https://nova.newcastle.edu.au/vital/access/ /manager/Index en-au 5 https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:37953 VI and As^V from water in mono- and binary-adsorbate systems. The adsorption kinetics and isotherm data for Se^VI and As^V were adequately described by the pseudo-second-order (PSO) (r²>0.94) and Freundlich (r²>0.93) equations. Results from scanning electron microscopy showed that the dimension of the NZVI immobilized on the Mt was smaller than pure NZVI. Using 0.05 g of adsorbent and an initial 200 mg L⁻¹ As^V and Se^VI concentration, the maximum adsorption capacity (q_max and partition coefficient (PC) for As^V on NZVI-Mt in monocomponent system were 54.75 mg g^-1 and 0.065 mg g^-1·μM^-1, which dropped respectively to 49.91 mg g^-1 and 0.055 mg g^-1·μM^-1 under competitive system. For Se^VI adsorption on NZVI-Mt in monocomponent system, q_max and PC were 28.63 mg g^-1 and 0.024 mg g^-1·μM^-1, respectively. Values of q_max and PC were higher for NZVI-Mt than NZVI and montmorillonite, indicating that the nanocomposite contained greater adsorption sites for removing both oxyanions, but with a marked preference for As^V. Future research should evaluate the effect of different operational variables on the removal efficiency of both oxyanions by NZVI-Mt.]]> Wed 06 Dec 2023 09:51:50 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:33010 SO₄ =(mSO₄/mCO₃)_solid/(mSO₄/mCO₃)_solution. High crystal growth rates (driven by either pH or saturation state) encouraged higher values of D_SO₄ because of an increasing concentration of defect sites on crystal surfaces. At low growth rates, D_SO₄ was reduced due to an inferred competition between sulphate and bicarbonate at the calcite surface. These experimental results are applied to understand the incorporation of sulphate into speleothem calcite. The experimentally determined pH-dependence suggests that strong seasonal variations in cave air PCO₂ could account for annual cycles in sulphate concentration observed in stalagmites. Our new experimentally determined values of D_SO₄ were compared with D_SO₄ values calculated from speleothem-drip water monitoring from two caves within the Austrian and Italian Alps. At Obir cave, Austria, D_SO₄ (×10⁵) varies between 11.1 (winter) and 9.0 (summer) and the corresponding figures for Ernesto cave, Italy, are 15.4 (winter) and 14.9 (summer). These values approximate predicted D_SO₄ values based on our chamber experiments containing both low (2 ppm) and high (20 ppm) sulphate concentrations. Our experimental values of D_SO₄ obtained at crystal growth rates typical of stalagmites, closely match those observed in other cave sites from around the world. This validates the universality of the controls behind D_SO₄ and will enhance the use of speleothem CAS as a palaeoenvironmental proxy.]]> Tue 03 Sep 2019 18:19:27 AEST ]]>