Preparation and Characterization of MgO-Modified Rice Straw Biochars.

Xianxian Qin,Yunlin Fu,Zhigao Liu,Jixin Luo

doi:10.3390/molecules25235730

Abstract

Rice straw is a common agricultural waste. In order to increase the added value of rice straw and improve the performance of rice straw biochar. MgO-modified biochar (MRBC) was prepared from rice straw at different temperatures, pyrolysis time and MgCl2 concentrations. The microstructure, chemical and crystal structure were studied using X-ray diffraction (XRD), a Scanning Electron Microscope (SEM), Fourier transform infrared spectroscopy (FTIR), nitrogen adsorption desorption isotherms and Elementary Analysis (EA). The results showed that the pyrolysis temperature had significant influence on the structure and physicochemical property of MRBCs. MRBC-2 h has the richest microporous structure while MRBC-2 m has the richest mesoporous structure. The specific surface area (from 9.663 to 250.66 m2/g) and pore volume (from 0.042 to 0.158 cm3/g) of MRBCs increased as temperature rose from 300 to 600 °C. However, it was observed MgCl2 concentrations and pyrolysis time had no significant influence on pore structure of MRBCs. As pyrolysis temperature increased, pH increased and more oxygen-containing functional groups and mineral salts were formed, while MgO-modified yield, volatile matter, total content of hydrogen, oxygen, nitrogen, porosity and average pore diameter decreased. In addition, MRBCs formed at high temperature showed high C content with a low O/C and H/C ratios.

Highlights

For sustainability cause, rice straw is an ideal raw material for biochar because of its large production in China [1,2]
The preparation of rice straw into biochar is one of the methods that has been heatedly discussed by people in recent years: it can reduce the amount of released solid particulates and smoke during the traditional process, such as composting and incineration [4]
Rice straw biochar (RBC) produced by slow pyrolysis filled with nitrogen to maintain the hypoxic conditions and at a temperature of 300 ◦ C at a heating rate of 8 ◦ C min−1 for a retention time of 1 h

Summary

Introduction

Rice straw is an ideal raw material for biochar because of its large production in China [1,2]. Large amounts of rice straw are abandoned every year and they are dominantly burned. It is case the loss of resources, and the production of carbon monoxide, sulfur dioxide and other gases, causing environmental pollution problems [3]. The preparation of rice straw into biochar is one of the methods that has been heatedly discussed by people in recent years: it can reduce the amount of released solid particulates and smoke during the traditional process, such as composting and incineration [4]. Biochar increases plant photosynthesis and nutrient absorption and improves soil water retention [9]. Biochar can be used as a pollutant adsorbent to repair

Methods

Results

Conclusion