Eco-friendly synthesis of amino and carboxyl-functionalized silica nanoparticles for enhanced adsorption of water pollutants

Abstract

Green synthesised nanoparticles (NPs) have garnered significant attention as a rapidly expanding category of materials with diverse applications. In this context, plants are widely acknowledged as a highly favourable option for green synthesis due to their adherence to the eco-friendly pathway of NPs biosynthesis. The objective of green synthesis is to reduce the utilisation of hazardous chemicals. The utilisation of silica (SiO2) NPs, synthesised from biomass as adsorbents, has shown great potential particularly in removing toxic materials from environment. When it comes to adsorbing water pollutants, functionalized SiO2 NPs are seen as potential option. However, certain functional group onto the surface of SiO2 NPs have higher affinity towards a particular pollutant. In this work, a simple and eco-friendly synthesis method (using waste bamboo leaves) have been utilised for production of SiO2 NPs. Further, a silylating procedure was used to functionalize SiO2 NPs with amine (A-SiO2) and carboxyl groups (C–SiO2) for determining adsorption capabilities towards anionic and cationic dyes i.e., Naphthol green-B (NGB) and brilliant green (BG). The adsorption mechanism has been discussed in view of different adsorption isotherm models. According to batch investigations, the functionalized SiO2 NPs showed different behaviour for dyes depending upon nature of dyes and the functional groups. The results of the study revealed that A-SiO2 NPs were having adsorption capacity of 122.10 mg/g for anionic dye (NGB) while C–SiO2 NPs showed adsorption capacity of 114.41 mg/g for cationic dye (BG). Additionally, these NPs exhibit good recyclability up to 5 cycles of reuse. Novelty of this study is the reduced energy needs for the green synthesis of the SiO2 NPs using bamboo leaves and the effect of different functional groups on the adsorption capacity of the NPs. Overall, this study provides a sustainable, and reusable approach for effective dye removal from wastewater, addressing both environmental and economic problems.