Simultaneous and efficient removal of Cr(VI) and methyl orange on LDHs decorated porous carbons

Layered double hydroxides (LDHs) are currently attracting intense research interests as pollutant adsorbent due to its low cost, non-toxicity, structure amenability and anion exchange capability. Herein, 3-dimensional (3D) flower-like Ni/Al LDH were prepared to decorate H3PO4 activated biomass-derived porous carbons (PAB) via a facile and green hydrothermal method. The as-synthesized nanocomposites (Ni/Al@PAB) displayed favorable removal performance towards both Cr(VI) and methyl orange (MO) from aqueous solution due to the inherited excellent Cr(VI) removal ability from PAB and MO removal ability from Ni/Al LDH. In single-component removal system, the maximum adsorption capacity of 271.5 and 412.8 mg/g for Cr(VI) and MO were achieved on Ni/Al@PAB, respectively. Remarkably, the removal capacity of Cr(VI) and MO both increased in the Cr(VI)-MO binary system due to the synergistic effect including, (i) additional adsorption sites of N-containing groups from MO, (ii) electrostatic interactions by the reduced Cr(III), and (iii) mutual thermal compensation in the binary system. This work paved the way for designing novel LDHs-decorated porous carbon adsorbents and revealed that the acicular Ni/Al LDH decorated PAB could be applied as efficient and simultaneous adsorbent for coexisting toxic pollutants situations.