using this sonocatalyst. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), value-stream mapping (VSM), Brunauer Emmett Teller (BET), and diffuse reflectance spectroscopy (DRS) analyses were performed for characterizing the synthesized nanoparticles. The effect of different factors, such as pH (3-9), initial concentration 2, 4-dichlorophenol (20-80 mg/L), and level of nanoparticles (200-600 mg/L) at different time points (15-90 min), was assessed on sonocatalytic removal of 2, 4-dichlorophenol, and then the reaction kinetics, process mechanism, and stability of the synthesized nanoparticles were determined under optimal conditions. The highest removal efficiency of 2, 4-dichlorophenol and constant reaction rate was obtained at pH of 5, the initial concentration of 20 mg/L, and the nanoparticles dose of 400 mg/L under ultrasound with a frequency of 35 kHz following the reaction time of 90 min. The maximum mineralization efficiency (total organic carbon TOC) under optimal conditions was 81%. Analysis of the degradation kinetics indicated that the 2, 4-dichlorophenol degradation can follow a first-order reaction. The stability of the synthesized sonocatalyst decreased by 91% after 5 re-uses. This study confirmed the efficiency of the Fe-TiO2@Fe3O4 sonocatalytic process in the degradation and mineralization of 2, 4-dichlorophenol.

Magnetic NH2-MIL-101(Al)/Chitosan nanocomposite as a novel adsorbent for the removal of azithromycin: modeling and process optimization.

In the present study, the magnetic NH2-MIL-101(Al)/chitosan nanocomposite (MIL/Cs@Fe3O4 NCs) was synthesized and used in the removal of azithromycin (AZT) from an aqueous solution for the first time. The as-synthesized MIL/Cs@Fe3O4 NCs was characterized by SEM, TEM, XRD, FTIR, BET, and VSM techniques. The effect of various key factors in the AZT adsorption process was modeled and optimized using response surface methodology based on central composite design (RSM-CCD). The low value of p-value (1.3101e-06) and RSD (1.873) parameters, along with the coefficient of determination > 0.997 implied that the developed model was well fitted with experimental data. Under the optimized conditions, including pH: 7.992, adsorbent dose: 0.279 g/L, time: 64.256 min and AZT concentration: 10.107 mg/L, removal efficiency and AZT adsorption capacity were obtained as 98.362 ± 3.24% and 238.553 mg/g, respectively. The fitting of data with the Langmuir isotherm (R2: 0.998, X2: 0.011) and Pseudo-second-order kinetics (R2: 0.999, X2: 0.013) showed that the adsorption process is monolayer and chemical in nature. ΔH° > 0, ΔS° > 0, and ∆G° < 0 indicated that AZT removal was spontaneous and endothermic in nature. The effect of Magnesium on AZT adsorption was more complicated than other background ions. Reuse of the adsorbent in 10 consecutive experiments showed that removal efficiency was reduced by about 30.24%. The performance of MIL/Cs@Fe3O4 NCs under real conditions was also tested and promising results were achieved, except in the treatment of AZT from raw wastewater.

Removal of Amoxicillin from Aqueous Media by Fenton-like Sonolysis/H2O2 Process Using Zero-Valent Iron Nanoparticles.

