Adsorption by activated alumina is considered to be one of the most practiced methods for defluoridation of freshwater. This study was conducted, therefore, to investigate the effect of natural organic matters (NOMs) on the removal of fluoride by activated alumina using response surface methodology. To the authors' knowledge, this has not been previously investigated. Physico-chemical characterization of the alumina was determined by scanning electron microscope (SEM), Brunauer-Emmett-Teller (BET), Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence (XRF), and X-ray diffractometer (XRD). Response surface methodology (RSM) was applied to evaluate the effect of single and combined parameters on the independent variables such as the initial concentration of fluoride, NOMs, and pH on the process. The results revealed that while presence of NOM and increase of pH enhance fluoride adsorption on the activated alumina, initial concentration of fluoride has an adverse effect on the efficiency. The experimental data were analyzed and found to be accurately and reliably fitted to a second-order polynomial model. Under optimum removal condition (fluoride concentration 20 mg/L, NOM concentration 20 mg/L, and pH 7) with a desirability value of 0.93 and fluoride removal efficiency of 80.6%, no significant difference was noticed with the previously reported sequence of the co-exiting ion affinity to activated alumina for fluoride removal. Moreover, aluminum residual was found to be below the recommended value by the guideline for drinking water. Also, the increase of fluoride adsorption on the activated alumina, as NOM concentrations increase, could be due to the complexation between fluoride and adsorbed NOM. Graphical abstract ᅟ.
Azo dyes are mostly toxic and carcinogenic and cause harm to humans and the environment. This study was conducted to investigate the degradation of azo dye acid red 14 (AR14) from aqueous solution using hydrogen peroxide (H2O2)/nano zerovalent iron (nZVI) and persulfate (S2O82–)/nZVI processes in the presence of ultraviolet (UV) irradiation. This experimental study was carried out in a laboratory‐scale batch photoreactor with a useful volume of 1 L. The nZVI was synthesized by the sodium borohydride (NaBH4) reduction method. In these processes, the effects of parameters including initial pH, H2O2 concentration, S2O82– concentration, nZVI dose, concentration of AR14 dye, and reaction time were studied. The results showed that decolorization increased by increasing the nZVI dosage, H2O2 and S2O42‐ concentrations, and reaction time, or decreasing dye concentration and pH. However, a too high oxidant concentration (H2O2 and S2O42‐) could inhibit the degradation. The experimental conditions for degradation of AR14 by UV/S2O82‐/nZVI and UV/H2O2/nZVI processes were as follows: [H2O2] = 10 mM, [S2O82–] = 8 mM, AB14 dye = 100 mg/L, pH = 3, and nZVI dose = 0.05 g. Under these conditions, the highest removal efficiencies of AR14, chemical oxygen demand (COD), and total organic carbon (TOC) for the UV/S2O82–/nZVI process were 93.94%, 86.5%, and 81.6%, respectively, while these values were 89.3%, 79.57%, and 72.9% for the UV/H2O2/nZVI, respectively. Also, the average oxidation state (AOS) was decreased from 2.93 to 2.14 in the effluent of the UV/S2O82–/nZVI process and from 2.93 to 2.2 for the UV/H2O2/nZVI process. The results showed that the ratio of biochemical oxygen demand (BOD5) to COD in the effluents of the UV/S2O82/nZVI and UV/H2O2/nZVI processes after 90 min was 0.63 and 0.74, respectively. These findings suggest biodegradability improvement. Practitioner points Photocatalytic degradation of azo dye Acid Red 14 (AR14) was achieved using H2O2/nZVI and S2O82–/nZVI processes in the presence of UV irradiation. Effects of operating parameters on photocatalytic degradation AR14 dye were evaluated in the UV/H2O2/nZVI and UV/S2O82–/nZVI processes. Biodegradability and mineralization studies of AR14 dye photocatalytic degradation were performed for the UV/H2O2/nZVI and UV/S2O82–/nZVI processes.
Nowadays, the presence of antibiotics in the environment has been identified as an important concern for the various life cycle. Thus, this study was conducted to evaluate ciprofloxacin (CIP) adsorption efficiency onto the multi-walled carbon nanotube (MWCNTs) and magnetic multi-walled carbon nanotube (MMWCNTs). In this experimental study, the characteristics of the studied adsorbents were determined using SEM, FTIR and XRD methods. The effects of operational parameters including contact time (10–120 min), initial concentration of CIP (10–100 mg/L), adsorbent dosage (0.1–1 g/L) and pH (3–9) were evaluated. The isotherm and kinetics studies of the CIP adsorption onto the studied adsorbents were also carried out. The adsorption efficiency increases by increasing the contact time and adsorbent dosage, while it increased by increasing the CIP initial concentration. The results showed that higher CIP adsorption efficiency was observed at pH = 7, adsorbent dosage of 0.5 g/L, CIP concentration of 30 mg/L and contact time of 120 min. The isotherm and kinetics studies revealed that the CIP adsorption data were better described by the Langmuir isotherm model and pseudo-second-order kinetics equation model. It can be concluded that both of these adsorbents have suitable potential to remove the CIP from aqueous solution but this ability is greater in MMWCNTs.
Background and Aim: Dyes are one of the most important pollutants in textile wastewater (TWW). Use of advanced oxidation processes (AOPs) as an efficient method can be useful for removal of these pollutants from the effluent of textile wastewater. In this study we evaluated the efficiency of the persulfate activation process, using ultraviolet (UV), in the presence of granular activated carbon (GAC) for removal of methylene blue dye (MBD). Also, we studied the effect of operating parameters on the dye removal. Materials and Methods: This experimental study was performed in a pilot-scale batch photoreactor. The effect of operating parameters including solution pH (between 3 and 9), dosage of granular activated carbon (0.6-5 mg/L), persulfate concentration (0.2-2 mmol/L), initial concentration of methylene blue dye (50-400 mg/L), and contact time (2-30 minutes) were evaluated. The final concentration of methylene blue dye was measured by using DR-6000 device. Mineralization of the process, in optimal conditions, was determined by measuring COD and TOC. Results: The highest efficiency of the process for removal of methylene blue dye (99% dye removal at an initial concentration of 50mg/L) was observed at pH = 3, granular activated carbon dose of 1 g/L, optimal persulfate concentration of 1 mmol/L, and after a 20-minute contact time. The removal rates of COD and TOC were 71% and 69.9%, respectively, and the decomposition rate of methylene blue dye was based on the first-order reaction (R 2 = 0.99). Conclusion:Considering the results of this study, the combined process had a significant efficiency to remove methylene blue dye and can be used as an efficient method for removal of the dye from the effluent of textile wastewater.
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