https://nova.newcastle.edu.au/vital/access/ /manager/Index ${session.getAttribute("locale")} 5 https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:33682 2+ and Cd²⁺ on defluoridation by calcite because Spent Pot Lining (SPL, a byproduct generated during the aluminum production) leachate is a complex chemical cocktail. To better understand defluoridation processes and replicate the situation in the field, column tests were conducted. Results indicate that presence of neither Ba²⁺ nor Cd²⁺ has significant impact on fluoride retention when compared with the blank (no metals) because the relative concentration values (F/F_o) as well as the transport parameters like retardation factor (R_c) and distribution coefficient (K_d) are almost the same. PHREEQC, a geochemical software, was then applied to simulate the column test processes (i.e., 1D reactive/transport processes) based on the mechanism of CaF₂ precipitation followed after calcium dissolution. As indicated in the batch reactor test, addition of Cd²⁺ may inhibit calcite dissolution; therefore, a new phase "CalciteSupp" (a phase representing the suppressed solubility of calcite) was defined. Modeling results exhibit good predictions of observed data, and the log_k solubility of the hypothetical "CalciteSupp" equilibrium phase implies the suppression of calcite dissolution in the metal samples. Moreover, saturation indices obtained by modeling indicate the precipitation of CdCO₃ and BaCO₃, revealing that addition of metals may influence fluoride removal at some point during the process, but has no big impact on overall defluoridation. The initial development of the PHREEQC geochemical model presented shows potential in being able to be used as a predictive tool for the design of fluoride remediation strategies, such as permeable reactive barriers, and transport parameters obtained on the basis of the column tests, and CXTFIT (a computer program for evaluating and estimating transport parameters) modeling can be applied in practical design.]]> Wed 05 Dec 2018 12:10:50 AEDT ]]> https://nova.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://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:42691 Cannabis sativa L.) were found to be far superior for PFAS removal than the next best protein, soy. The use of hemp plant proteins as a possible pump-and-treat solution to PFAS remediation from groundwater has been successfully demonstrated with very good removals (>98%) of the main contaminants of PFOS and PFHxS in approximately 1 h of contact time, with salinity enhancing removal of short chain PFAS. Changes to the secondary structure of hemp proteins was found using FTIR spectroscopy analysis and calculated based on the integrated areas of the amide I component bands. The amount of β-turns increased from ∼9.3% (control) to 44.1% (undiluted groundwater); with a decrease in random coils (25.6–8.6%); α-helix (19.3–8.6%) and β-sheets (38.8–23.1%). These changes indicate that hemp proteins partially unfold during the reaction with PFAS with other FTIR evidence suggesting sorption at hydrophobic sites of the protein as well as with the side chains of the amino acids aspartic and glutamic acid. The absence of these side chains in soy protein, as evidenced from FTIR and amino acid analysis, being part of the reason why soy removed less (approx. half) of the Σ(PFHxS + PFOS) load when compared to hemp. The findings reported here will lead to new, environmentally friendly methods for PFAS remediation.]]> Thu 01 Sep 2022 09:43:23 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:7720 Sat 24 Mar 2018 08:41:39 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:1683 7.5) are not equipped to describe this complex system, largely because the PHREEQ model includes only precipitation reactions, whereas a combination of adsorption and precipitation parameters are required.]]> Sat 24 Mar 2018 08:27:22 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:10731 Sat 24 Mar 2018 08:09:48 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:16839 (g) to CO₂_(aq) could not keep up with the consumption of CO₂_(aq), resulting in an initial disequilibrium with experimental pH reaching equilibrium quickly, while fluoride removal lagged. Increasing stirring rate significantly decreased the extent of disequilibrium and the time at which the CaCO₃ -fluoride-CO₂ system attained equilibrium due to the increased rate of transport of dissolved CO₂ to the CaCO₃ surface, and simultaneously the rate of transport of the dissolved CaCO₃ to the bulk solution. Optimal fluoride removal occurs at pCO₂ ~10-0.52 [30% (mol% CO₂)] with 96% of the initial 2,000 mg/L fluoride load removed in less than 80 min with a stirring rate of 300 revolutions per minute. Increasing pCO₂ to ~100 (100% CO₂) resulted in very little gain, less than 2%, in fluoride removal, or in the time required to reach equilibrium and therefore significant remediation cost savings can be obtained by using pCO₂ 30% when compared to 100%.]]> Sat 24 Mar 2018 07:53:28 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:5198 Sat 24 Mar 2018 07:47:47 AEDT ]]> https://nova.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://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:22725 Hill 4 > PSO due to the ability of the Hill models to accommodate sigmoidal kinetics. Removal of fluoride from SPLL under atmospheric CO2 conditions was found to be inhibited with no removal occurring for the first 3000 min with the inhibition times, based on the reaction half-life, reducing with increased CO₂ partial pressure and stirring rate. X-ray diffraction (XRD) analysis revealed that the residual solid filtrate consisted of trona (Na₃(CO₃)(HCO₃)·2H₂O) a potentially valuable mineral kogarkoite (Na₃SO₄F) and fluorite (CaF₂) accounting for fluoride removal, and unreacted calcite (CaCO₃).]]> Sat 24 Mar 2018 07:15:27 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:54975 Mon 25 Mar 2024 15:21:41 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:45427 Fri 28 Oct 2022 11:48:22 AEDT ]]>