High concentrations of antibiotics have been identified in aqueous media, which has diminished the quality of water resources. These compounds are usually highly toxic and have low biodegradability, and there have been reports about their mutagenic or carcinogenic effects. The aim of this study was to apply zero-valent iron-oxide nanoparticles in the presence of hydrogen peroxide and the sonolysis process for the removal of the amoxicillin antibiotic from aqueous media. In this study, zero-valent iron nanoparticles were prepared by an iron chloride reduction method in the presence of sodium borohydride (NaBH4), and the obtained nanoparticles were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and vibrating-sample magnetometry (VSM). Then, using a Fenton-like process, synthetic wastewater containing 100 to 500 mg/L amoxicillin antibiotic was investigated, and the effects of different parameters, such as the frequency (1 and 2 kHz), contact time (15 to 120 min), the concentration of hydrogen peroxide (0.3%, 0.5%, and 6%), the dose of zero-valent iron nanoparticles (0.05, 0.1, 0.5 g/L), and pH (3, 5, 10) were thoroughly studied. A pH of 3, hydrogen peroxide concentration of 3%, ultrasonic-wave frequency of 130 kHz, zero-valent iron nanoparticles of 0.5 g/L, and contaminant concentration of 100 mg/L were obtained as the optimal conditions of the combined US/H2O2/nZVI process. Under the optimal conditions of the combined process of zero-valent iron nanoparticles and hydrogen peroxide in the presence of ultrasonic waves, a 99.7% removal efficiency of amoxicillin was achieved in 120 min. The results show that the combined US/H2O2/nZVI process could be successfully used to remove environmental contaminants, including antibiotics such as amoxicillin, with a high removal percentage.

Non-carcinogenic risk assessment of exposure to heavy metals in underground water resources in Saraven, Iran: Spatial distribution, monte-carlo simulation, sensitive analysis.

Groundwater aquifers are considered the second most abundant water supply for drinking water all over the world. In Iran, ground waters are commonly employed for drinking water, irrigation, and industrial purposes. Heavy metals (HMs) pose human concerns about the groundwater contamination; these pollutants are recognized to be capable of bio-accumulation, long persistence in the natural environment, and toxic effects. In the present research, the content of HMs: Chromium (Cr), Cadmium (Cd), and Lead (Pb) were detected in 89 water samples collected in 2018 by underground water supplies (active wells) of Saravan city. Hazard Quotient (HQ) and Monte Carlo Simulation approach with 10,000 repetitions were applied to discover the human non-carcinogenic impacts of HMs in four groups of ages (adults, teenagers, children, and infants) of consumers. The concentrations of Cr, Pb, and Cd were in the range of 0.49-20, 0.1 to 58.34, and 0.11-12.8 µg/L, respectively. The mean HQ calculated due to exposure to Pb (0.0018-0.0023), Cr (0.0112-0.0186), and Cd (0.0370-0.0615) were lower than one. The findings of sensitivity analysis revealed that HMs concentration had the most contribution effect on human non-carcinogenic risk analysis in four different exposed populations. This study could assist researchers to perform more comprehensive studies with more samples. Therefore, further research is required for decision-makers to plan proper measurements properly.

Adsorption of 4-Nitrophenol on calcium alginate-multiwall carbon nanotube beads: Modeling, kinetics, equilibriums and reusability studies.

In this study calcium alginate-multiwall carbon nanotube (CA/MWCNTs) was synthesized using (CA) calcium alginate and multiwall carbon nanotube (MWCNTs), and its efficiency in adsorption of 4-Nitrophenol (4-NP) in aqueous solution was studied. The structure and properties of the synthesized adsorbent were investigated using scanning electron microscope (SEM), thermal gravimetric analysis (TGA), Fourier transform infrared (FTIR), and X-ray diffraction (XRD). The experimental design was performed using Box-Behnken design (BBD) in which variables pH, CA/MWCNTs, and temperature were examined. The results of the effect of temperature on the removal efficiency of 4-NP showed that the adsorption efficiency decreases with increasing temperature. The results of nonlinear isotherm and kinetics models showed that Langmuir and pseudo-second-order models were more consistent than other models. The maximum adsorption capacity of 4-NP in this study by CA, MWCNTs, and CA/MWCNTs was 136, 168.4, and 58.8 mg/g, respectively, which indicates that the use of MWCNTs on CA could increase the adsorption capacity. The results of reuse of the synthesized adsorbent at 4-NP removal also showed that after 5 reuse of the adsorbent, the removal of 4-NP using CA/MWCNTs is reduced by about 10%, which shows that the synthesized adsorbent can be used several times to adsorb contaminants without significant reduction in the efficiency.

The practical utility of the synthesis FeNi3@SiO2@TiO2 magnetic nanoparticles as an efficient photocatalyst for the humic acid degradation.

