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Dye is one of the most important environmental pollutants which threats human and environmental health. Due to the solubility and high stability of dye in water, incremental attention has been paid to their destruction and removal from industrial effluents. In this study, the efficacy of ZnO nanoparticles coated on natural zeolite (Zeo) as photocatalyst was evaluated to destroy the safranin dye in water solution under UV light. In order to determine the optimal conditions, the effect of dye concentration and solution pH were investigated. Field-emission scanning electron microscopy images show that ZnO is well situated on the Zeo surface and Fourier-transform infrared spectroscopy analysis confirmed the presence of Fe-ZSM5 Zeo and ZnO anatase phase in the synthesized photocatalyst. Optimal values of pH and the dye concentration for dye removal by synthesized UV/ ZnO-Zeo photocatalyst were 9 and 100 mg/L, respectively. The maximum safranin dye removal (100%) in optimal conditions under UV light was obtained after 105 min. Also, the maximum adsorption capacity ZnO-Zeo catalyst for safranin was 26.35 mg/g. The removal efficiency reduced from 93% at run first to 32.15% at run fifth. In general, the results showed that the UV/ZnO-Zeo process can be used as an effective and efficient method in removing the safranin from aqueous environments.

In the present study, the ability of Pseudomonas putidabiomass on biosorption of Reactive blue 19 (RB19) and tetracycline (TC) antibiotic from aqueous solutions was investigated. Both of these pollutants are harmful to human and environment safety. RB19 and TC are very resistant against the chemical process used currently in the textile industry. And also, the TC is one of the emerging antibiotics that is shown high resistant to the human-harm pathogens in the environment. These work was conducted as a batch system with variable parameters including concentration of pollutants, contact times, biomass dosages, pH, temperatures, and ionic presence. Characterization of the biosorbent was determined by scanning electron microscopy and Fourier-transform infrared spectroscopy. According to the experimental results the optimal removal efficiency obtained at pH 7, the initial concentration of pollutants 50 mg/L, the contact time 24 h, the temperature 37°C, and the sorbent dosages 0.1 g/L for TC and 1 g/L for RB19. However, the removal efficiencies for RB19 and TC increased from 62.94 to 80.25 for RB19 and from 30.69 to 54.97 for TC with increasing the biosorbent amounts. For TC, the biosorption capacity and the removal efficiency improved with increase in the TC concentration. Moreover, increasing the initial dye concentration led to enhancing biosorption capacity while the removal efficiency reduced. The highest efficiency obtained at pH 7 and 6–7 for TC and RB19, respectively. Additionally, isothermal analysis of the biosorption process agreed with the Langmuir model under (R2= 0.8919). The maximum biosorption capacity (qmax) for TC and RB19 were 19.84 and 5.94 mg/g, respectively. According to the results obtained, P. putidastrain has a promising biosorption capacity and can be used as a native strain for bio-synergy of activated sludge in the removal of TC and RB19 compounds from aqueous solutions.

These dyes have the potential for mutagenicity, carcinogenicity, and unwanted color on the one hand, and on the other hand, cause the production of toxic by-products in aqueous media. The aim of the present work is to synthesize scallop shell/iron oxide(II) nanocomposite and evaluate its efficiency in removing Direct red 81 (DR81) dye from aqueous solutions. Iron oxide nanoparticles were prepared by co-precipitation method and then the scallop was coated with iron oxide. The properties of synthesized nanocomposite were identified using Fourier-transform infrared spectroscopy, field-emission scanning electron microscopy, and X-ray diffraction. Effect of dye concentration (20–120 mg/L), contact time (0–240 min), adsorbent dosage (0.5–2.5 g), pH (3–11), and temperature (25°C–55°C) was investigated on decolorization efficiency of the process. Under optimal conditions (an initial DR81 concentration of 25 mg/L, pH of 3, adsorbent dose of 0.5 g, and contact time of 90), more than 98% of the dye was removed. The results showed that the efficiency decreases with increasing concentration. Moreover, by increasing the contact time and adsorbent dosage, dye adsorption percentage was enhanced. The maximum adsorption coefficient was 46.4 mg/g. In addition, Freundlich and Langmuir models were used to analyze the experimental isotherm data. The kinetic data of the adsorption process were in good agreement with the pseudo-second- order kinetic model (0.995). The experimental data of the adsorption process followed the Langmuir model (R2= 0.91). The results show that Fe2O3nanoparticles coated with scallop shell as an environmentally friendly adsorbent can be effective in the adsorption of DR81.

