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Considerable efforts have focused on pursuing the efficient removal of antibiotic contaminants by combining adsorbents with photocatalysts. However, the reported adsorbents/photocatalysts still suffer from critical drawbacks including low adsorption rate, low mineralization rate, and complicated preparation procedures, greatly restricting their practical application. In this work, we report a facile method to develop porous TiO 2 /BiOI adsorbent through a one-pot hydrothermal process and subsequently low-temperature calcination (280 °C). Adsorption experiment shows that porous TiO 2 /BiOI realizes almost complete removal (99.4%) of tetracyclines, far beyond the values of BiOI (20.2%) and TiO 2 (71.1%). Notably, one-pot synthesis promotes the mass production of TiO 2 /BiOI without obvious loss in adsorption capacity. More importantly, TiO 2 /BiOI adsorbent can be simply regenerated by complete photodegradation of the adsorbed tetracyclines on TiO 2 /BiOI, and regains above 98% of its adsorption capacity for 10 cycles, successfully overcoming the limitations of environment-unfriendly regeneration conditions, low adsorption capacity, and poor recyclability for most of the reported adsorbents/photocatalysts. Additionally, adsorption mechanism is deduced to be mainly electrostatic attraction, hydrogen bonding, and pore filling according to adsorption performance. Therefore, the design concept we present here provides a new perspective for the development of reactive adsorbents with excellent removal efficiency and recyclability through a facile one-pot synthesis. [Display omitted] • TiO 2 /BiOI reactive adsorbent was prepared by a facile one-pot hydrothermal method. • TiO 2 /BiOI showed excellent removal (>99%) of tetracycline from aqueous solution. • One-pot strategy realized the mass production of TiO 2 /BiOI without obvious loss in adsorption capacity. • TiO 2 /BiOI exhibited superior recyclability (>98%) up to 10 cycles of photo-regeneration and re-adsorption. • Key removal mechanism of tetracyclines was detailed. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Ag NPs confined in shell-in-shell hollow TiO 2 photocatalyst was constructed. • The photocatalyst exhibited a complete degradation of tetracycline. • The excellent recyclability even after acid treatment was obtained. • TC degradation mechanism and pathway was proposed. • This work opened a new pathway for exploring other photocatalysts with two shells. Abstract The complete degradation of tetracycline still is a challenge for TiO 2 -based photocatalysts under simulated solar light irradiation. To tackle this challenge, we devise Ag nanoparticles (Ag NPs) confined in shell-in-shell hollow TiO 2 photocatalyst (HTAT). This strategy mainly involves the construction of CPS@TiO 2 core-shell composites, the form of TiO 2 inner shell, AgNPs loading by photo-deposition, the assembly of TiO 2 outer shell, and phase transition of anatase TiO 2 by calcination at 450℃. All characterizations including TEM, STEM Mapping, BET, and XPS confirm the unique structure of the as-synthesized HTAT photocatalyst. As expected, the complete degradation of tetracycline (TC and TCH) can be realized by using HTAT photocatalyst under simulated solar light irradiation because its TiO 2 two shells simultaneously take part in the photodegrading reaction of TC or TCH. The transformation intermediates and degradation pathway were analyzed by LC/MS. Our work effectively overcomes the disadvantages of many previously reported TiO 2 -based photocatalysts for the incomplete degradation of tetracycline. [ABSTRACT FROM AUTHOR]

A new protocol for constructing sandwich-like SiO 2 -Ag@TiO 2 hollow spheres (SAT) is introduced, in which SiO 2 acts as an efficient support for the Ag nanoparticles (Ag NPs) immobilization, while TiO 2 maintains its hierarchical structure and prevents the aggregation of Ag NPs during the photocatalytic reaction. As a photocatalytic agent, the inner and outer surfaces of TiO 2 can be fully occupied by pollutants molecules because of its unique structure, which faster boosts the photo-generated electrons to transfer the substrates, leading to an enhanced photocatalytic performance. Compared with Ag NPs deposited on the surface of SiO 2 @TiO 2 (STA), the as-synthesized SAT exhibits a markedly enhanced visible-light and UV light activity than STA for degrading tetracycline and traditional dyes. The excellent photocatalytic performances are ascribed to the enhanced transport paths of photo-generated electrons, reduced recombination probability of e − /h + pairs, and decreased threat of oxidation and corrosion. Especially, the SAT still maintains its photocatalytic efficiency after five consecutive runs even though the sample is recovered under visible-light irradiation, far beyond the reusability of STA under the same conditions. Therefore, the outstanding photocatalytic activity and excellent recyclability make SAT more potential to purify aquatic contaminants and to meet the demands of future environmental issues. [ABSTRACT FROM AUTHOR]

[Display omitted] • The p-n heterojunction Bi 2 O 3 /Ti3+-TiO 2 photocatalyst was reported by a facile method. • The Bi 2 O 3 /Ti3+-TiO 2 enabled the complete removal (100%) of tetracyclines under visible light. • The effect of environmental factors on the photodegradation of tetracyclines was detailed. • The mechanism on photodegradation was analyzed through LC–MS spectrum. The search for a highly active visible-light photocatalyst toward the complete degradation of antibiotic residuals remains a challenging task due to the fast emergence of antibiotic resistance. To address the problem, we explore a novel p-n heterojunction visible-light photocatalyst by coupling a p-type Bi 2 O 3 with an n-type Ti3+ self-doped TiO 2 porous material. The as-synthesized photocatalyst exhibits a narrowed bandgap (~2.89 eV) and enhanced visible-light absorption, leading to the complete degradation (100%) of antibiotics under visible light irradiation (λ > 420 nm) and excellent recyclability (98%) because of the synergistic effect of Ti3+ self-doping and p-n heterojunction. The results effectively work out the challenging task of the incomplete removal of tetracyclines over almost all of the reported visible-light photocatalysts. Additionally, the effects of antibiotics mixture, pH value, inorganic ions, water matrix, and outdoor light on the degradation of tetracyclines were also detailed. Especially, the transformation pathways and degradation mechanism of tetracycline were revealed in depth via trapping experiments and photoelectrochemical characterizations. Therefore, this work provides a new insight in exploring excellent photocatalysts to realize the complete removal of other refractory organic pollutants under visible light. [ABSTRACT FROM AUTHOR]