Effects of Wet Oxidation Process on Biochar Surface in Acid and Alkaline Soil Environments.

Qinya Fan,Xiangyun Han,Jinlong Yan,Guixiang Quan,Jianxiong Sun,Sanfei Wang,Jia Wang,Liqiang Cui

doi:10.3390/ma11122362

Abstract

Biochar has been studied for remediation of heavy metal-contaminated soils by many researchers. When in external conditions, biochar in soils ages, which can transform its structural properties and adsorption capacity. This study was conducted with two oxidation processes, HNO3/H2SO4 and NaOH/H2O2, to simulate the effects of biochar in acid and alkaline soil conditions. The results show that the oxygen-containing functional groups increased in aged biochar, which led to improve the ratio of oxygen and carbon (O/C). Nitro functional groups were found in the acid-oxidation treated biochar. Destroyed ditches and scars were observed on the surface of aged biochar and resulted in growth in their specific surface area and porosity. Specific surface area increased by 21.1%, 164.9%, and 63.0% for reed-derived biochar treated with water washing, acid oxidation, and basic oxidation, respectively. Greater peaks in the Fourier Transform Infrared Spectroscopy (FTIR) results were found in C–O and O–H on the surface of field-aged biochar. Meanwhile, mappings of energy-dispersive spectroscopy showed that biochar aged in soil was abundant in minerals such as silicon, iron, aluminum, and magnesium. In summary, biochar subjected to wet oxidation aging had an increased capacity to immobilize Cd compared to unaged biochar, and the adsorption capacity of oxidized biochar increased by 28.4% and 13.15% compared to unaged biochar due to improvements in porosity and an increase in functional groups.

Highlights

With the pursuit of eco-friendly materials, people have shown great interest in biochar in recent years
The results showed that co-composted biochar had a higher cation exchange capacity (CEC), pH, electrical conductance (EC), and nitrogen-loading capacity than uncomposted biochar
Higher N values have been obtained by both techniques, XPS and elemental analysis, for the biochar that were oxidized with HNO3 /H2 SO4, probably due to the generation of N

Summary

Introduction

With the pursuit of eco-friendly materials, people have shown great interest in biochar in recent years. Biochar is the product of oxygen-limited biomass pyrolyzed treatment [1,2]. Many studies have focused on biochar for soil remediation because of its specific physicochemical properties, such as complicated pore structure and the abundance of functional groups on its surface. Biochar meets the requirements of being a relatively inexpensive material in soil remediation [3,4,5,6,7]. 96% and the water-holding capacity by 11%. Water-holding capacity is the most important factor in sandy soil remediation. Cui et al [9] conducted an adsorption experiment (involving cadmium and lead) with peanut hull-derived biochar and found that the adsorbed cadmium (Cd2+ ) and lead (Pb2+ )

Methods

Results

Conclusion