Enhanced lead and cadmium removal using biochar-supported hydrated manganese oxide (HMO) nanoparticles: Behavior and mechanism

• Published in: The Science of the total environment 2018-03, Vol.616-617, p.1298-1306
• Main Authors: Wan, Shunli, Wu, Jiayu, Zhou, Shanshan, Wang, Rui, Gao, Bin, He, Feng
• Format: Article
• Language: English
• Subjects: Adsorption; Biochar; Heavy metal; Hydrated manganese oxides; Selectivity
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2017.10.188

Hydrated manganese oxide (HMO) nanoparticles were impregnated into a peanut shell-derived biochar (BC) to obtain a remarkable nanocomposite adsorbent, HMO-BC, which overcomes the technical barriers of singly applying either HMO or BC in practical heavy metal-containing wastewater treatment. HMO-BC can effectively sequestrate Pb(II) and Cd(II) in a wide pH range of 3–7 and exhibited more preferable sorption than bare BC in the presence of high-level competing cations. BC also significantly lowered the Mn leaching at acidic pH. Fixed-bed column adsorption tests showed that the effective treatment volume of HMO-BC for a simulated Pb(II)- or Cd(II)-laden wastewater is about 4–6 times higher than that of the BC host. In addition, HMO-BC was effective in removing Pb(II) from a real Pb-containing electroplating wastewater to discharge limit (0.2mgL−1) with treatable volume of 525BV, much higher than that of the bare BC (60BV). More importantly, the saturated HMO-BC can be thoroughly regenerated for repeated uses without any observable capacity loss. Such attractive results of HMO-BC were attributed to the complementary effect of its two components. The embedded HMO nanoparticles provide preferable capture of target cations through specific inner-sphere complexation, as illustrated by XPS spectra of Pb 4f7/2 and O1s, while the non-diffusive negatively charged oxygen-containing groups bound to BC facilitate the pre-enrichment and permeation of Pb(II) and Cd(II) cations into the pore channels prior to their preferable sorption through the Donnan membrane effect. [Display omitted] •HMO-BC was fabricated for real wastewater treatment in column settings.•HMO endows HMO-BC higher sorption selectivity and capacity than bare BC.•BC facilitates the pre-enrichment of Pb(II) and Cd(II) for enhanced sorption.•The exhausted HMO-BC can be thoroughly regenerated for repeated uses.