Tuning of graphene oxide intercalation in magnesium aluminium layered double hydroxide and their immobilization in polyacrylonitrile beads by single step mussel inspired phase inversion: A super adsorbent for lead

Abstract

• Tuning of intercalation of GO in interlayer of MgAl LDH has been demonstrated. • GO intercalated MgAl LDH incorporated polymeric beads are prepared. • Phase inversion in polydopamine restricts leaching of nanoparticles from beads. • Polydopamine modifies bead morphology favoring lead adsorption. • The composite bead exhibits superior selective adsorption for lead (209 mg/g). In the present study, graphene oxide intercalated layered double hydroxide (LDH) based adsorbent was synthesized for effective and selective adsorption of lead. Graphene oxide was intercalated in a controlled manner in the interlayer space of magnesium-aluminium layered double hydroxide which enhanced the adsorption capacity by 20% compared to pristine LDH. Effect of metal ion ratio on GO intercalation was observed. The developed nano-powder was immobilized in polyacrylonitrile beads by a single step mussel inspired phase inversion in dopamine solution. Elongated macro-voids accelerated the lead adsorption kinetics remarkably. Phase inversion in dopamine eliminated the leaching of the nanoparticles from beads. The GO intercalated LDH and the nanoparticles immobilized beads showed lead adsorption capacity of 1062 mg/g and 209 mg/g, respectively, at 323 K and pH 5.8. Adsorption isotherm showed the best fitting with Langmuir model and kinetics followed a pseudo-second order rate equation. Lead adsorption was not affected significantly by the presence of other cations, like, Ca 2+ , Mg 2+ , Fe 2+ and Zn 2+ . The bead was utilized in continuous column study and showed a breakthrough time of 35.5 h with 15 cm bed height and 10 ml/min flow rate. The bead showed good performance with real life lead containing battery effluent. The adsorbents were regenerated using 0.1(M) EDTA and reused for at least five cycles without significant reduction in lead removal efficiency. The findings of the present study suggest that the synthesized adsorbent can be used effectively for sustainable and selective adsorption of lead from real life effluent.