Arsenic removal by pomelo peel biochar coated with iron

Abstract

Arsenic present in drinking water is a serious concern due to its high toxicity. In this study, pomelo peel biochar coated with iron (PPCI) through slow pyrolysis carbonization and iron-coating processes was investigated for its ability to remove arsenite As(III) and arsenate As(V). The maximum adsorption capacity of As(III) and As(V) on PPCI at pH = 7 determined by the Langmuir model was11.77 mg/g and 15.28 mg/g, respectively. The PPCI’s adsorption capacity was much higher than that of raw pomelo peel (PP) (0.033 mg/g and 0.034 mg/g for As(III) and As(V), respectively) and many other biomass-derived adsorbents reported in the literature. The change of solution pH (2.0–10 range) did not significantly affect the PPCI’s adsorption capacity to As(III) or As(V) ions. In contrast, the presence of co-existing anions caused differential reductions in As removal efficiency (the effecting order: Cl–<SO42–<CO32–<SiO32–<HPO42–). The characterization of PPCI (morphological, textural, surface functionality, and surface charge properties) before and after adsorption was conducted. Results showed that adsorption mechanisms were reaction between Fe and As in the PPCI’s surface, inner-sphere complexation for As(V) and As(III) ), and electrostatic attraction for As(V). PPCI is simply synthesized from abundant pomelo waste products and can be used for efficiently removing the two forms of toxic As ions from water.