Preparation of hierarchical self-assembled SiO2/ZnO composite by low-temperature hydrothermal approach for enhanced adsorption of 4-nitrophenol and dyes

Abstract

Here, we initially fabricated the hierarchical SiO2/ZnO nanospheres via a facile low temperature (LT) 90 °C hydrothermal approach and the prepared SiO2/ZnO nanospheres show an excellent surface area of about 1280.8 m2/g. The prepared composite has been investigated for the removal of mixture of cationic (rhodamine B, crystal violet, methylene blue) and anionic dyes (congo red, methyl orange) to understand the industrial point of view. On the basis of the selectivity test, a detailed study has been carried out for the removal of organic pollutant Rhodamine B, and the effect of pH, contact time, initial dye concentration, and adsorbent dosage were among the optimal parameters that led to the maximum RhB adsorption (pH-11, 10 min, and 5 mg of adsorbent). It has been noticed that SiO2/ZnO shows an impressive adsorbent property for basic cationic dyes. The ability of the SiO2/ZnO adsorbent to be reproduced and reused was evaluated. Furthermore, the produced adsorbent was known to adhere to pseudo-second-order kinetics and the Langmuir isotherm with R2 = 0.96 and R2 = 0.98, respectively. The catalytic property of the prepared material was also tested for 4-nitrophenol reduction using NaBH4. The adsorption capacity (max.) for the removal of RhB was reported to be 83.33 mg/g, and on the other hand, 4-NP was 89% removed by the prepared adsorbent. The experiments confirmed that the processed nanocomposite can successfully eliminate organic pollutants, implying the practical applicability of the material for waste-water remediation.