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Potassium/sodium poly-(heptazine imide) (K,Na-PHI) nanoparticles were found to possess peroxidase-like activity for the first time. In the presence of hydrogen peroxide (H2O2), K,Na-PHI nanoparticles can produce hydroxyl radicals, oxidizing 3,3′,5,5′-tetramethylbenzidine (TMB) to form blue-oxidized TMB. Based on the property of K,Na-PHI nanoparticles, a colorimetric biosensor was developed to detect Escherichia coli O157:H7 (E. coli O157) selectively. In the biosensor, K,Na-PHI nanoparticles were employed as a peroxidase mimic and an aptamer as a recognition element. Bacteria can enhance the peroxidase-like activity of dual-aptamer modified K,Na-PHI (aptamer1,2–K,Na-PHI) because they can capture aptamer1,2–K,Na-PHI and TMB, increasing the local concentrations of aptamer1,2–K,Na-PHI and their substrate TMB, promoting the formation of oxidized products of TMB in the catalytic system. In the biosensor, calcium peroxide was utilized to provide a source of H2O2 due to its long shelf life and safe handling properties, making the biosensor convenient for on-the-spot detection, especially when long-term storage is required. Furthermore, a portable device costing $122.8 was self-designed to increase the convenience of the biosensor in on-site detection, averting the need for expensive laboratory equipment and enabling even nonexperts to use it effectively. The biosensor exhibited a limit of detection of 85 cfu·mL–1 and the detection process took 16 min. Its feasibility was verified by analyzing E. coli O157 in egg white, tofu, and soybean milk samples, with recoveries ranging from 94.1 to 110%. Therefore, the biosensor holds great potential for the on-the-spot detection of bacteria in actual food samples. [ABSTRACT FROM AUTHOR]

This research constructed a novel O3/CaO2/ HCO 3 − system to degrade antibiotic oxytetracycline (OTC) in water. The results indicated that CaO2 and HCO 3 − addition could promote OTC degradation in an O3 system. There is an optimal dosage of CaO2 (0.05 g/L) and HCO 3 − (2.25 mmol/L) that promotes OTC degradation. After 30 min of treatment, approximately 91.5% of the OTC molecules were eliminated in the O3/CaO2/ HCO 3 − system. A higher O3 concentration, alkaline condition, and lower OTC concentration were conducive to OTC decomposition. Active substances including ·OH, 1O2, · O 2 − , and · HCO 3 − play certain roles in OTC degradation. The production of ·OH followed the order: O3/CaO2/ HCO 3 − > O3/CaO2 > O3. Compared to the sole O3 system, TOC and COD were easier to remove in the O3/CaO2/ HCO 3 − system. Based on DFT and LC-MS, active species dominant in the degradation pathways of OTC were proposed. Then, an evaluation of the toxic changes in intermediates during OTC degradation was carried out. The feasibility of O3/CaO2/ HCO 3 − for the treatment of other substances, such as bisphenol A, tetracycline, and actual wastewater, was investigated. Finally, the energy efficiency of the O3/CaO2/ HCO 3 − system was calculated and compared with other mainstream processes of OTC degradation. The O3/CaO2/ HCO 3 − system may be considered as an efficient and economical approach for antibiotic destruction. [ABSTRACT FROM AUTHOR]

Metal peroxide-based nanomedicines have emerged as promising theranostic agents for cancer due to their multifunctional properties, including the generation of bioactive small molecules such as metal ions, H2O2, O2, and OH–. Among these metal peroxides, calcium peroxide (CaO2) nanomedicines have attracted significant attention due to their facile synthesis and good biocompatibility. CaO2 nanoparticles have been explored for cancer treatment through three main mechanisms: (1) the release of O2, which helps alleviate tumor hypoxia and enhances oxygen-dependent therapies such as chemotherapy, photodynamic therapy, and immunotherapy; (2) the generation of H2O2, a precursor for ·OH generation, which enables cancer chemodynamic therapy; and (3) the release of Ca2+ ions, which induce calcium overload and promote cell apoptosis (called ion-interference therapy). This review provides a comprehensive summary of recent examples of CaO2 nanoparticle-based cancer therapeutic strategies, as well as discusses the challenges and future directions in the development of CaO2 nanomedicines for cancer treatment. [ABSTRACT FROM AUTHOR]

