Enhanced recovery of phosphate from wastewater using hollow hierarchical hydrotalcite/hydroxide composite microspheres adsorbent

Abstract

The release of untreated phosphate into water systems is of great environmental concern, thus many adsorption methods have been developed to deal with this issue. In the present paper, we prepared magnesium/aluminum (Mg/Al)-based hydrotalcite/Al(OH)3 adsorbent with a hierarchical structure using a hydrothermal approach. Tests were conducted to assess variation in the Al/Mg mole ratio, interaction time, solution pH, competitive adsorption, and initial concentration of anions on the uptake of phosphate anions. The outcome revealed that 96.8 % of phosphate could be adsorbed within 2 h using the sample with an Al-to-Mg molar ratio of 1:3 (AM-3) with Langmuir theoretical maximum adsorption rate of 94.08 mg-P/g at 25 °C, which is 1.59 and 5.98 times higher than MgO (M) and Al2O3 (M) samples, respectively. The equilibrium experiment outcomes were fitted with the isotherm kinetic models and the results confirmed an adsorption mechanism involving surface adsorption that introduced phosphate ions into the layered structure of composite. The improved phosphate adsorption on AM-3 sample was attributed to the interaction of phosphate and hydroxyl ions during the adsorption. According to our experimental findings, the hydrotalcite prepared offers a great deal of promise for application as an adsorbent for the recovery of phosphate in environmental remediation.