Abstract
To develop a new adsorbent for removal of nitrate and to enhance the adsorbent separation from aqueous solution, surface modification of titanium dioxide nanoparticles with nano-zero-valent iron (nZVI) was performed through chemical coprecipitation of magnetic nanoparticles on TiO2 surface. Morphological, structural and magnetic properties of modified adsorbents (TiO2/nZVI) were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared radiation (FTIR) and vibrating sample magnetometer (VSM). To determine the ionic strength effect and optimal removal conditions, the effect of contact time (60–210 min), pH (4–10) and adsorbent dosage (0.5–1.5 g/L) on adsorption efficiency were studied, using response surface method. Obtained results showed that the nitrate removal efficiency decreased with increasing ionic strength. The TiO2/nZVI nanocomposites exhibited a ferromagnetic behavior and its saturation magnetization was 795.28 memu/g. The maximum nitrate removal (98.226%) achieved by modified TiO2 was about 14.65% higher than the unmodified nanoparticles. The optimized adsorption parameters were: adsorbent dosage 0.982 g/L, pH 4.185 and the contact time 150.091 min.
Highlights
Nitrate is often found in drinking water because of human activities such as excessive utilization of chemical fertilizers, inappropriate disposal of industrial, human and animal wastes, etc
transmission electron microscopy (TEM) images taken from T iO2/nano-zero-valent iron (nZVI) magnetic nanoparticles are shown in Fig. 1e, f
Comparison of the obtained results showed that the maximum adsorption by modified TiO2 was about 14.65% higher than the unmodified nanoparticle; this is due to the increased adsorbent surface and the high ability of zero-valent iron nanoparticles integrated with T iO2 for removal of pollutants [20, 25, 57]
Summary
Nitrate is often found in drinking water because of human activities such as excessive utilization of chemical fertilizers, inappropriate disposal of industrial, human and animal wastes, etc. Conventional nitrate removal technologies including ion exchange, reverse osmosis, electrodialysis, biological and chemical denitrification, are often costly and complex with low efficiency and sub-products [2,3,4,5]. Adsorption has been proposed as an attractive technology for removal of different pollutants from water due to its process simplicity, selectivity and reusability of the adsorbent, low cost and environment-friendly nature [6,7,8,9,10,11,12,13,14]. Khezri et al [15] investigated the adsorption of nitrate anions from aqueous solutions on ammonium-functionalized magnetic mesoporous silica. Zhao et al [13] reviewed the recent
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