https://ogma.newcastle.edu.au/vital/access/ /manager/Index en-au 5 https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:33681 −1. Fluoride removal half-life (t_0.5) values were found to increase in the order Ba ≈ stonedust (a 99% pure natural calcite) < Cd < Co < Mn. A barrier width of 0.97 ± 0.02 m was found to be required for the fluoride/calcite (stonedust) only system when using no factor of safety, whilst in the presence of Mn and Co, the width increased to 2.76 ± 0.28 and 19.83 ± 0.37 m respectively. In comparison, the PSO model predicted a required barrier thickness of ∼46.0, 62.6 & 50.3 m respectively for the fluoride/calcite, Mn and Co systems under the same conditions.]]> Wed 04 Dec 2019 12:54:35 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:28144 2 +, Ba^{2 +} and Mn^{2 +}) on the kinetics of fluoride removal from solution by natural zeolite was investigated. In order to better understand the kinetics, the pseudo-second order (PSO), Hill (Hill 4 and Hill 5) and intra-particle diffusion (IPD) models were applied. Model fitting was compared using the Akaike Information Criterion (AIC) and the Schwarz Bayesian Information Criterion (BIC). The Hill models (Hill 4 and Hill 5) were found to be superior in describing the fluoride removal processes due to the sigmoidal nature of the kinetics. Results indicate that the presence of Mn (100 mg L^{- 1}) and Cd (100 mg L^{- 1}) respectively increases the rate of fluoride sorption by a factor of ~ 28.3 and ~ 10.9, the maximum sorption capacity is increased by ~ 2.2 and ~ 1.7. The presence of Ba (100 mg L^{- 1}) initially inhibited fluoride removal and very poor fits were obtained for all models. Fitting was best described with a biphasic sigmoidal model with the degree of inhibition decreasing with increasing temperature suggesting that at least two processes are involved with fluoride sorption onto natural zeolite in the presence of Ba.]]> Sat 24 Mar 2018 07:36:37 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:27533 Hill 4 > pseudo-second order > Elovich > Power > IPD as given by the evidence ratios, information criterion weights and Bayes factors. The extra sum-of-squares F-test, only applicable to nested models, confirms the best fit order as Hill 5 > Hill 4 > PSO models. Two new parameters (T and k_Hill) have also been defined that give the Hill models a mechanistic meaning directly comparable to the well-defined parameters of the pseudo-second-order model, namely, the pseudo-second-order rate constant k_pso and the instantaneous sorption coefficient h_pso. In the field of geochemistry the use of the four and five parameter Hill models for describing sorption kinetics has been overlooked with many studies favouring the PSO model. It is strongly recommended that the Hill model be considered more widely as a general predictive tool in geochemistry.]]> Sat 24 Mar 2018 07:28:58 AEDT ]]>