The Effects of Pre-treatments and Low-temperature Pyrolysis on Surface Properties of Biochar from Sunflower Straw as Adsorption Material

Abstract

Carbon adsorbent materials that were prepared from sunflower straw by a combination of pre-treatment and low-temperature pyrolysis showed better adsorption compared with untreated carbon. Four different pretreatment agents (steam, alkali (KOH), phosphoric (H3PO4), and salt (ZnCl2)) were analyzed with respect to their effects on the maximum surface area and the micropore area. Samples were measured by thermogravimetric analysis (TGA), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), surface area analysis, and pore size analysis. The surface area, pore volume, and N2-adsorption capacity of the samples were closely correlated with the pre-treating agent. A biochar with a maximum surface area of 877.6 m 2 /g and a micropore area of 792.8 m 2 /g was prepared with phosphoric acid (H3PO4) as the pre-treatment agent at a temperature of 400 °C. The main result of the one-stage pre-treatment procedure was the number of micropores. The two-stage, low-temperature pyrolysis procedure focused on the volume of the pores. Carbonized sunflower straw, with pretreated and lowtemperature pyrolysis procedures, was judged to be a highly effective and economic method to prepare carbon adsorbents.

Preparation of Activated Carbon From Sunflower Straw by H3PO4 Activation and Its Application for Acid Fuchsin Adsorption

“…2a showed the N2 adsorption-desorption isotherms of four SSAC. It could be seen from the figure that the four types of SSAC were basically in line with the characteristics of the type IV isotherm in the six physical adsorption isotherms divided by IUPAC (Sing et al 1985), and the adsorption isotherm tended to the Y axis under lower pressure, showed it was the H4 hysteresis loop, which was the typical feature of the material containing both micropores and mesopores (Zhang et al 2017). This could also be seen from the pore size distribution diagram in Fig.…”

“…The total pore volume increased with the increase of the impregnation ratio, while the micropore volume decreased, on the contrary the mesopore volume increased. The formation of the pores of the material is due to the oxygen-containing functional groups in the sunflower straw reacting with the phosphoric acid vapor generated by the activator H3PO4 at high temperature and the C atoms in the straw to form pores (Zhang et al 2017;Sun et al 2015), 4H3PO4+10C→P4+10CO+6H2O, 4H3PO4+10C→P4O10+6H2O, P4O10+10C→P4+10CO (Myglovets et al 2014). SSAC4 had the largest total pore volume (2.549 cm 3 /g), the smallest microporosity (2.07%), and an average pore diameter of 6.21 nm, which was conducive to the entry of macromolecular substances such as dyes into the pores.…”

“…As a large agricultural country, China produces a large amount of agricultural waste every year, and sunflower straw is one of the main sources. Taking September 2016 as an example, Chinese production is about 175.8 million tons of sunflower seeds, and 527.4 million tons of sunflower stalks could be produced according to the ratio of the output of sunflower stalks to sunflower in China (Zhang et al 2017). Most of these stalks are burned and deposited as farmland fertilizer, but the resulting PM2.5, SOx and NOx will pollute the atmosphere (Yang et al 2020).…”

Synthesis, Characterization, and Dye Removal of ZnCl2-Modified Biochar Derived from Pulp and Paper Sludge

“… 11 , 12 The composition of biomass, heating rate, setting temperature, and residence time of the pyrolysis process and modified method all have a great influence on biochar properties. 13 , 14 …”

A novel and low-cost CuPc@C catalyst derived from the compounds of sunflower straw and copper phthalocyanine pigment for oxygen reduction reaction

“…Therefore, it can be inferred that the CuPc particles begin to decompose at 850 , and the decomposition has been completed by 900 , accompanied by the fracture of the carbon ring. According to JCPDS, the CuPc@C series composite catalysts also contain SiO 2 (JCPDS# 78-1419) impurities, 36 which are mainly derived from CuPc pigments. The presence of SiO 2 can prevent the precipitation of CuPc pigments and play a role in dispersion, which is more conducive to the composite of sunower straw carbon nanosheets and CuPc particles.…”