Biodegradable chelator GLDA intercalated magnesium/aluminum layered double hydroxides for efficient phosphate capture and removal from wastewater

Phosphate removal and recovery from wastewater play a vital role in controlling water eutrophication and facilitating resource recycling. Adsorbents of layered double hydroxides (LDHs) exhibit promising potential in the removal of phosphate; however, the removal efficiency often suffers insufficient as easy aggregation and inevitable loss of LDHs. Herein, a novel N, N-bis (carboxymethyl)-L-glutamic acid intercalated magnesium-aluminum LDH (GLDA@MgAl-LDH) were successfully synthesized. Intercalating with GLDA spawned dual functionality, i.e., the layer spacing expansion elevated the loading of phosphate, while GLDA also acted as additional binding sites toward phosphate. A higher phosphate capture (> 90%) was obtained in pH 5.0-8.0. Phosphate uptake was predominantly observed within the first1h, reaching equilibrium in approximately 4 h. The maximum adsorption capacity of 44.17 mg g(-1) was attained for GLDA@MgAl-LDH at pH 6.70, which are far higher than that of pristine MgAl-LDH. GLDA@MgAl-LDH also had the excellent stability and reusability in five adsorption/desorption experiments. The GLDA@MgAl-LDH demonstrated significant efficacy in treating actual phosphate-containing wastewater in the fixed-bed adsorption column. Spectroscopic analysis, in conjunction with density functional theory, elucidated that GLDA intercalation enhanced the adsorption efficiency of MgAl-LDH. The key mechanisms facilitating phosphate removal included electrostatic attraction, anion and ligand exchange, and surface complexation. The above results highlight that GLDA@MgAl-LDH could serve as a promising and environmentally friendly candidate for phosphate treatment from the real wastewater.