Humic acid (HA) compounds in drinking water and wastewater disinfection processes are viewed as precursors of highly toxic, carcinogenic, and mutagenic disinfection by-product chemicals. In recent times, these compounds have gained considerable attention of scientists for their successful removal from aqueous solutions to permissible limits. To achieve this aim, the present study investigated, for the first time, the photocatalytical performance of the synthesis FeNi3@SiO2@TiO2 nanoparticles for the HA degradation under different environmental conditions. The photocatalytic reactions were performed using ultraviolet (UV) radiation, whose intensity was fixed at 2500 µW/cm2 throughout the experimental study. The characterization study performed, using specific diagnostic techniques, revealed the presence of several good morphological, magnetic, and catalytic specifications of the synthesized nanoparticles. The use of the simplified form of the Langmuir-Hinshelwood equation sufficiently describes the experimental data of the HA kinetic degradation, as it shows a high coefficient of regression values. Furthermore, the complete HA degradation was reached under conditions of pH = 3; initial HA concentration = 10 mg/L; FeNi3@SiO2@TiO2 nanoparticles dosage = 0.01 g/L; and reaction time >30 min. Thus, the results obtained from this research suggested that the catalyst of FeNi3@SiO2@TiO2 nanoparticles was an attractive, novel, and effective agent, which could be used for the degradation of HA in the photocatalytic processes.

Modeling of azo dyes adsorption on magnetic NiFe2O4/RGO nanocomposite using response surface methodology.

BACKGROUND: Azo group dyes are the largest group of synthetics dyes that widely used in industries, especially in textile industry. The presence of these organic compounds in wastewaters and their discharge into environment without efficient treatment may cause adverse effect on human, living and aquatic environment. The purpose of this study was to optimize the adsorption of azo dye of Direct Red 81 (anionic dye) and Basic Blue 41 (cationic dye) from aqueous solution onto magnetic NiFe2O4/RGO nanocomposite. METHODS: In this study the response surface methodology (RSM) based on the central composite design (CCD), was used to optimization and modeling of adsorption process DR81 and BB41 dye on NiFe2O4/RGO. in order to investigating the effect of the operating parameters on the adsorption efficiency DR81 and BB41, four influential factors were chosen that includes of pH (3-9), contact time (5-25 min), adsorbent amount (0.02-0.05 g) and initial dye concentration (40-200 mg/L). A total of 30 experiments were performed for each dye in this study. The concentration of dye in solution was measured by spectrophotometer. The structure of synthesized adsorbent was investigated using Scanning Electron Microscope (SEM), X-ray diffraction (XRD), Fourier transform irradiation (FTIR), transmission electron microscope (TEM) and vibrating sample magnetometer (VSM). RESULTS: Analysis of variance (ANOVA) showed that regression model for both dye adsorption with value of P value <0.001 is significant statistically. The correlation coefficient (R2) for DR81 (R2 = 0.9968) and BB41 (R2 = 0.9948) indicated which there is a good agreement between predicted values and the results of the experiments and the model also well predict the adsorption efficiency. Furthermore, the factors of pH, dye concentration and adsorbent dose, have the greatest effect on adsorption, respectively, while contact time have the lowest effect on adsorption of both dyes. The adsorption behavior of the DR81 and BB41 onto NiFe2O4/RGO was best described by the Langmuir and Freundlich isotherm, respectively. The optimum conditions for maximum removal of DR81 (96.41%) was found to be at pH 3, contact time 19.68 min, adsorbent dose 0.02 g and initial dye concentration 40 mg/L. However, the optimum conditions for maximum removal of BB41 (97.87%) was found to be at pH 9 contact time 18.16 min, adsorbent dose 0.02 g and initial dye concentration 40 mg/L. CONCLUSION: The present study shows that magnetic NiFe2O4/RGO nanocomposite have much potential as a powerful adsorbent for the rapid adsorption of anionic (DR81) and cationic dyes (BB41) from aqueous solution.

Human health risk assessment of trace elements in drinking tap water in Zahedan city, Iran.

