Construction of a novel S-scheme heterojunction piezoelectric photocatalyst V-BiOIO3/FTCN and immobilization with floatability for tetracycline degradation.

A high-performance piezoelectric photocatalyst (V-BiOIO3/FTCN) was constructed to improve removal efficiency of tetracycline hydrochloride (TCH). The role of V-BiOIO3 in the composite was to introduce piezoelectric effect and construct S-scheme heterojunction photocatalyst with fish scale tubular carbon nitride (FTCN). The morphology, structure, chemical composition and optoelectronic characteristics of the as-prepared photocatalysts were studied by SEM, TEM, XRD, XPS and UV-Vis DRS. Combined with UV-Vis DRS, XPS valence band, Mott-schottky curve and theoretical calculations, the mechanism of TCH degradation was deeply analyzed. A series of degradation experiments showed that the V-BiOIO3/FTCN could effectively degrade TCH, and the removal efficiency was further improved under the action of ultrasound. Importantly, the further immobilized V-BiOIO3/FTCN/MS could float on the water surface to degrade TCH without additional stirring, which facilitated the recovery of photocatalysts and showed excellent practical application value. This work provided a reference for the design and immobilization of carbon nitride-based piezoelectric photocatalysts.

Tube wall delamination engineering induces photogenerated carrier separation to achieve photocatalytic performance improvement of tubular g-C3N4.

Morphology adjustment is a feasible method to change the physicochemical properties of photocatalysts. The issue that excessively thick tube wall of tubular g-C3N4 is not conducive to the electron migration from inside to the surface thus inhibiting the separation of photogenerated carriers has always been ignored. Potassium ions were used to regulate the structure of the tubular supramolecular precursor by breaking hydrogen bonds, thereby promoting the synthesis of delaminated laminar tubular g-C3N4 (K-CN), which not only shortened the transfer distance of photogenerated electrons but also provided abundant reaction active sites. Experiments and DFT calculations were combined to reveal the details of the physicochemical properties of K-CN. The photocatalytic capacity of K-CN for tetracycline hydrochloride (TCH) degradation and H2O2 generation were 83% and 133 µM, respectively. This work not only synthesized a novel delaminated tubular g-C3N4 but also provided a strategy and inspiration for structure and performance optimization for tubular g-C3N4.

In-situ self-assembly construction of hollow tubular g-C3N4 isotype heterojunction for enhanced visible-light photocatalysis: Experiments and theories.

A highly reactive hollow tubular g-C3N4 isotype heterojunction (SCN-CN) was designed to enhance visible light absorption and manipulate the directed transfer of electrons and holes. The results of UV-vis DRS, XPS valence band and DFT theoretical calculations indicated S doping increases the visible-light absorption capacity and changed the ba nd gap structure of g-C3N4 (CN), resulting in the transfer of electrons from the CN to the SCN and holes from the SCN to the CN under visible light. In addition, the tubular structure of the SCN-CN facilitated the transfer of electrons in the longitudinal direction, which reduced charge carrier recombination. Furthermore, the optical properties, electronic structure, and electron transfer of SCN-CN were also studied by experiments and theoretical calculations. The antibiotic tetracycline hydrochloride (TCH) and dye Rhodamine B (RHB) were subjected to evaluate the photocatalytic performance of SCN-CN. The scavenger tests and ESR data showed that the h+, ·O2- and ·OH worked together in the photocatalytic process. Moreover, the photocatalytic degradation pathway was analyzed by LC-MS. This study synthesized a hollow tubular CN isotype heterojunction with high visible-light photocatalytic performance and provided a theoretical basis for CN isotype heterojunction.

Magnetic chitosan-hydroxyapatite composite microspheres: Preparation, characterization, and application for the adsorption of phenolic substances.

The phenolic substances in sugarcane juice seriously affect the color value of sugar products, and gallic acid is one of the main phenolic substances. To develop a new adsorbent able to effectively adsorb phenolic substances from sugarcane juice, magnetic chitosan (CS) hydroxyapatite (HA) microspheres (MCHAM) were prepared by growing HA on magnetic CS microspheres (MCM) in-situ. MCHAM could effectively adsorb gallic acid from sucrose solution, and the highest adsorption capacity was 40.77 mg g-1. The adsorption kinetics indicated that the adsorption process fit the pseudo-second-order mode, the dominant mechanism was chemisorption, and the Langmuir isotherm mode (qm = 48.12 mg g-1) described the adsorption behavior of MCHAM best. Recycling experiments indicated that the MCHAM adsorbent presented considerable repeatability. Compared to treating phenolic substances in sugarcane juice using traditional clarifying agents, treatment methods employing MCHAM can efficiently and simply remove phenolic substances without leaving residual sulfur in sugarcane juice.