Effects of mixed enzymolysis alone or combined with acetylation or carboxymethylation on the role of jujube kernel fibre as a biosorbent for wastewater treatment

Abstract

Jujube kernel fibre (JKF) could serve as a renewable, abundant, low-cost, and environmentally friendly adsorbent for wastewater if its adsorption capacities are improved. However, data on the modification of JKF, especially on the combination of biological and chemical modifications, are scarce. Therefore, for the first time, we studied the effect of mixed enzymolysis alone or combined with acetylation or carboxymethylation on the structure and adsorption capacities of JKF. After these modifications, the microstructure of JKF became more porous, and its soluble fibre and extractable polyphenol contents, surface area and adsorption capacities for nitrite, copper, and lead ions were all significantly improved (P < 0.05). Meanwhile, mixed enzymatic hydrolysis and acetylation treated JKF showed the highest surface hydrophobicity (43.57) and oil-adsorption ability (4.47 g g⁻¹), while mixed enzymatic hydrolysis and carboxymethylation treated JKF exhibited the highest water adsorption ability (10.66 g g⁻¹), water expansion ability (8.50 mL g⁻¹), and lead and copper ion chelating abilities. Additionally, mixed enzymatic hydrolyzed JKF had the highest nitrite-ion-adsorption ability (10.57 μmol g⁻¹). It can be concluded that mixed enzymolysis combined with carboxymethylation is an optimal way to increase the hydration properties and heavy-metal-adsorption capacity of JKF, while mixed enzymolysis combined with acetylation is an effective approach to enhance the oil-adsorption capacity of JKF.