Influence of protein internal stability on its removal mechanism from aqueous solutions using eco-friendly horsetail herb-based engineered biochar

Abstract The aim of the study is the determination of adsorption mechanism of two proteins characterized by different internal stability (ovalbumin – OVA, lysozyme – LSZ) on the surface of horsetail herb-based engineered biochar (AC) as well as aggregation degree of the selected solid in the presence of biopolymer in the wide pH range (3-11). The engineered biochar was characterized based on the results of nitrogen adsorption/desorption isotherm method, Boehm titration and elemental compound analysis. The adsorption/aggregation mechanisms were determined using spectrophotometric adsorbed amount measurements, zeta potential, potentiometric titration, turbidity measurements and CPS analyses. Mesoporous horsetail herb-based engineered biochar shows the highest adsorption capacity related to OVA and LSZ at protein isoelectric point (i.e. pH 5 for OVA, pH 11 for LSZ). The OVA and LSZ adsorbed amounts is 395.4 and 493.7 mg/g, respectively. Under the same conditions, the OVA and LSZ presence stimulates the AC particle aggregation. As a result, at selected pH values large protein amounts can easily be removed from the aqueous solution using eco-friendly carbonaceous adsorbent.