Recent Advance on Torrefaction Valorization and Application of Biochar from Agricultural Waste for Soil Remediation

Abstract

With the increase of global proportion of soil pollution and the number of areas at risk, researchers have sought to develop various pathways to repair or relieve the pollutants in soil. Among them, biochar represents one multidimensional soil amendment which has got great deal of attention on its physicochemical properties towards the removal or mitigation of contaminants in soil. A variety of agricultural wastes like straw and manure prepared from different torrefaction process have been employed as feedstock for the production of biochar, which can be applied to the contaminated soil to facilitate the growing environment for crops, and to improve soil fertility and microbial environment. In addition, the utilization of biochar for soil remediation is also considered as a process of carbon sequestration. The purpose of this review is to summarize the latest research progress in torrefaction processes and mechanism of agricultural waste, the effects of different torrefaction methods on the formation and properties of biochar were explained, coupled with the effects of process parameters. Especially, the conversion and mechanisms of biochar prepared from agricultural wastes composed mainly with lignocellulosic material were discussed, and the characteristics of biochar prepared for improving soil physical and chemical characteristics, microbial community characteristics, nutrients, and the stability and relief of soil pollutants, especially heavy metals, are compared. Finally, this work discussed the application and future technical challenges of soil remediation based on agricultural waste derived biochar.

Removal of Nitrate and Phosphate by Starch and Lanthanum Modified Montmorillonite

“…The removal of phosphate can rely on electrostatic adsorption between systems and complexation by ligand exchange, but most studies have shown that the removal of NO3relies on redox reactions. For example, Su Kai et al [32] found that structural ferrous iron on the surface of modified montmorillonite removes NO3from water by a redox reaction with nitrate. In the system studied in this paper, only lanthanum has the ability to redox, and Na is slightly more metallic than La, La does not have the ability to replace Na + from the Na + -NO3system, so there are no conditions for redox reactions, so the adsorption process of NO3by the materials prepared in this paper mainly relies on the electrostatic gravitational force provided by La 3+ and St for the system.…”