Adsorption and thermodynamic mechanisms of manganese removal from aqueous media by biowaste-derived biochars

Abstract

In the present investigation, poultry manure and farmyard manure-derived biochars were applied as cost-effective adsorbents for manganese (Mn) removal from aqueous media. Effects of functional parameters such as solution pH, contact time, temperature and concentration on the Mn removal efficiency of biochars were evaluated. Poultry manure-derived biochar exhibited greater adsorption efficiency than farmyard manure-derived biochar due to its porosity and surface functionality. The maximum adsorption was achieved at pH 6, temperature 298 K and contact time of 3 h. The adsorption isotherm data was well fitted to the Freundlich model indicating multilayer adsorption onto heterogeneous surfaces of the biochars. Thermodynamics calculations affirmed that Mn adsorption onto biochars was spontaneous and exothermic process governed by hydrogen bonding type of electrostatic interaction. Post-adsorption spectroscopic analysis of Mn-loaded biochars evidenced the binding of Mn with active surface functionalities of biochars. (C) 2018 Elsevier B.V. All rights reserved.