Bone defects resulting from trauma, disease, or aging present significant challenges in the clinic. Although biomaterial scaffolds for bone-tissue engineering have shown promising results, challenges remain, including the need for adequate mechanical strength and suitable bioactive agents within scaffolds to promote bone formation. Oxygen is a critical factor for successful bone formation, and low oxygen tension inhibits it. In this study, we developed gelatin methacryloyl (GelMA) hydrogel-impregnated electrospun polycaprolactone (PCL) scaffolds that can release oxygen over 3 weeks. We investigated the potential of composite scaffolds for cell survival in bone-tissue engineering. Our results showed that the addition of an increased amount of CaO2 nanoparticles to the PCL scaffolds significantly increased oxygen generation, which was modulated by GelMA impregnation. Moreover, the resulting scaffolds showed improved cytocompatibility, pre-osteoblast adhesion, and proliferation under hypoxic conditions. This finding is particularly relevant since hypoxia is a prevalent feature in various bone diseases. In addition to providing oxygen, CaO2 nanoparticles also act as reinforcing agents improving the mechanical property of the scaffolds, while the incorporation of GelMA enhances cell adhesion and proliferation properties. Overall, our newly developed self-oxygenating composite biomaterials are promising scaffolds for bone-tissue engineering applications. [ABSTRACT FROM AUTHOR]

This research constructed a novel O3/CaO2/HCO3− system to degrade antibiotic oxytetracycline (OTC) in water. The results indicated that CaO2 and HCO3− addition could promote OTC degradation in an O3 system. There is an optimal dosage of CaO2 (0.05 g/L) and HCO3− (2.25 mmol/L) that promotes OTC degradation. After 30 min of treatment, approximately 91.5% of the OTC molecules were eliminated in the O3/CaO2/HCO3− system. A higher O3 concentration, alkaline condition, and lower OTC concentration were conducive to OTC decomposition. Active substances including ·OH, 1O2, ·O2−, and ·HCO3− play certain roles in OTC degradation. The production of ·OH followed the order: O3/CaO2/HCO3− > O3/CaO2 > O3. Compared to the sole O3 system, TOC and COD were easier to remove in the O3/CaO2/HCO3− system. Based on DFT and LC-MS, active species dominant in the degradation pathways of OTC were proposed. Then, an evaluation of the toxic changes in intermediates during OTC degradation was carried out. The feasibility of O3/CaO2/HCO3− for the treatment of other substances, such as bisphenol A, tetracycline, and actual wastewater, was investigated. Finally, the energy efficiency of the O3/CaO2/HCO3− system was calculated and compared with other mainstream processes of OTC degradation. The O3/CaO2/HCO3− system may be considered as an efficient and economical approach for antibiotic destruction.

Introduction: Reactive oxygen species (ROS)-mediated therapies have typically been considered as noninvasive tumor treatments owing to their high selectivity and efficiency. However, the harsh tumor microenvironment severely impairs their efficiency.Methods: Herein, the biodegradable Cu-doped zeolitic imidazolate framework-8 (ZIF-8) was synthesized for loading photosensitizer Chlorin e6 (Ce6) and CaO2 nanoparticles, followed by surface decoration by hyaluronic acid (HA), obtaining HA/CaO2-Ce6@Cu-ZIF nano platform.Results and Discussion: Once HA/CaO2-Ce6@Cu-ZIF targets tumor sites, the degradation of Ce6 and CaO2 release from the HA/CaO2-Ce6@Cu-ZIF in response to the acid environment, while the Cu2+ active sites on Cu-ZIF are exposed. The released CaO2 decompose to generate hydrogen peroxide (H2O2) and oxygen (O2), which alleviate the insufficiency of intracellular H2O2 and hypoxia in tumor microenvironment (TME), effectively enhancing the production of hydroxyl radical (•OH) and singlet oxygen (1O2) in Cu2+-mediated chemodynamic therapy (CDT) and Ce6-induced photodynamic therapy (PDT), respectively. Importantly, Ca2+ originating from CaO2 could further enhance oxidative stress and result in mitochondrial dysfunction induced by Ca2+ overloading.Conclusion: Thus, the H2O2/O2 self-supplying and Ca2+ overloading ZIF-based nanoplatform for cascade-amplified CDT/PDT synergistic strategy is promising for highly efficient anticancer therapy.

