Synthesis and adsorption characteristics of hollow spherical allophane nano-particles

Removal of barium, cobalt, strontium and zinc from solution by natural and synthetic allophane adsorbents

“…Furthermore, one can see that 5-10 min is enough to achieve adsorption equilibrium under the experimental conditions used in this study, which indicates that physical adsorption rather than ion exchange contributes mainly to the removal of metal ions by natural and synthetic allophane adsorbents. This finding is in line with previous experimental results, where allophane has been successfully used in the remediation of aqueous solutions that were contaminated with, for example, heavy metals cations [15,22,33,35], metal (oxy)anions [18,23,30], heterocyclic organic components [10] and anionic surfactants and organic acids [17,23]. …”

“…These values are in the range of N2-BET values previously reported for natural allophanes (~200-400 m²/g) and synthetic allophanes (~250-900 m²/g) [10,29,33]. Noteworthy, the BET values obtained before and after the adsorption experiments were identical to within the analytical precision of the BET analyses, which indicates that changes in the surface area and surface properties of the adsorbents are negligible throughout the experiments.…”

“…In a third set of experiments, the effect of metal ion concentration on the adsorption behavior of allophanes was investigated at pH 8.5 ± 0.1 for 2 h using 0.1 g of the adsorbent and 50 mL of solution containing Ba, Co, Sr and Zn in different concentrations (1,10,20,50 and 100 mg/L). The suspensions were prepared in analogy to those from the second set of experiments.…”

“…≡Al-OH° and ≡Si-OH°) in adsorbents are favorable to ensure a desired adsorption rate and appropriate metal ion removal efficiency [10,11]. Recently, agricultural and industrial waste products, activated carbon nanotubes, cellulose, carbonates, Feand Al-oxyhydroxides, zeolites, phosphates and clay minerals are used in the remediation of water that is severely polluted with persistent and hazardous components such as heavy metal ions, dyes, antibiotics, biocide compounds and other organic chemicals [12][13][14][15][16].…”

Characterization of Allophane from Gamalama Volcanic Soil, North Maluku, Indonesia

“…Si/Al ratio of allophane of Gamalama volcanic soil is 1.45 and from EDX spectra contain impurities 9.53 % Fe (image not shown). Iyoda et al [5] have found same result that the natural allophane from New Zealand also contain impurities such as Fe-minerals containing.…”