Biochar typically consists of both carbon and mineral fractions, and the carbon fraction has been generally considered to determine its properties and applications. Recently, an increasing body of research has demonstrated that mineral components inherent in biochar, such as alkali or alkaline earth metals in the form of carbonates, phosphates, or oxides, could also influence the properties and thus the applications. The review articles published thus far have mainly focused on multiple environmental and agronomic applications of biochar, including carbon sequestration, soil improvement, environmental remediation, etc. This review aims to highlight the indispensable role of the mineral fraction of biochar in these different applications, especially in environmental applications. Specifically, it provides a critical review of current research findings related to the mineral composition of biochar and the effect of the mineral fraction on the physicochemical properties, contaminant sorption, carbon retention and stability, and nutrient bioavailability of biochar. Furthermore, the role of minerals in the emerging applications of biochar, as a precursor for fuel cells, supercapacitors, and photoactive components, is also summarized. Overall, inherent minerals should be fully considered while determining the most appropriate application for any given biochar. A thorough understanding of the role of biochar-bound minerals in different applications will also allow the design or selection of the most suitable biochar for specific applications based on the consideration of feedstock composition, production parameters, and post-treatment.
16In this study, the degradation performance of 1,1,1-trichloroethane (TCA) involving both 17 oxidation and reduction processes was investigated with an application of the persulfate-ZVI 18 (zero-valent iron) system, in which it is generally believed that SO4 −• -induced oxidation was 19 responsible for pollutants removal. The study was conducted with persulfate and 20 un-pretreated ZVI through batch experiments. The results showed that TCA was stable in the 21 presence of ZVI alone within 12 h and degraded with the addition of persulfate. TCA 22 degradation efficiency was found to increase with increasing persulfate concentrations, but to 23 decrease with increasing ZVI dosage. A two-stage process involving persulfate oxidation and 24 ZVI reduction was developed during TCA degradation. The addition of isopropanol and 25 tert-butyl alcohol proved the existence of sulfate and hydroxyl radicals during the 1st-stage 26 (0~2 h), which were absent in the 2-nd stage (2~12 h) when persulfate was exhausted. The 27 degradation performance of carbon tetrachloride, a reduction probe compound, was evidence 28 of the persulfate-ZVI system involving an enhanced ZVI reduction, and which was mainly 29 responsible for TCA degradation in the 2nd-stage. 1,1-Dichloroethane was the only 30 confirmed intermediate emerging during the 2nd-stage. 31
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