Biogenic Nanosilica Synthesis Employing Agro-Waste Rice Straw and Its Application Study in Photocatalytic Degradation of Cationic Dye

Garima Singh,Hossein Beidaghy Dizaji,Hariprasad Puttuswamy,Satyawati Sharma

doi:10.3390/su14010539

Abstract

The current study aims towards a holistic utilization of agro-waste rice straw (RS) to synthesize nanosilica (SiNPs) employing the sol–gel method. The effect of ashing temperature was evaluated for the synthesis process. X-ray diffraction demonstrated a broad spectrum at 21.22° for SiNPs obtained using RSA-600, signifying its amorphous nature, whereas crystalline SiNPs were synthesized using RSA-900. The EDX and FTIR spectra confirmed the significant peaks of Si and O for amorphous SiNPs, confirming their purity over crystalline SiNPs. FE-SEM and TEM micrographs indicated the spheroid morphology of the SiNPs with an average size of 27.47 nm (amorphous SiNPs) and 52.79 nm (crystalline SiNPs). Amorphous SiNPs possessed a high surface area of 226.11 m2/g over crystalline SiNPs (84.45 m2/g). The results obtained attest that the amorphous SiNPs possessed better attributes than crystalline SiNPs, omitting the need to incorporate high temperature. Photocatalytic degradation of methylene blue using SiNPs reflected that 66.26% of the dye was degraded in the first 10 min. The degradation study showed first-order kinetics with a half-life of 6.79 min. The cost-effective and environmentally friendly process offers a sustainable route to meet the increasing demand for SiNPs in industrial sectors. The study proposes a sustainable solution to stubble burning, intending towards zero waste generation, bioeconomy, and achieving the Sustainable Development Goals (SDGs), namely SDG 13(Climate Action), SDG 3(Good health and well-being), SDG 7(use of crop residues in industrial sectors) and SDG 8 (employment generation).

Highlights

Publisher’s Note: MDPI stays neutralRice straw (RS), lignocellulosic biomass, is a very common agro-waste generated in the agriculture system after the post-harvesting of rice
The synthesis process of silica nanoparticles (SiNPs) carried out using RSA-600 depicted a broad peak centered at 22◦ ; the absence of any other peaks confirmed the SiNPs to be of amorphous nature (Figure 2C)
The study revealed that rice straw (RS) combusted at 600 ◦ C served as an ideal condition for synthesizing amorphous SiNPs

Summary

Introduction

Rice straw (RS), lignocellulosic biomass, is a very common agro-waste generated in the agriculture system after the post-harvesting of rice. Incorporating the crop and harvesting method, approximately 40–60% of residual biomass comprises RS [1,2]. RS is a stiff, voluminous lignocellulosic biomass with significant silica (SiO2 ) deposits, for which the level of biogenic silica can reach up to 82% on a dry weight basis. Easy and cheap process, most farmers opt for open field-burning as the most preferred approach to dispose of RS in agricultural fields [3,4]. The burning of farm waste causes the ghastly pollution of soil and water at the regional scale. This practice adversely reduces the nutrient composition in the soil

Methods

Results

Conclusion