Fabrication and characterization of halloysite nanotube thin film nanochomposite membrane for salt and dye removal

Recently, water has become one of today's most valuable resources. The rapid increase in the human population and the negative changes in the environment are the cause of water scarse. Thus, recycling of water has become important for both domestic and industrial wastewater. Membrane technologies are attempting to serve this purpose by conducting new researches to develop new techniques. Membrane systems are more preferred over the last years due to their continuous operation, small space requirements, modular application, very high concentrations, transportability, no construction required, and the cost is getting shorter day by day. In the treatment of industrial wastewater, cleaner and more economical technologies are required as well as traditional methods. Membrane technologies are considered as a solution for these requirements. In this study, flat sheet membranes were produced using interface polymerization method at the level of nanofiltration with HNT addition. The addition of hallosyt nanotubes (HNT) is aimed to increase both flux, salt and dye removal efficiencies in the membranes. Ultrafiltration membranes containing polysulfone (PSf), polyvinylpyrrolidone (PVP) as polymer and dimethylformamide (DMF) as solvents were produced by phase inversion method in the production of nanofiltration membranes. Interfacial polymerization was carried out on the ultrafiltration membranes by the thin film composite method, and nanofiltration membranes with Hallosite nanotube (HNT) were prepared at 4 different concentrations of 0%, 0.02%, 0.04%, 0.06%. Various characterizations were made with these membranes by permeability, salt and dye removal, Zeta potential, FTIR analysis, contact angle, SEM analysis, optical profilometer and surface roughness analyzes. Performance tests of nanofiltration membranes were evaluated with pure water and MgSO4 and NaCl salts at 2000 ppm concentration. The flux values were recorded under 4 different pressures (6, 9, 12, 15 bar) for 1 hour. Input and output values were read by the conductivity meter and efficiency calculations were made. Treatment attempts with nanofiltration membranes were first conducted by preparing two different types of dye in their treatment works; Red dye (Setazol Red 3B) and Orange dye (Reactive Orange 16). These dyes were prepared at a concentration of 100 ppm and worked under four different pressures which are 6, 9, 12 and 15 bars. When the dyes are ready, the samples are taken and the absorbance values of the input and output samples are read in the UV-Spectrophotometer for wavelength scanning. At the end of all these experiments, temperature and pH experiments were performed with HNT nanofiltration membrane, which is believed to perform better compared to others. Pure water, setazol red and reactive orange dyes were tested at three different temparatures (15 ° C, 25 ° C 40 ° C), three different pH (pH 4, pH 8 and pH 11) and four different pressure. It has been observed that, by this method, the flux and efficiency is changed with the change of temperature and pH. Characterization results When pure membranes and HNT membranes are compared, - According to the Zeta Potential results, the membrane surfaces are negative, but the addition of HNT did not increase the negative, reduced it in some amount. - As the HNT ratio increases, the contact angle increases and the hydrophilicity decreases. These results show that the surface roughness of HNT tubes added to interfacial polymerization affects surface roughness. - The surface roughness of TFN membrane with 0.04% HNT ratio was found higher than the other membranes with different HNT ratios. - According to the permeability results, the addition of HNT generally improved the flux performance, but a decrease of 0.06% HNT was observed again. The best flux performance was achieved at 0.04% HNT. - The filtration experiment with 2000 ppm MgSO4 divalent ion salt shows that the membrane has the highest concentration of 0.04% HNT. It has been found that the HNT addition does not significantly change the efficiency as well as the flow increase. - In the filtration experiment with 2000 ppm NaCl monovalent ion salt, it was observed that the membrane had the highest concentration of 0.04% HNT in the flow but the rejection efficiency decreased. Dye performance results - For both Setazol Red and Reactive Orange, the best performance in flow was achieved with 0.04% HNT. Rejection efficiencies are above 99%. Dye performance results at different temperature and pH ranges - When pure water temperature performances obtained with pure TFC NF membrane and 0.04% HNT TFN NF membrane are examined, it is seen that as temperature increases, flux performance also increases. -When the dye performance results for setazol red and reactive orange obtained with the pure TFC NF membrane and 0.04% HNT TFN NF membrane were taken into consideration, it was found that the flow rate increased with temperature but no decrease in the efficiency. - Setazol red dye performance results for pure TFC NF membrane show a decrease in the flow from pH 4 to pH 11. For the 0.04% HNT TFN NF membrane, the flux increased from pH 4 to pH 8, while at pH 11 a significant decrease in flux was observed. The reason for this is that the 0.04 HNT TFN NF membrane at different pH values is more positive than the pure TFN NF membrane. -The results for setazol red is same with reactive orange. For the pure TFC NF membrane, the reactive orange dye performance showed a decrease in the flow from pH 4 to pH 11, while for the 0.04% HNT TFN NF membrane the flux increased from pH 4 to pH 7, while a significant decrease in the flow was observed at pH 11. Efficiency has not changed. As a result, the positive effect of the HNT addition on the membrane was observed. It has been observed in this study that a high flux and good removal efficiency can be achieved in textile wastewater treatment with high temperature and optimum pH range.