Adsorption of nitrate from aqueous solution with ZSM-5/Fe nanosorbent based on optimizing of the isotherms conditions before determination by UV-Vis Spectrophotometry

The life-threatening nature of high nitrate concentrations in various water resources motivated the present study to investigate the nitrate adsorption by ZSM-5 nanozeolite and the feasibility of increasing nitrate removal efficiency using iron-doped ZSM-5 (ZSM-5/Fe) nanoadsorbent. The optimal adsorption conditions were determined first by modeling the central composite design (CCD) using Design Expert.7 software based on four influential factors of contact time, pH, adsorbent dosage and initial nitrate concentration. Then, the isotherms of nitrate adsorption under optimized conditions were investigated using the degree of fit of experimental data with Langmuir and Freundlich models for mathematical modelling of the nitrate adsorption process. Based on the test design results, the highest nitrate removal efficiency (%93.1) was determined with UV-Vis spectrophotometry at the contact time of 150 min, pH value of 3, the adsorbent dosage of 4 g L-1 and initial concentration of 40 mg L-1. Analysis of adsorption isotherms also confirmed the greater fit of the experimental data with the Freundlich equation, so that the correction factor of the Freundlich equation was greater than the Langmuir equation, due to the heterogeneous distribution of active sites for adsorption on the ZSM-5/Fe nanosorbent surface. Therefore, it can be concluded that ZSM-5/Fe is a high efficiency nanosorbent for nitrate removal from water resources.