Preparation of layered double hydroxide intercalated by Gallic acid for boron adsorption

Recently, water pollution has become very serious especially with trace amounts of boron in solution. In this work, Layered double hydroxide intercalated by Gallic acid (GA-LDH), a prospective candidate material for borate acid adsorption, was synthesized for the first time by direct precipitation method using Gallic acid (GA), magnesium nitrate, and aluminum nitrate as raw materials. The effects of pH, reaction time, initial concentration of boric acid, coexisting ions and other factors on the adsorption capacity of GA-LDH for B were analyzed. The GA-LDH adsorption capacity of 10 mg·g−1 was reached via the optimized synthesis conditions. And most importantly, compared to conventional NO3-LDH, the adsorption of GA-LDH on B is less disturbed by other ions. The study on the adsorption mechanism revealed that GA-LDH adsorbed boron by complex reaction between the hydroxyls of GA and B(OH)3 or B(OH)4− in solution. Adsorption kinetics thermodynamics and indicated the relationship between the equilibrium concentration of B in the solution and the B adsorption capacity at various temperatures followed the Langmuir model and the reaction rate of B was mainly controlled by the chemisorption mechanism. The elution efficiency could reach 75% by using nitric acid as an eluent.