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Surface structures of nanoparticles (NPs) designed at the atomic level are vital to enhance the catalytic performance and stability of NPs. In this work, we report the engineering of plate-like and platelet-like BiVO4 NPs for the formation of heterojunctions with Bi2O3. The morphology and size of NPs were observed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Raman spectroscopy, SAED and powder X-ray diffraction (XRD) were carried out to show the structural composition and they confirmed monoclinic phases for both BiVO4 and Bi2O3. BiVO4 NPs notoriously have low surface area and pore volume, thus HPEI was incorporated to improve these properties. Brunuer–Emmett–Teller (BET) technique was used to characterize the surface area (SBET) of the photocatalysts and SBET was increased by 88% after the addition of 0.15 mM HPEI during synthesis. Diffuse reflectance spectroscopy was used to elucidate the optical properties of NPs and a blueshift in the heterojunctions was observed due to the incorporation of Bi2O3. Tuning of {010} monoclinic BiVO4 was achieved after the addition of 0.5 M NaCl which resulted in plate-like morphologies showing improved optical and electronic properties. Uniform platelet-like BiVO4 NPs were synthesized successfully after the addition of 0.15 mM HPEI, and this also induced impaired dispersion and size reduction. The calculated band positions of BiVO4 and Bi2O3 in the heterojunctions were well positioned for carrier charge separation, which was confirmed by the flat band potentials that were 0.553, − 0.47, − 0.70 and − 0.77 V for Bi2O3, p-BiVO4, 0.15HPEI–0.5NaCl–BiVO4–Bi2O3 and 0.5NaCl–BiVO4. [ABSTRACT FROM AUTHOR]

• Novel multiregional DOM with anisotropic scattering developed for OpenFOAM. • Successful validation vs analytical solution and verification vs standard DOM. • Quadrature rotation reduces significantly the directional error in parallel beams. • Power cosine or cone shaped adjusted quadrature for improved simulation of LED. This work describes adaptive quadrature, a new feature designed to improve the Discrete Ordinate Method (DOM) in parallel and cone-shaped radiation sources. OpenFOAM was chosen as the simulation framework to implement the new feature. It already included a Discrete Ordinate Method (fvDOM), but it focuses on thermal radiation and is limited to isotropic emission, diffuse phenomena, and non-scattering media. The model was completed to cover volumetric and superficial absorption, isotropic and anisotropic scattering (with user-defined phase functions), diffuse and specular reflection, diffuse and parallel transmission, and three types of superficial emission sources, i.e., isotropic, cone-shaped, and parallel. Additionally, the model is prepared to work in grey mode or with wavelength bands. Multiple regions with different optical properties are also allowed. Most of the model has been validated by individual simulations of every feature in simple geometries that permit an analytical solution, with errors between 0% and 6.08%. These simulations were also verified in a comparison with an established version of the standard DOM, with differences between model implementations below 2.5%. Some advantages of the developed adaptive quadrature are also analysed using simulation results for different radiative sources and angular discretization. The main conclusion is that adaptive quadrature better defines view angle and light direction of emission sources compared to the established DOM, improving significantly the accuracy of the simulation of non-isotropic sources. [ABSTRACT FROM AUTHOR]

• Mechanistic modelling of E. coli inactivation by photo-Fenton at circumneutral pH. • Radiation transport considering optical properties of iron hydroxide precipitates. • Reversible serial n-event kinetic model successfully describes solar inactivation. • Photo-Fenton cycle mediated by precipitated iron reproduces photosaturation effect. • Multiple target – multiple hit model reproduces synergy of photons and radicals. This work focuses, for the first time, on the mechanistic modelling of wastewater disinfection by the solar photo-Fenton process using controlled solar simulated radiation. At circumneutral pH, iron precipitates forming hydroxides and significantly affecting the optical properties of the water. In this regard, radiation transfer in the reactor has been taken into account. The proposed model considers that the solar inactivation of bacteria follows a serial n-event mechanism with n reversible steps of photonic attacks leading to the bacterial inactivation. Dark Fenton cyclic process of hydroxyl radical formation from hydrogen peroxide is considered to be mediated mainly by precipitated iron species, prevailing at circumneutral pH. Finally, the photo-Fenton process was modelled using a multiple target – multiple hit mechanistic approach that accounts for the synergistic effect between the photonic and the hydroxyl radical attacks to the bacteria. Model predictions successfully reproduce experimental data of solar disinfection, hydrogen peroxide consumption, and photo-Fenton disinfection at circumneutral pH. [ABSTRACT FROM AUTHOR]