Daily intake of elements through the consumption of drinking water, due to its detrimental effects, is accounted for an important concern. Although the health risk assessment of heavy metals in different water sources has extensively carried out in various studies, the effect of age and the concentration of all trace elements in drinking tap water have neglected. Therefore, this study was conducted to evaluate the concentrations of heavy metals, e.g., As, Cd, Cr, Ni, Pb, B, Al, Hg, Mn, Zn, Cu, Fe, Se and Ba in the drinking tap water of Zahedan city and to estimate their non-carcinogenic and carcinogenic effects. Moreover, this is the first research in Iran that has also been dedicated to complete investigation on daily intakes of trace elements in tap water. A total of 155 samples of drinking water were randomly taken from the tap water and were analyzed using ICP-OES device. The estimation of the carcinogenic and non-carcinogenic risks of analyzed elements was carried out based on the guidelines of the U.S EPA. The hazard index (HI) values for children and adult age groups were 9.84E-01 and 4.22E-01, respectively. The cumulative Excess Lifetime Cancer Risk (ELCR) for carcinogenic trace elements was in range of tolerable carcinogenic risk 10-6 to10-4 and for all carcinogenic elements were in the order of Pb > Cd > Cr. It also detected that the total carcinogenic risks of the Cd, As and Cr in water samples through the ingestion route are at the levels of "low risk" and "low-medium risk".

Data on modeling of enzymatic elimination of Direct Red 81 using Response Surface Methodology.

In this article, three variables including laccase dose, 2,2'-Azinobis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS) dose and pH were used to modeling of Direct Red 81 (DR81) elimination from aqueous solutions by laccase-mediated system. Obtained data indicated that the predicted and experimental values were close for DR81 elimination, and the regression was also able to give a good prediction of response for DR81 elimination (R-Squared = 0.9983). From the experimental, the highest elimination of the DR81 was 95. 5% after 30 min incubation at pH 5, temperature 40 °C, ABTS 0.2 mM, and initial concentration of DR81 50 mg L-1 in the presence of 0.2 U mL-1 of the laccase. The data showed that the laccase can be used as a "green" technology for treating of dyes from aqueous solutions. Data analysis was performed using Design-Expert version 7.0.0 (Stat-Ease, trial version).

Direct Blue 71 removal from aqueous solution by laccase-mediated system; A dataset.

The removal of Direct Blue 71 (DB71), by laccase (EC 1.10.3.2, p-bezenediol:dioxygen oxidoreductases) enzyme in presence of 2,2'-Azinobis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS), in aqueous solution was investigated. Data on this article focused on the optimizing and modeling of DB71 removal by Response surface method (RSM) based on Box-Behnken design (BBD), through studying the effective variables as follows: ABTS dose (0.05-0.2 mM), Laccase dose (0.05-0.2 U mL-1), and pH (3-7). The results of experimental showed that laccase was able to removal DB71 with removal percentage of 83% at concentration of 50 mg L-1 after 30 min incubation in presence of ABTS 0.2 mM, at temperature 40 °C and pH 5. The Analysis of Variance (ANOVA) for the predicted quadratic model was done and quadratic equation showed significant R-Squared (0.9969), Adjusted R-Squared (0.9914) and Adequate Precision (49.7). The lack of fit is not significant due to p-value prob > F more than 0.05.

Data on corrosive water in the sources and distribution network of drinking water in north of Iran.

This study aimed to determine the parameters of scaling and corrosion potential of drinking water in sources and distribution networks of water supply in two cities of north of Iran. The results of Amlash water sampels analysis in winter revealed that the average values of Langelier, Ryznar, Aggressive, Pockorius, and Larson- skold indices was -1.31, 9.73, 11.5, 9.74 and 0.24, respectively, but, in summer they were -1.51, 10.71, 11.36, 10.72 and 0.25, respectively. For Rudsar, the results of water sampels analysis in winter illustrated that the average values of Langelier, Ryznar, Aggressive, Pockorius, and Larson was -1.12, 9.69, 11.33, 9.19 and 0.16, respectively, while, in summer they were -1.05, 10.04, 11.92, 10.18 and 0.19, respectively. The beneficial of this data is showing the clear image of drinking water quality and can be useful for preventing the economical and safety problems relating to corrosion and scaling of drinking water.

