Facilitative capture of As(V), Pb(II) and methylene blue from aqueous solutions with MgO hybrid sponge-like carbonaceous composite derived from sugarcane leafy trash.

Enhancing the contaminant adsorption capacity is a key factor affecting utilization of carbon-based adsorbents in wastewater treatment and encouraging development of biomass thermo-disposal. In this study, a novel MgO hybrid sponge-like carbonaceous composite (HSC) derived from sugarcane leafy trash was prepared through an integrated adsorption-pyrolysis method. The resulted HSC composite was characterized and employed as adsorbent for the removal of negatively charged arsenate (As(V)), positively charged Pb(II), and the organic pollutant methylene blue (MB) from aqueous solutions in batch experiments. The effects of solution pH, contact time, initial concentration, temperature, and ionic strength on As(V), Pb(II) and MB adsorption were investigated. HSC was composed of nano-size MgO flakes and nanotube-like carbon sponge. Hybridization significantly improved As(V), Pb(II) and methylene blue (MB) adsorption when compared with the material without hybridization. The maximum As(V), Pb(II) and MB adsorption capacities obtained from Langmuir model were 157 mg/g, 103 mg/g and 297 mg/g, respectively. As(V) adsorption onto HSC was best fit by the pseudo-second-order model, and Pb(II) and MB with the intraparticle diffusion model. Increased temperature and ionic strength decreased Pb(II) and MB adsorption onto HSC more than As(V). Further FT-IR, XRD and XPS analysis demonstrated that the removal of As(V) by HSC was mainly dominated by surface deposition of MgHAsO4 and Mg(H2AsO4)2 crystals on the HSC composite, while carbon π-π* transition and carbon π-electron played key roles in Pb(II) and MB adsorption. The interaction of Pb(II) with carbon matrix carboxylate was also evident. Overall, MgO hybridization improves the preparation of the nanotube-like carbon sponge composite and provides a potential agricultual residue-based adsorbent for As(V), Pb(II) and MB removal.