In recent years, calcium peroxide (CaO2) has attracted widespread attention in the medical community due to its excellent antitumor and antibacterial properties, and has gradually become a hot research topic in the biomedical field. CaO2 reacts with water (H2O) to produce calcium ion (Ca2+), oxygen (O2), and hydrogen peroxide (H2O2), where Ca2+ is suitable for calcium death caused by calcium overload, O2 is suitable for O2-dependent anticancer therapy, and H2O2 is suitable for H2O2-dependent anticancer therapy. In addition, H2O2 can also be used in the antibacterial field to treat bacterial infections. All these make the CaO2 to become a kind of excellent antitumor and antibacterial drug. This study mainly reviews the preparation and surface modification of CaO2, probes into the latest progress about CaO2 nanoparticles in the field of tumor treatment and antimicrobial therapy. Finally, the challenges that CaO2 still faces in the future research field are clarified, and its prospects are forecasted.

Bone defects resulting from trauma, disease, or aging present significant challenges in the clinic. Although biomaterial scaffolds for bone-tissue engineering have shown promising results, challenges remain, including the need for adequate mechanical strength and suitable bioactive agents within scaffolds to promote bone formation. Oxygen is a critical factor for successful bone formation, and low oxygen tension inhibits it. In this study, we developed gelatin methacryloyl (GelMA) hydrogel-impregnated electrospun polycaprolactone (PCL) scaffolds that can release oxygen over 3 weeks. We investigated the potential of composite scaffolds for cell survival in bone-tissue engineering. Our results showed that the addition of an increased amount of CaO2 nanoparticles to the PCL scaffolds significantly increased oxygen generation, which was modulated by GelMA impregnation. Moreover, the resulting scaffolds showed improved cytocompatibility, pre-osteoblast adhesion, and proliferation under hypoxic conditions. This finding is particularly relevant since hypoxia is a prevalent feature in various bone diseases. In addition to providing oxygen, CaO2 nanoparticles also act as reinforcing agents improving the mechanical property of the scaffolds, while the incorporation of GelMA enhances cell adhesion and proliferation properties. Overall, our newly developed self-oxygenating composite biomaterials are promising scaffolds for bone-tissue engineering applications.

[Display omitted] • The CaO 2 -Fenton-like system could promote humification in the co-composting. • Fe(Ⅱ), Ca2+, and humic substances could decrease Cr(VI). • The enrichment of Cr(VI) reducing microorganisms promoted the reduction of Cr(VI). • Biotic and abiotic mechanisms for Cr(VI) reduction and immobilization are proposed. The current research studied how Fe 3 O 4 nanomaterials (NMs) and CaO 2 affect humification and Cr(VI) immobilization and reduction during the composting of oil-tea Camellia meal and Cr-contaminated soil. The results showed that Fe 3 O 4 NMs and CaO 2 successfully construct a Fenton-like reaction in this system. The excitation-emission matrix-parallel factor (EEM-PARAFAC) demonstrated that this Fenton-like treatment increased the generation of humic acids and accelerated the humification. Meantime, RES-Cr increased by 5.91 % and Cr(VI) decreased by 16.36 % in the treatment group with CaO 2 and Fe 3 O 4 NMs after 60 days. Moreover, the microbial results showed that Fe 3 O 4 NMs and CaO 2 could promote the enrichment of Cr(VI) reducing bacteria, e.g., Bacillus , Pseudomonas , and Psychrobacter , and promote Cr(VI) reduction. This study gives a novel view and theoretical reference to remediate Cr(VI) pollution through composting. [ABSTRACT FROM AUTHOR]

Highly purified CaO 2 derived from waste oyster shells was prepared for realizing "Turning waste to wealth" in high value reutilization of waste shells and "Treating pollution with waste" in efficient degradation of pollutants. [Display omitted] • CaO 2 was prepared derived from waste oyster shells with high purity. • CaO 2 derived from waste oyster shells showed a highly catalytic ability in the degradation of organic pollutions in the presence of Fe2+. • The high purity of CaO 2 can facilitate the release of H 2 O 2 and promote the generation of more active species. • ⋅OH, ⋅O 2 – and 1O 2 played key roles in the Fenton-like catalytic process. • "Turning waste to wealth" and "Treating pollution with waste" were "One Stone Two Birds" realized. In recent years, CaO 2 has been frequently used as a substitute for H 2 O 2 to address the limitations of H 2 O 2. However, commercially available CaO 2 are facing the shortcomings of low purity and limited preparation conditions. Oyster shells can provide superior and abundant biomass calcium element with low cost for developing CaO 2. In this work, highly purified CaO 2 functional biomaterials were prepared via a facile approach derived from waste oyster shells, which were applied in a Fenton-like system to remove organic pollutants. Experimental results indicated that the oyster shells-derived CaO 2 with 100% purity exhibited a greatly enhanced catalytic performance compared with other CaO 2 materials in Fenton-like catalytic degradation of organic pollutants, which can be completely removed within 60 s. The high purity of CaO 2 would facilitate the release of H 2 O 2 during the Fenton-like catalytic reaction and promote the generation of more active species to oxidize pollutants. Besides, the abundant trace metal elements originated from oyster shells can further motivate the Fenton-like reaction and accelerate the degradation of pollutants, endowing oyster shells-derived CaO 2 an excellent catalytic activity. Furthermore, the Fenton-like catalytic mechanism was proposed on basis of tests of radicals trapping and electron spin resonance, validating the vital roles of ⋅OH, ⋅O 2 – and 1O 2 generated throughout the reaction process. This work not only provides a novel and low-cost approach to exploit CaO 2 with highly efficient catalytic ability, but also realizes the effective resource utilization of waste shells. [ABSTRACT FROM AUTHOR]

