Development of biochar-based green functional materials using organic acids for environmental applications

Abstract

Surface functional groups on biochars are one of the key features which determine biochar properties and their potential applications. In this study, biochars obtained from various feedstocks, such as pinewood, pig manure, and almond shell were functionalized using organic acids, such as acetic acid, citric acid, tartaric acid, oxalic acid, and malic acid. For pinewood biochar, citric and acetic acids were found to be effective and citric acid was more efficient in terms of grafting –COOH groups (40% improvement). Tartaric, oxalic and citric acids were found to be effective based on FTIR data for pig manure biochar, however, the effect of acids were minimal on functionalization. Similarly, citric and oxalic acids were found to be effective for almond shell biochar. Citric acid functionalization increased total acidic functional groups by 23%, 10%, and 26%, respectively for pinewood, pig manure, and almond shell. Citric acid-functionalized biochars showed higher removal of the environmentally relevant concentration (500 μg L⁻¹) of emerging contaminant, diclofenac (DCF). For pinewood biochar, at equilibrium, the diclofenac removal increased from 65 to 80%. For almond shell biochar, under similar conditions, the diclofenac removal efficiency increased from 58 to 84%.