Improved accuracy in multicomponent surface complexation models using surface-sensitive analytical techniques: Adsorption of arsenic onto a TiO2/Fe2O3 multifunctional sorbent

Parasitic Light Absorption, Rate Laws and Heterojunctions in the Photocatalytic Oxidation of Arsenic(III) Using Composite TiO2/Fe2O3

“…We therefore also constructed a rate law where only adsorbed As(V) decreases the reaction rate. The concentration of adsorbed As(V) was estimated using a surface complexation model (SCM) developed in our previous work [45] . This model predicts adsorption as a function of pH and ionic strength, and crucially incorporates competitive adsorption, for example As(V) versus As(III).…”

“…This scattering is not present in the other samples and indicates that larger particles are present in the Fe 2 O 3 sample [55] in agreement with SEM and DLS analysis. [45] The bandgaps of meso-TiO 2 , meso-TiO 2 /Fe 2 O 3 and Fe 2 O 3 powder samples were estimated using a Tauc plot. [56] As absorption could not be determined from the dry powders, F(R), a parameter that is proportional to the extinction coefficient, was determined from diffuse reflectance data using the Kubelka-Munk function.…”

“…[28,[42][43][44] We previously developed new adsorption models for TiO 2 / Fe 2 O 3 composites, showing how the monolayer adsorption of As(V) onto TiO 2 /Fe 2 O 3 obeys component additivity, i. e. the reaction proceeds as adsorption onto non-interacting TiO 2 and Fe 2 O 3 surface components, unaffected when TiO 2 and Fe 2 O 3 are coupled into a composite structure. [45] In contrast, As(III) adsorption is not component additive when there are differences between the morphology of (i) the TiO 2 /Fe 2 O 3 composite and (ii) the single-component TiO 2 and Fe 2 O 3 reference samples, since surface morphology influences the extent of multilayer As(III) adsorption. We also developed a kinetic adsorption model to explore how a treatment based upon simultaneous photocatalytic oxidation-adsorption using TiO 2 /Fe 2 O 3 would be best designed, finding that high concentrations of the media (compared with photocatalysis-only reactors) are required to achieve sufficient sorbent lifetimes.…”

“…We previously developed new adsorption models for TiO 2 /Fe 2 O 3 composites, showing how the monolayer adsorption of As(V) onto TiO 2 /Fe 2 O 3 obeys component additivity, i. e. the reaction proceeds as adsorption onto non‐interacting TiO 2 and Fe 2 O 3 surface components, unaffected when TiO 2 and Fe 2 O 3 are coupled into a composite structure [45] . In contrast, As(III) adsorption is not component additive when there are differences between the morphology of (i) the TiO 2 /Fe 2 O 3 composite and (ii) the single‐component TiO 2 and Fe 2 O 3 reference samples, since surface morphology influences the extent of multilayer As(III) adsorption.…”

“…We first synthesized and characterized TiO 2 and TiO 2 /Fe 2 O 3 photocatalysts, using the synthesis procedure described by Zhou et al [28] . without further optimization, as an example of the typical TiO 2 /Fe 2 O 3 composites prepared by precipitation to produce discrete TiO 2 and Fe 2 O 3 phases [20,22,38,42,45,46] . Previous studies of TiO 2 /Fe 2 O 3 composites have only considered arsenic removal at high As concentrations and/or in blank media [19–21,28,45] .…”