Effective removal of Congo red and hexavalent chromium from aqueous solutions by guar gum/sodium alginate/Mg/Al-layered double hydroxide composite microspheres.

In this paper, Mg/Al-layered double hydroxide (Mg/Al-LDH) was modified with the natural polymers sodium alginate and guar gum, and the prepared GG/SA/Mg-Al-LDH composite microsphere adsorbent (G-LDH) showed better adsorption performance for Congo red and hexavalent chromium in aqueous solution than the Mg/Al-LDH. The adsorption and surface properties of G-LDH in terms of functional groups, basic constituent elements and structural properties were obtained by different techniques. SEM shows that the average particle size of G-LDH is between 400 and 900 nm and exhibits a distinct microsphere morphology. G-LDH showed strong adsorption properties for CR (Congo red) and Cr (VI) solutions with initial concentrations of 80 mg L and 100 mg L, with adsorption amounts of 361.6 mg g and 461.7 mg g. The unique layered structure of Mg/Al-LDH made an indispensable contribution to the efficient adsorption capacity of G-LDH when GG was used to prepare composite microspheres. The adsorption process of G-LDH is consistent with the Langmuir isotherm model and the proposed secondary kinetic model as a heat-absorbing, spontaneous, monolayer, and chemisorption process. G-LDH is an innovative anion adsorbent with excellent adsorption performance at low cost, using natural polymer materials as the backbone and the layered structure of magnesium‑aluminum hydrotalcite as the support.