Egg White-Mediated Fabrication of Mg/Al-LDH-Hard Biochar Composite for Phosphate Adsorption

Phosphorus is one of the main causes of water eutrophication. Hard biochar is considered a promising phosphate adsorbent, but its application is limited by its textural properties and low adsorption capacity. Here, an adhesion approach in a mixed suspension containing egg white is proposed for preparing the hybrid material of Mg/Al-layered double hydroxide (LDH) and almond shell biochar (ASB), named L-A(E) or L-A (with or without egg white). Several techniques, including XRD, SEM/EDS, FTIR and N(2) adsorption/desorption, were used to characterize the structure and adsorption behavior of the modified adsorbents. The filament-like material contained nitrogen elements at a noticed level, indicating that egg white was the crosslinker that mediated the formation of the L-A(E) hybrid material. The L-A(E) had a higher phosphate adsorption rate with a higher equilibrium adsorption capacity than the L-A. The saturation phosphate adsorption capacity of L-A(E) was nearly three times higher than that of L-A. Furthermore, the number of surface groups and the density of the positively charged surface sites follow the ASB < L-A < L-A(E) order, which is consistent with their phosphate adsorption performance. The study may offer an efficient approach to improving hard biochar’s adsorption performance in wastewater treatment.