https://ogma.newcastle.edu.au/vital/access/ /manager/Index en-au 5 https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:22765 Wed 11 Apr 2018 12:10:12 AEST ]]> 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:53602 Mon 29 Jan 2024 18:21:32 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:40443 2) due to their low cost and abundant availability in many regions around the world. However, the performance of these materials is quite limited because of their small pore size and restricted specific surface area. In this work, we report on the physicochemical modification (calcination and dealumination) of natural Indonesian calcite-rich mordenite-clinoptilolite zeolites by acid and high temperature calcination treatment to enhance their CO₂ adsorption capacity. We demonstrated that the specific surface area of the original material can be finely tuned via simple adjustment of the concentration of HCl. Amongst different preparations, the zeolites treated with the 12 M HCl and calcination at 400 °C registered the highest specific surface area of 179.44 m²/g. This modification resulted in the highest CO₂ adsorption capacity of 5.2 mmol/g at 0 °C and 30 bar, corresponding to specific surface area normalized CO₂ adsorption capacity of 2.91 x 10^-2 mmol/m². This promising result revealed that careful modification of low-cost natural zeolite via a simple phisicochemical treatment not only enhanced the specific surface area and the pore size but also led to excellent CO₂ adsorption affinity when compared with the more costly synthetic materials. This finding demonstrates the potential of low cost natural product to be developed and utilized as a cost-effective adsorbent for CO₂.]]> Fri 22 Jul 2022 14:37:22 AEST ]]>