Hydrogen phosphate anions modified hydrogen titanate nanotubes for methylene blue adsorption from aqueous solution: Validating novel method of predicting adsorption capacity

Adsorption and Degradation Kinetics of Methylene Blue on As-prepared and Calcined Titanate Nanotubes

“…The indirect optical band gap energy of the titanate nanotubes was calculated by plotting the function (F(R)hυ) 0.5 vs. E (Tauc plot) and extrapolating the linear part of the curve to F(R) = 0 (Figure 4). The E g value obtained for the as-prepared sample was 3.45 eV, which is in agreement with previous titanate nanotubes investigations (Morgado et al, 2007), although lower values were also reported (Jose et al, 2016;Buchholcz et al, 2017;Sandoval et al, 2017) while the thermally treated sample showed E g value of 3.2eV. As it was shown earlier, heat treatment lead to intralayer dehydration of nanotubes which, according to literature (Zhang et al, 2004), cause the formation of oxygen and hydrogen vacancies thus inducing defect states and reducing the bandgap of titanate nanotubes (Sun et al, 2015).…”

“…The BET specific surface area of the as-prepared titanate nanotubes was determined to be 334.87m 2 g -1 . Specific surface area depends greatly on synthesis conditions and post-treatment but similar values for specific surface areas of titanate nanotubes are reported (Jose et al, 2016;Buchholcz et al, 2017;Sandoval et al, 2017;Subramaniam et al, 2017), while nanotubes thermally treated at 250°C for 2h showed specific surface area of 301.80m 2 g -1 . The drop in surface area after calcination is a consequence of partial transformation to anatase (Morgado et al, 2006).…”

“…The adsorption equilibrium capacities are 47 and 93mg g -1 for as-prepared and calcined sample, respectively. Comparison with literature results is not straight forward since various nanotubes types were used and adsorption conditions utilized, for example Jose et al (2016) reported MB adsorption capacity of hydrogen phosphate modified titanate nanotubes of 139mg g -1 for initial concentration of MB of 0.25mmol L -1 . Obtained total adsorption capacities are quite high and are the consequence of good affinity between dye molecules in cationic form and titanate nanotubes with anionic character surface (Bavykin et al, 2010).…”

“…It is possible that the calcined sample possesses a greater number of active sites for the dye molecules adsorption. The adsorption kinetics data was fitted to pseudo-second-order model since previous investigations (Xiong et al, 2010;Hu et al, 2011;Jose et al, 2016) showed that this model describes well the adsorption kinetics of methylene blue onto titanate nanotubes. The pseudo-second-order model can be expressed by the following linear form (Xiong et al, 2010):…”

Functionalized Cellulose for the Controlled Synthesis of Novel Carbon–Ti Nanocomposites: Physicochemical and Photocatalytic Properties

“…The fast adsorption processes of the CPTi2 composite could be favored by chemical interactions of the carbon surface with the dye in solution. The beneficial effect on the dye adsorption of phosphate doping in Ti structures was previously reported [29,54] as due to the modification of the electrostatic interactions. Nevertheless, the best final performance of CNTi samples confirms the importance of a developed porosity in the interactions with the pollutant.…”