Abstract
A promising adsorbent (BBC) was prepared by coating okra (Abelmoschus esculentus L.) mucilage on biochar (BC) surfaces and used to remove methylene blue (MB) from water. Scanning electron microscopic and spectroscopic investigations of BBC indicated the formation of polymeric layer on the biochar surfaces. Point-of-zero-charge (pHpzc) of BC and BBC were observed at pH 4.80 and 7.95 respectively. Adsorption behaviours of Ca2+, Mg2+ and Cr2O72− on biochars also supported pHpzc results. The best condition for MB adsorptions on both biochars was adsorbent dose 1 g·L−1, pH around 8.1, and initial MB concentration 100 mg·L−1. Adsorption of MB on both biochar could be described by Langmuir isotherm and pseudo-second order kinetic models. Langmuir lead adsorption capacities of BC and BBC were 27.47 mg·g−1 and 78.13 mg·g−1, respectively. Results also indicated that MB adsorption on BC was primarily a physisorption process whereas the MB adsorption on BBC was a chemisorption process.
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