Tea waste-supported hydrated manganese dioxide (HMO) for enhanced removal of typical toxic metal ions from water. Issue 108 (20th October 2015)

• Record Type: Journal Article
• Authors: Wan, Shunli; Qu, Nan; He, Feng; Wang, Mengkun; Liu, Guobin; He, Hai
• Is Part Of: RSC advances. Volume 5:Issue 108(2015)
• Page Start: 88900
• Page End: 88907
• Publication Date: 2015-10-20
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/c5ra16556c
• Languages: English
• ISSNs: 2046-2069

Abstract

Abstract : A novel composite sorbent with hydrated manganese oxide (HMO) (<5 nm) highly dispersed on tea waste (TW), enjoying synergistic benefits from both materials, efficiently and selectively sorbed Pb(ii ), Cd(ii ), Cu(ii ) and Zn(ii ) from water. Abstract : Tea waste (TW) was modified by depositing hydrated manganese oxide (HMO) onto it through in situ precipitation and a novel hybrid bio-adsorbent, namely HMO-TW, was obtained. The successful deposition of HMO in/on tea waste was confirmed by transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FT-IR) analysis. The removal of four typical heavy metals ( i.e., Pb(ii ), Cd(ii ), Cu(ii ), Zn(ii )) by HMO-TW was pH-dependent, and higher pH favored the sorption at the tested pHs of 2–7. HMO-TW showed excellent sorption selectivity toward all four metal ions, and the removal efficiency of target metal ions was sustained at 30%–90% even in the presence of 50 times higher competing Ca(ii ) and Mg(ii ) ions. Sorption isotherms of four metal ions by HMO-TW are all well represented by the Freundlich model, and the maximum experimental sorption capacities of Pb(ii ), Cd(ii ), Cu(ii ), Zn(ii ) were 174.3, 78.38, 54.38 and 37.5 mg g −1, respectively. Compared to the unmodified tea waste, the sorption capacities and selectivity of Pb(ii ), Cd(ii ) and Cu(ii ) onto HMO-TW improved significantly. The sorption process reached equilibrium within 200 min, and the kinetics could be well fitted by a pseudo-second order model. Fixed-bed column sorption results further showed that the bed volume (BV) of C e / C 0 reaching 0.5 for Pb(ii ), Cd(ii ), Cu(ii ), Zn(ii ) were 1170, 1130, 820 and 1450 BV, respectively. In addition, the exhausted HMO-TW can be effectively regenerated using a 0.5 M HCl solution. All results reported herein validate that HMO-TW is a promising sorbent for practical treatment of heavy metal contaminated water.