Disinfection is one of the most important stages of water and wastewater treatment. Today, the use of photocatalytic processes by sunlight as a sustainable way of water disinfection has been noted. The purpose of this study was to remove coliform and fecal coliform from the effluent of a hospital sewage treatment plant using the solar/N-doped titanium dioxide (TiO2) process. In order to conduct the experiments, the raw samples (effluent of secondary sedimentation) were taken from the Ali Ibn Abi Talib hospital wastewater treatment plant in Zahedan City, Iran. N-doped TiO2nanoparticles and the samples were poured into the reactor and then exposed to direct sunlight in summer. The results indicated that the photocatalytic process efficiency was enhanced by increasing reaction time and nanoparticles dosage. Furthermore, it was found that N-doped TiO2nanoparticles and sunlight had a synergistic effect on the deactivation of coliform and fecal coliform. The number of coliforms and fecal coliforms bacteria cells decreased from 5 × 105to 7 × 103MPN/100 mL and 4 × 103to 2 × 102MPN/100 mL in the solar/N-doped TiO2process after 150 min, respectively. It has been generally concluded that the solar/N-doped TiO2process can effectively deactivate a wide range of real effluent microorganisms on a laboratory scale.

In this research, multi-walled carbon nanotubes-CoFe2O4magnetic (MWCNTs-CoFe2O4) based-magnetic nanocomposite was used for removal of Remazol Brilliant Blue Reactive (RBBR) dye, which is one of the most widely used organic dyes in the textile industry. The various characterization methods such as Fourier-transform infrared spectroscopy, field-emission scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, transmission electron microscopy, Brunauer–Emmett–Teller and vibrating sample magnetometer were used to confirm the formation of nanocomposite adsorbent and study its magnetic properties. The effective parameters on the removal process were time, adsorbent dose, dye concentration, pH and temperature. The optimal values of each of these parameters were determined as 40 min, 0.4 g, 20 mg/L, 3 and 298 K, respectively. The removal efficiency of RBBR dye in the presence of MWCNTs-CoFe2O4nanocomposite was 95% under optimal conditions. The maximum adsorption capacity (qmax) of MWCNTs-CoFe2O4for RBBR dye was 106.5 mg/g. The obtained experimental data were then analyzed with different isotherms such as Langmuir, Freundlich and Temkin and the results showed a very good agreement of the data with the Langmuir isotherm (R2= 0.9998). In addition, two quasi-first-order and quasi-second-order kinetic models studied the kinetic of the adsorption process. It was observed that the process follows the quasi-second-order kinetic. Finally, a thermodynamic study was carried out at four temperatures of 298, 308, 318 and 328 K to calculate the Gibbs free energy (ΔG) changes, enthalpy changes (ΔH) as well as entropy changes (ΔS). The calculated values for the mentioned thermodynamic parameters were –8.93 kJ/mol, –32.38 kJ/mol and 0.078 kJ/mol K, respectively. The results showed that dye adsorption is an exothermic, spontaneous process and is associated to a reduction in system irregularities.

