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Abstract Background and purpose: Natural zeolites are widely used for the purification of water and wastewater. Nevertheless the selectivity of clinoptilolite (a common zeolite mineral) for cadmium is known to be particularly low. In order to enhance the zeolites’ sorption capacity for cadmium, we treated natural clinoptilolite with sulfuric acid solutions and investigated the sorption of cadmium to acid-modified clinoptilolite by a series of batch experiments. Materials and methods: The batch method has been employed using metal concentrations in solution ranged from 25 to 100 mg/l and adsorbent ranged from 0.2 to 1.8 g/l. The influence of acid concentration, contact time, solution pH, adsorbent particle size, initial cadmium concentration and adsorbent mass has been studied. Results: It was found that the acid modified clinoptilolite exhibits higher adsorption to cadmium than unmodified clinoptilolite and adsorption of the cadmium is influenced by several parameters such as cadmium initial concentration, adsorbent dosage and solution pH. Maximum absorption efficiency was achieved at pH of 6. Meanwhile maximum absorption efficiency of acid modified clinoptilolite in cadmium removal shows improvement due to 1 molar sulfuric acid. The equilibrium adsorbed amount also increased with the initial concentration of the metal ions, as expected. Adsorption capacities of the acid- modified clinoptilolite for cadmium increased as the particle size decreased down to 0.5 mm in diameter, but no difference was observed for a diameter less than 1.5 mm. Conclusion: The best results in terms of efficiency are obtained for the clinoptilolite modification with 1 molar sulfuric acid and it was more favorable than natural clinoptilolite in removing cadmium and thus was a better adsorbent as low-cost alternatives in wastewater treatment for cadmium removal.

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Background and purpose: Fluoride in drinking water can be either beneficial or detrimental to health depending on its concentration. Its high concentrations leads to dental and skeletal fluorosis and lesions of the endocrine glands, thyroid and liver. This paper describes the removal of fluoride from water using lemna minor. Material and methods: This research was a lab study. The lemna minor plants were collected and dried in the oven at 105 in 24 h and sieved in 18-30 mesh. The optimum values of pH, contact time and adsorbent dosage were determined and the different concentrations of fluoride were experimented in lab scale conditions for modified lemna minor. The fluoride concentration was measured in wavelength of 518 nm by spectrophotometer. Also, the found data of this research were fitted with Variety Isotherm and kinetic models. Results: The results showed that by increasing pH solution, removal efficiency decreased and optimum pH was 5. Increasing of contact time and adsorbent dose can lead to the increase of the removal efficiency.Adsorption isotherm data show that the fluoride sorption followed the Langmuir No 2. Fluoride sorption is better agreed with pseudo- second order of Kinetics model which was well described by pseudo- second order model. Conclusion: The result of the present work shows that lemna minor can be used as an effective and cheap adsorbent for fluoride removal.

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Background and purpose: Continuous input of antibiotics to the environment causes many problems such as antibiotic resistance in pathogenic microorganisms. Therefore, researchers are aiming to find solutions to reduce antibiotics in hospital effluents and polluted waters. Amoxicillin is an antibiotic which is widely used to treat infections. Due to inappropriate use it enters the wastewater and finally the environment in almost unmetabolized form. This study was conducted to evaluate the performance of multi-walled carbon nanotubes for Amoxicillin removal from aqueous solutions. Materials and methods: In this study the efficacy of multi-walled carbon nanotubes for the removal of amoxicillin was investigated in a batch system considering pH (10-4), ionic strength (0 to 0.1 mol/ L sodium chloride), and adsorbent dose (0.4 – 1.8 g /L). Finally, isotherms and kinetics of the adsorption was analyzed. Results: The results showed that the maximum removal of amoxicillin occurred at pH 8. Also, increase in the ionic strength decreased the removal efficiency while increase in the adsorbent dose increased the removal efficiency. The equilibrium adsorption isotherm data well fitted with Langmuir model (R2= 0.9108) and adsorption kinetics fitted with pseudo second order model. Conclusion: According to the results multi-wall carbon nanotubes could be assumed as an acceptable adsorbent for Amoxicillin removal in the aquatic solutions.

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Background and purpose: Dyes in textile wastewater are amongst the main sources of environmental pollutants that are harmful for environment and human health. This study was designed for experimental evaluation of Reactive Blue 19 absorption from aqueous solutions by dried powder, modified powder, and modified carbon derived from Azolla aquatic plant carbon filiculoides, as a low cost adsorbent.

Materials and methods: In this experimental laboratorial study the effects of various parameters (initial dye concentration, contact time, pH and, amount of adsorbent (on the dye removal efficiency was investigated. Then the isotherm, kinetic, and thermodynamic equations were done. Measuring the amount of dye concentration was determined using a spectrophotometer at a wavelength of nm 594. Adsorbent characteristics were analyzed using SEM, FTIR, and BET techniques. Statistical analysis was done by Excel software.

Results: The highest absorption capacity were 4.83 mg/g by modified powder, 4.55 mg/g by dried powder, and 4.15 mg/g by modified carbon which were observed in optimum conditions: pH=2, equilibrium time of 60 min, 10 g/L of adsorbent, and initial dye concentration of 5 mg/l. The absorption efficiency of Azolla filiculoides increased by increasing the adsorbent dose and contact time, and decreasing the initial concentration of dye. It was found that the adsorption process followed Lungmuir isotherm and the kinetic model of pseudo second-order. The maximum absorbance of dye occurred by modified powder of Azolla filiculoides.

Conclusion: According to our results, adsorption process by Azolla aquatic plant is an efficient and affordable method for removal of dyes from textile industry wastewater.