Biochar Derived from Agricultural Wastes as a Means of Facilitating the Degradation of Azo Dyes by Sulfides

Abstract

Dyes are common contaminants, some of which are teratogenic, carcinogenic, and causative of ecological damage, and dye wastewater often contains toxic sulfides. Biochar has been widely used for the adsorption and catalysis degradation of pollutants, including dyes and sulfides, due to its abundant surface functional groups and large specific surface area. Therefore, the simultaneous treatment of dyes and sulfides with biochar may be a feasible, effective, and novel solution. This study sought to utilize low-cost, environmentally friendly, and widely sourced biochar materials from agricultural wastes such as corn stalk, rice chaff, and bean stalk to promote the reduction of dyes by sulfides. Through the action of different biochars, sulfides can rapidly decompose and transform oxidizing dyes. The RCB800 (rice chaff biochar material prepared at 800 °C) was observed to have the best effect, with a degradation rate of 96.6% in 40 min and 100% in 50 min for methyl orange. This series of materials are highly adaptable to temperature and pH, and the concentration of sulfides has a significant effect on degradation rates. Compared with commercial carbon materials, biochars are similar in terms of their catalytic mechanism and are more economical. Scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption and desorption characterization results indicated that biochar contains more pores, including mesopores, and a sufficient specific surface area, both of which are conducive to the combination of sulfides and dyes with biochar. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy showed that there are oxygen-containing functional groups (examples include quinones and carboxyl groups) on the surface of biochar that promote the reaction of sulfide and dye. The formation of active polysulfides also potentially plays an important role in the degradation reaction. This article outlines a new method for improving the degradation efficiency of azo dyes and sulfides via biochar materials derived from widely sourced agricultural wastes.

Characteristics and agrarian properties of biochar derived from pyrolysis and co-pyrolysis of rubberwood sawdust and sewage sludge for further application to soil improvement

“…pH levels of RWSB and SSB in this study are comparable or similar to previous studies by Angın (2013), Ferreira et al (2019 and Reza et al (2020). On the other hand, Han et al (2021) reported that the low pH of biochar can be relatively in uence, because of the hydrogen H + ions engaged the biochar adsorption pour sites. Biochar with higher pH has more potential for use as soil conditioner that reduces heavy metal contaminants.…”

Redox properties of nano-sized biochar derived from wheat straw biochar

“…27,28 Toxic sulde contaminants are also present in dye wastewater, as they are used as dyeing auxiliaries with azo dyes; thus, they are also common reducing agents in the natural environment. 29 They can moderate azo dye contaminants in wastewater, but the reaction rate is very slow. Therefore, BC of different particle sizes was used to mediate the redox reaction between azo dyes and suldes in the present study.…”

Fabricating Cationic Lignin Hydrogels for Dye Adsorption

“…Anion dyes are widely used in the dyeing process due to their simple synthetic process, low cost, and better staining performance [3,4]. During the process of anionic dyeing, the fabric needs to be washed several times to improve its dyeing fastness, resulting in the generation of a large amount of anionic dye wastewater [5], causing oxygen deficiency and jeopardizing the viability of aquatic animals and plants [6,7].…”