In this study, the potential of natural coagulants such as plant extracts of Cichorium intybus(Ci), Cichorium pumilum(Cp), and Cichorium endivia(Ce) was investigated for removal of water turbidity. For conducting this study, distilled water and salts of KNO3, NaNO3, NaCl, and KCl were used to prepare the extracts, and parameters such as the turbidity removal percentage, the optimal concentration of plant extracts, the type of extracted extracts, pH, the amount of total dissolved solids, hardness, alkalinity, chloride, and sulfate were examined before and after the coagulation process. In this study, after determining the efficiency of different coagulants in removing turbidity from turbid water, the performance of the extracts was compared with the conventional chemical coagulant of aluminum sulfate (alum). The highest turbidity removal efficiency among different extracts was related to the use of Cichorium intybusextract; the high levels of protein and amine in this extract were proved by ninhydrin and Fourier-transform infrared spectroscopy tests. After determining the best plant extract (Cichorium intybusspecies extract), the hybrid coagulant was prepared using Cichorium intybusplant extract and alum (Ci/alum) in ratios of 1:1, 1:2, and 2:1, and its potential was also studied. The results showed that increasing the coagulant concentration to an optimal level is associated with an enhancement in turbidity removal efficiency. However, increasing the coagulant concentration to levels higher than the optimum value does not affect turbidity removal efficiency, and the removal efficiency remains almost constant. The maximum turbidity removal efficiencies using Ci, alum, and hybrid Ci/alum (1:1 ratio) were 92%, 90%, and 98%, respectively, which indicates the higher efficiency hybrid coagulant in the removal of turbidity from aqueous media. The results also showed that the use of 1 M NaCl solvent for the extraction of coagulants is more effective compared to other solvents used in this study.

In this study, the photocatalytic degradation of 2,4,6-trichlorophenol (2,4,6-TCP) was evaluated under UV radiation by Fe-doped titanium dioxide (Fe-doped TiO2) nanoparticles (NPs) which were synthesized by a sol-gel method. Diffuse reflectance spectroscopy (DRS), X-ray diffraction (XRD), and scanning electron microscopy (SEM) were applied to identify the synthesized nanoparticles. According to the SEM image, the synthesized nanoparticles had fine and irregular shapes with relatively smooth surfaces, as well as XRD spectrum showed that the crystalline size of Fe-doped TiO2NPs was 10.42 nm, furthermore, according to the DRS analysis, the bandgap energy of Fe-doped TiO2NPs was determined about 2.9 eV. The effects of operating parameters, including initial 2,4,6- TCP concentration, pH, contact time and Fe-doped TiO2NPs dosage on 2,4,6-TCP degradation were studied and optimized based on the response surface methodology with Box–Behnken method. The analysis of 2,4,6-TCP degradation showed that under optimum conditions, the removal efficiency reached 95.9% which is consistent with the model prediction. The optimum degradation conditions were as follows: pH, 3.29; initial 2,4,6-TCP concentration, 50.5 mg L–1; Fe-doped TiO2NPs dosage, 0.59 g L–1; and contact time, 55.7 min. The present results showed that Fe-doped TiO2NPs have great potential for removing 2,4,6-TCP from aqueous solutions.

Mesoporous silica such as MCM-41 was used as an adsorbent for the removal of cephalexin antibiotic from synthetic wastewater. In this study, MCM-41 adsorbent was synthesised and was characterised by FE-SEM, XRD, FTIR and isotherms of adsorption/desorption of N2. The effects of initial pH, adsorbent dose, initial adsorbate concentration, contact time and temperature on process efficiency were evaluated using Box-Behnken statistical experiment design (RSM). FTIR analysis revealed the Si-OH, H-O-H and Si-O-Si bonds are formed. According to BET surface area, MCM-41 had pores with a diameter of more than 2.0 nm and surface area of 1,097 m2g–1and also XRD spectra showed the mean crystallite size of MCM-41 was 75 nm. The statistical results show that pH, adsorbent dose, initial antibiotic concentration, temperature and quadratic pH were significant and presented with probability <0.05. The optimum removal condition based on analysis of variance and the quadratic model was the initial pH of adsorbate solution fixed at 3.00, adsorbent dose 800 mg L–1, the initial concentration of antibiotic at 50.0 mg L–1, a temperature of 40.0°C, and at the adsorption time of 30.0 min. Under these conditions, the percentage removal of cephalexin antibiotic was 90.3%. Therefore, according to the obtained results, the mesoporous silica can be used to adsorb cephalexin antibiotic in optimal conditions designed by response surface methodology.

