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.

The aim of this study was to optimize the conditions of the Basic Blue 41 (BB41) adsorption on NaOH-modified rice husk (NaOH–RH) using response surface methodology based on Box–Behnken design. The three-level factors considered were pH (4, 7, and 10), initial concentration of BB41 (50, 75, and 100 mg L⁻¹), and adsorbent dose (0.025, 0.0875, and 0.15 g L⁻¹). Statistical analysis of result has shown that the predicted values for BB41 adsorption were close to the experimental values and were in a good agreement, on the other hand, the F-value (40.48), p-value (0.0004), and R² (0.9865) indicated that the regression is able to give a good prediction of response for the adsorption process in the range studied. According to the results, when the response was set in maximize and all the three factors were set in a range, the optimized values for BB41 adsorption were predicted as follows: pH value of 8.47, and BB41 initial concentration of 67.9 mg L⁻¹ and adsorbent dose of 0.12 g L⁻¹ for removal efficiency of 97.65%.