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1.
J Environ Sci (China) ; 26(2): 307-14, 2014 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-25076522

RESUMO

We fabricated and characterized two hybrid adsorbents originated from hydrated ferric oxides (HFOs) using a polymeric anion exchanger D201 and calcite as host. The resultant adsorbents (denoted as HFO-201 and IOCCS) were employed for Sb(V) removal from water. Increasing solution pH from 3 to 9 apparently weakened Sb(V) removal by both composites, while increasing temperature from 293 to 313 K only improved Sb(V) uptake by IOCCS. HFO-201 exhibited much higher capacity for Sb(V) than for IOCCS in the absence of other anions in solution. Increasing ionic strength from 0.01 to 0.1 mol/L NaNO3 would result in a significant drop of the capacity of HFO-201 in the studied pH ranges; however, negligible effect was observed for IOCCS under similar conditions. Similarly, the competing chloride and sulfate pose more negative effect on Sb(V) adsorption by HFO-201 than by IOCCS, and the presence of silicate greatly decreased their adsorption simultaneously, while calcium ions were found to promote the adsorption of both adsorbents. XPS analysis further demonstrated that preferable Sb(V) adsorption by both hybrids was attributed to the inner sphere complexation of Sb(V) and HFO, and Ca(II) induced adsorption enhancement possibly resulted from the formation of HFO-Ca-Sb complexes. Column adsorption runs proved that Sb(V) in the synthetic water could be effectively removed from 30 microg/L to below 5 microg/L (the drinking water standard regulated by China), and the effective treatable volume of IOCCS was around 6 times as that of HFO-201, implying that HFO coatings onto calcite might be a more effective approach than immobilization inside D201.


Assuntos
Antimônio/isolamento & purificação , Compostos Férricos/química , Adsorção , Resinas de Troca de Ânions/química , Carbonato de Cálcio/química , Concentração de Íons de Hidrogênio , Concentração Osmolar
2.
Environ Sci Technol ; 48(9): 5101-7, 2014 May 06.
Artigo em Inglês | MEDLINE | ID: mdl-24730751

RESUMO

Hydrous manganese oxide (HMO) is generally negatively charged at circumneutral pH and cannot effectively remove anionic pollutants such as phosphate. Here we proposed a new strategy to enhance HMO-mediated phosphate removal by immobilizing nano-HMO within a polystyrene anion exchanger (NS). The resultant nanocomposite HMO@NS exhibited substantially enhanced phosphate removal in the presence of sulfate, chloride, and nitrate at greater levels. This is mainly attributed to the pHpzc shift from 6.2 for the bulky HMO to 10.5 for the capsulated HMO nanoparticles, where HMO nanoparticles are positively charged at neutral pH. The ammonium groups of NS also favor phosphate adsorption through the Donnan effect. Cyclic column adsorption experiment indicated that the fresh HMO@NS could treat 460 bed volumes (BV) of a synthetic influent (from the initial concentration of 2 mg P[PO4(3-)]/L to 0.5 mg P[PO4(3-)]/L), while only 80 BV for NS. After the first time of regeneration by NaOH-NaCl solution, the capacity of HMO@NS was lowered to ∼ 300 BV and then kept constant for the subsequent 5 runs, implying the presence of both the reversible and irreversible adsorption sites of nano-HMO. Additional column adsorption feeding with a real bioeffluent further validated great potential of HMO@NS in advanced wastewater treatment. This study may provide an alternative approach to expand the usability of other metal oxides in water treatment.


Assuntos
Compostos de Manganês/química , Óxidos/química , Fosfatos/isolamento & purificação , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água/métodos , Adsorção , Concentração de Íons de Hidrogênio , Microscopia Eletrônica de Transmissão , Nanopartículas , Espectrofotometria Ultravioleta
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