AbstractThe aim of this study is to obtain optimal adsorption conditions for enrofloxacin (ENR) as a fluoroquinolone antibiotic onto NaOH-modified rice husk using response surface methodology (RSM). On the basis of a four variable Box–Behnken design (BBD), RSM was used to determine the effect of adsorbent dose (0.25, 0.5, and 0.75 g L−1), pH (5, 7, and 9), ENR initial concentration (25, 75, and 125 mg L−1), and temperature (15, 30, and 45°C) on adsorption efficiency. By applying the quadratic regression analysis, among the main parameters, the removal efficiency was significantly affected by all the four variables. The results showed that the predicted values for ENR adsorption were close to the experimental values and were in good agreement. In addition, the R2value (R2 = 0.9705) indicates that the regression is able to give a good predict of response for the adsorption process in the studied range. From the BBD predictions, the optimal conditions for 92.25% ENR removal were found to be 0.69 g L−1of adsorbent dose, pH 5.11, and initial concentration of ENR 25.02 mg L−1, at temperature 36.43°C.

The aim of this study is to obtain optimal adsorption conditions for enrofloxacin (ENR) as a fluoroquinolone antibiotic onto NaOH-modified rice husk using response surface methodology (RSM). On the basis of a four variable Box–Behnken design (BBD), RSM was used to determine the effect of adsorbent dose (0.25, 0.5, and 0.75g L−1), pH (5, 7, and 9), ENR initial concentration (25, 75, and 125 mg L−1), and temperature (15, 30, and 45°C) on adsorption efficiency. By applying the quadratic regression analysis, among the main parameters, the removal efficiency was significantly affected by all the four variables. The results showed that the predicted values for ENR adsorption were close to the experimental values and were in good agreement. In addition, the R2value (R2 = 0.9705) indicates that the regression is able to give a good predict of response for the adsorption process in the studied range. From the BBD predictions, the optimal conditions for 92.25% ENR removal were found to be 0.69g L−1of adsorbent dose, pH 5.11, and initial concentration of ENR 25.02 mg L−1, at temperature 36.43°C.

AbstractAt present, nanofiltration (NF) technologies find the ever greater use in the water industry, particularly, drinking water supplies. The concentrations of most anions in the groundwater sources are much higher than surface water and in some cases are higher than drinking water standards. In this regard, the aim of this study was to investigate the possibility of application of nanofilters in removing phosphate, fluoride, and nitrite from aqueous solutions. In this research, the effect of different factors including initial concentrations of nitrate, phosphate, and fluoride along with the flow rate were investigated. The results showed that with an increase in the initial concentrations of phosphate, fluoride, and nitrite, along with an increase in flow rate, the removal efficiencies decreased. The maximum removal efficiencies for phosphate, fluoride, and nitrite were 98, 82, and 87%, respectively. According to the findings, NF membrane could be recommended for removing nitrates, fluoride, and phosphate from aqueous solutions.

At present, nanofiltration (NF) technologies find the ever greater use in the water industry, particularly, drinking water supplies. The concentrations of most anions in the groundwater sources are much higher than surface water and in some cases are higher than drinking water standards. In this regard, the aim of this study was to investigate the possibility of application of nanofilters in removing phosphate, fluoride, and nitrite from aqueous solutions. In this research, the effect of different factors including initial concentrations of nitrate, phosphate, and fluoride along with the flow rate were investigated. The results showed that with an increase in the initial concentrations of phosphate, fluoride, and nitrite, along with an increase in flow rate, the removal efficiencies decreased. The maximum removal efficiencies for phosphate, fluoride, and nitrite were 98, 82, and 87%, respectively. According to the findings, NF membrane could be recommended for removing nitrates, fluoride, and phosphate from aqueous solutions.