Novel ternary nanocomposite (TiO2@Fe3O4-chitosan) system for nitrate removal from water: an adsorption cum photocatalytic approach

• Published in: Environmental science and pollution research international 2024-08, Vol.31 (38), p.50670-50685
• Main Authors: Venu Sreekala, Smitha, George, Jilsha, Thoppil Ramakrishnan, Resmi, Puthenveedu Sadasivan Pillai, Harikumar
• Format: Article
• Language: English
• Subjects: adsorbents; Adsorption; Anions; Anthropogenic factors; Aquatic Pollution; Atmospheric Protection/Air Quality Control/Air Pollution; Chitosan; Continuous flow; coprecipitation; Earth and Environmental Science; Ecotoxicology; Efficiency; Environment; Environmental Chemistry; Environmental Health; Environmental perception; Field emission; Flow rates; Flow velocity; Fourier analysis; Fourier transform infrared spectroscopy; Fourier transforms; Functional materials; gels; Groundwater; Groundwater treatment; Infrared analysis; Iron oxides; Nanocomposites; Nitrate removal; Nitrates; Nitrogen removal; Nutrient removal; Photocatalysis; photocatalysts; Research Article; Scanning electron microscopy; Silver; Sol-gel processes; solar radiation; Structure-function relationships; surface area; synergism; Synergistic effect; Titanium; Titanium dioxide; Transmission electron microscopy; ultraviolet-visible spectroscopy; Waste Water Technology; Water analysis; Water Management; Water pollution; Water Pollution Control; Water resources; Water sampling; Water treatment; X-ray diffraction
• ISSN: 1614-7499; 0944-1344; 1614-7499
• DOI: 10.1007/s11356-024-34553-7

Nitrate pollution of water emerging from various anthropogenic activities has become a major environmental concern because of its deleterious effects on natural water resources. The present work deals with the synthesis of the ternary nanocomposite based on chitosan, iron oxide (Fe 3 O 4 ), and titanium dioxide (TiO 2 ) and its application for the removal of nitrates from model-contaminated water. Fe 3 O 4 derived through a coprecipitation method was incorporated into the chitosan matrix which was fabricated in the form of beads. The wet gel beads were then successfully coated with sol–gel-derived silver-doped titanium dioxide sol followed by drying under suitable conditions to get the functional nanocomposite beads. The synthesized functional materials were further characterized for their structural, morphological, and textural features using X-ray diffraction analysis, physical property measurement (PPMS), Fourier transform infrared (FTIR) analysis, UV visible spectroscopy analysis (UV–vis), BET surface area analysis (BET), field emission scanning electron microscopic (FESEM), and transmission electron microscopy (TEM) analysis. The ternary nanocomposites were further used for the removal of nitrates via adsorption cum photocatalytic reduction technique from the model contaminated water when subjected to an adsorption study under dark conditions and photocatalytic study under UV/visible/sunlight for a definite time. Fe 3 O 4 in the nanocomposite provides enhanced adsorption features whereas the functional coating of titanium dioxide aids in the removal of nitrates through the photocatalytic reduction technique. The functional beads containing 3% Fe 3 O 4 in the wet gel form (CTA-F3) have excellent nitrate removal efficiency of ~ 97% via adsorption cum solar photocatalysis towards the removal of nitrate ions from 50 ppm nitrate solution, whereas the dried nanocomposite beads have got a nitrate removal efficiency of ~ 68% in 1 h from 100 ppm nitrate solution. Continuous flow adsorption cum photocatalytic study was performed further using the oven-dried functional beads in which flow rate and bed height were varied while maintaining the concentration of feed solution as constant. A nitrate removal efficiency of 65% and an adsorption capacity of 4.1 mgg −1 were obtained for the CTA-F3 beads in the continuous flow adsorption cum photocatalysis experiment for up to 5 h when using an inlet concentration of 100 ppm, bed height 12 cm, and flow rate 5.0 ml min −1