Structure investigation of nano-FeO(OH) modified clinoptilolite tuff for antimony removal

Biomimetic sol-gel synthesis was used to prepare new FeO(OH) zeolite (clinoptilolite tuff) adsorbent effective for antimony removal. The product was compared with other on the market accessible natural or commercial adsorption materials like granulated ferric hydroxide GEH, powder of zero valent iron (ZVI)- nanofer and the new synthesized oxi(hydr)oxide FeO(OH) and characterized by XRD, XPS, Raman, FT IR, TG, DTA, DTG, TEM and SEM techniques. Based upon the SEM analysis, the oxidized nanofer sample revealed the existence of hematite and goethite and morphology of FeO(OH) dopant confirmed the presence of ferrihydrite, in less extent also magnetite and hematite. Recorded exothermic maxima on DTA curves for powdered FeO(OH) zeolite at 460 °C and for pure component FeO(OH) at 560 °C indicated an 100 °C shifted exothermic effect, which characterized strong chemical interaction of FeO(OH) with zeolite structure. Based upon the XPS analyses, also the difference between Fe species in the raw and FeO(OH) doped zeolite was found in increasing Si/Al ratio, however only at the surface below app. 5 nm, measured as 3.94 for raw and 5.38 for sample treated with alkalic solution. The plotting of adsorption isotherms in the system studied clearly showed the increasing uptake capacity of the adsorbents towards antimony with the increased S(BET) data (GEH ˃FeO(OH)˃FeO(OH) zeolite˃nanofer)

Batch-wise adsorption, saxs and microscopic studies of zeolite pelletized with biopolymeric alginate

Removal of nitrates, sulfate and Zn(II) ions from aqueous solutions through adsorption onto biopolymeric alginate/clinoptilolite-rich tuff pellets was studied by using an equilibrium batch technique. The idea of this approach of biosorbent fabrication is to promote the native zeolite adsorption performance and thus to prepare more efficient amphoteric tailor-made products for specific environmental targets. A flexible component, i.e., alginate biopolymer, and a rigid component (pulverized) zeolite were crosslinked using Fe(III) and Ca(II) chlorides, additively. The extent of adsorption was found to be considerably higher than with the other mostly natural adsorbents examined towards similar pollutants. The equilibrium adsorption data for the above pollutants were satisfactorily fitted to Freundlich and Langmuir isotherms, respectively. According to the linscale SAXS pattern, there was a strong background visible, which may indicate the presence of a considerable amount of biopolymeric phase in the composite samples analysed. Scanning Tunneling, Electron and Atomic Force Microscopies helped visualize their surface texture and morphology