Study on the Adsorption Behavior of Co(II), Pb(II) on Modified Sodium Trititanate Whisker and Its Application to Wastewater
The modification of sodium trititanate whisker surface was performed by means of impregnation procedure to fabricate the modified sodium trititanate whisker, which was characterized by scanning electron microscopy(SEM) and infrared spectroscopy(IR). Its adsorptive performance for Co(II), Pb(II) in a static system was investigated by inductively coupled plasma atomic emission spectrometry(ICP-AES). The main factors affecting adsorption and desorption of Co(II), Pb(II), the adsorptive capacity of Co(II), Pb(II) in optimal condition and adsorption isotherm and the influence of coexistent ions were examined. The comparative test for selectivity was done. The adsorptive rate for Co(II) and Pb(II) on 0.2500 g of modified sodium trititanate whisker at PH 5.0 was the best. Co(II), Pb(II) adsorbed on the modified sodium tretitanate whisker could be eluted with 10 mL of 3.0 mol/L HCl. The adsorptive performance of modified sodium trititanate whisker was better than that of unmodified sodium trititanate whisker. The sobent has been applied to the enrichment and separation of Co(II), Pb(II) in water sample to determine Co(II), Pb(II).
The influence of temperature on the structural behaviour of sodium tri- and hexa-titanates and their protonated forms
Abstract The thermal stability of Na 2 Ti 3 O 7 and Na 2 Ti 6 O 13 , together with that of their protonated forms was investigated. The influence of temperature on the structural behaviour of tri- and hexa-titanates was studied using DTG, XRD, FTIR and FT-Raman. These results were correlated with the nature of the exchangeable cations using elemental analysis and N 2 -sorption. The tunnel structure of Na 2 Ti 6 O 13 revealed a higher thermal stability compared to the layered structure of Na 2 Ti 3 O 7 that shows traces of dimerisation above 800 °C. The sodium forms were observed to be more thermally stable compared to their protonated forms. However, analysis show that ‘H 2 Ti 6 O 13 ’ is much more thermally stable than the layered H 2 Ti 3 O 7 which go through structural changes above 250 °C and suffer a complete structural collapse into anatase/rutile above 800 °C. It was obvious that thermal stability was significantly influenced by the nature of the exchangeable cations and the degree of ion-exchange.
Speci fi cation Test for Panel Data Models with Interactive Fixed E ff ects ∗
In this paper, we propose a consistent nonparametric test for linearity in a large dimensional panel data model with interactive fixed effects. Both lagged dependent variables and conditional heteroskedasticity of unknown form are allowed in the model. We estimate the model under the null hypothesis of linearity to obtain the restricted residuals which are then used to construct the test statistic. We show that after being appropriately centered and standardized, the test statistic is asymptotically normally distributed under both the null hypothesis and a sequence of Pitman local alternatives by using the concept of conditional strong mixing that was recently introduced by Prakasa Rao (2009). To improve the finite sample performance, we propose a bootstrap procedure to obtain the bootstrap -value. A small set of Monte Carlo simulations illustrates that our test performs well in finite samples. An application to an economic growth panel dataset indicates significant nonlinear relationships between economic growth, initial income level and capital accumulation.