Comparison of Moringa stenopetala seed extract as a clean coagulant with Alum and Moringa stenopetala-Alum hybrid coagulant to remove direct dye from Textile Wastewater.

In this study, the efficiency of Moringa stenopetala seed extract was compared with alum and M. stenopetala-alum hybrid coagulant to remove Direct Red 23 azo dye from textile wastewater. The effects of parameters such as pH, coagulant dose, type of salt used for the extraction of coagulant and initial dye concentration on dye removal efficiency were investigated. Moreover, the existing functional groups on the structure of M. stenopetala coagulant (MSC) were determined by Fourier transform infrared spectroscopy, and the morphology of sludge produced by MSC, alum, and hybrid coagulant was characterized by scanning electron microscopy. Ninhydrin test was also used to determine the quantity of primary amines in the MSC and Moringa oleifera coagulant (MOC). According to the results, with increasing the coagulant dose and decreasing the initial dye concentration, dye removal efficiency has increased. The maximum dye removal of 98.5, 98.2, and 98.3 % were obtained by using 240, 120, and 80 mg/L MSC, alum and hybrid coagulant at pH 7, respectively. The results also showed MSC was much more effective than MOC for dye removal. The volume of sludge produced by MSC was one fourth and half of those produced by alum and hybrid coagulant, respectively. Based on the results, hybrid coagulant was the most efficient coagulant for direct dye removal from colored wastewater.

Sonocatalytic degradation of humic acid by N-doped TiO2 nano-particle in aqueous solution.

BACKGROUND: Un-doped and N-doped TiO2 nano-particles with different nitrogen contents were successfully synthesized by a simple sol-gel method, and were characterized by X-ray diffraction, field emission scanning electron microscopy, Energy dispersive X-ray analysis and UV-visible diffuse reflectance spectra techniques. Then enhancement of sonocatalytic degradation of humic acid by un-doped and N-doped TiO2 nano-particles in aqueous environment was investigated. The effects of various parameters such as initial concentration of humic acid, N-doping, and the degradation kinetics were investigated. RESULTS: The results of characterization techniques affirmed that the synthesis of un-doped and N-doped TiO2 nano-particles was successful. Degradation of humic acid by using different nano-particles obeyed the first-order kinetic. Among various nano-particles, N-doped TiO2 with molar doping ratio of 6 % and band gap of 2.92 eV, exhibited the highest sonocatalytic degradation with an apparent-first-order rate constant of 1.56 × 10(-2) min(-1). CONCLUSIONS: The high degradation rate was associated with the lower band gap energy and well-formed anatase phase. The addition of nano-catalysts could enhance the degradation efficiency of humic acid as well as N-doped TiO2 with a molar ratio of 6 %N/Ti was found the best nano-catalyst among the investigated catalysts. The sonocatalytic degradation with nitrogen doped semiconductors could be a suitable oxidation process for removal of refractory pollutants such as humic acid from aqueous solution.

Heavy metal contamination in street dusts with various land uses in Zahedan, Iran.

A total of 78 street dust samples (75 within city and 3 from suburban) were collected from different areas with various land use within the city of Zahedan in November 2013 at the end of a long dry period. After digestion, the concentrations of Cd, Cr, Cu, Ni, Pb, and Zn were measured by using ICP-OES. The degree of pollution by heavy metals was assessed with respect to the background concentration by calculation and comparison of the pollution index, integrated pollution index (IPI) and enrichment factor (EF). The mean IPI values (aggregate of six heavy metals) in commercial, high traffic, industrial, urban park, and residential were 3.65, 2.76, 1.68, 1.53 and 1.25, respectively. The results of EF analysis showed almost all sampled urban land use types to be enriched in heavy metals compared with sampled background levels, suggesting heavy metals contamination of street dust in the urban center is from anthropogenic sources.