Phenols are toxic products derived from a wide range of industrial activities and the entry of these contaminants into the environment is seriously hazardous for both human and aquatic ecosystems. This study presents the use of a phenol-degrading consortium surrounded in an innovative "Small Bioreactor Chambers" (SBCs) along with biostimulation for phenol bioremediation from contaminated groundwater. To investigate the effect of biostimulation, synthesized-calcium peroxide (Ca02) nanoparricies were applied. The phenol-degrading consortium, was successfully isolated froni a water well located in Iran. The highest growth rate and phenol degradation of the ph100-consortium were observed at 15 °C and pH 7.5 in the presence of 500 mg·L-1 of powdered CaO2 and 100 mg·L-1 of phenol as a sole source of carbon. Next-generation sequencing (NGS) analysis of the consortium revealed that Proteobacteria and Bacteroidetes with 75.3% and 16.2% relative abundance were the dominant phyla in the ph100-consortium, respectively. Experimental results indicated that 100% of the contaminant (100 mg·LF) was successfully removed from groundwater using encapsulated CaO2 within 60 days with the negligible negative impacts on the microbial population. Furthermore, the highest biodegradation percentage were achieved during incubation of SBCs a medium supplemented with 500 mg·L-1 CaO2 Powder in 25th days of experiment. These results provide certain evidence for a successful simultaneous application of biostimulation and bioaugmentation processes through SBCs for contaminated water treatinent. [ABSTRACT FROM AUTHOR]

Drug transportation is impeded by various barriers in the hypoxic solid tumor, resulting in compromised anticancer efficacy. Herein, a solid lipid monostearin (MS)-coated CaO 2 /MnO 2 nanocarrier was designed to optimize doxorubicin (DOX) transportation comprehensively for chemotherapy enhancement. The MS shell of nanoparticles could be destroyed selectively by highly-expressed lipase within cancer cells, exposing water-sensitive cores to release DOX and produce O 2. After the cancer cell death, the core-exposed nanoparticles could be further liberated and continue to react with water in the tumor extracellular matrix (ECM) and thoroughly release O 2 and DOX, which exhibited cytotoxicity to neighboring cells. Small DOX molecules could readily diffuse through ECM, in which the collagen deposition was decreased by O 2 -mediated hypoxia-inducible factor-1 inhibition, leading to synergistically improved drug penetration. Concurrently, DOX-efflux-associated P-glycoprotein was also inhibited by O 2 , prolonging drug retention in cancer cells. Overall, the DOX transporting processes from nanoparticles to deep tumor cells including drug release, penetration, and retention were optimized comprehensively, which significantly boosted antitumor benefits. Synergistic drug penetration, sufficient drug release, and prolonged drug retention were concurrently realized by a smart O 2 -generating nanocarrier, contributing to comprehensively optimized drug transportation and thereby improved chemotherapy. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract The conversion of endogenous H2O2 into toxic hydroxyl radical (•OH) via catalytic nanoparticles is explored for tumor therapy and received considerable success. The intrinsic characteristics of microenvironment in tumor cells, such as limited H2O2 and overexpressed glutathione (GSH), hinder the intracellular •OH accumulation and thus weaken therapeutic efficacy considerably. In this study, fine CaO2 nanoparticles with Cu–ferrocene molecules at the surface (CaO2/Cu–ferrocene) are successfully designed and synthesized. Under an acidic condition, the particles release Ca2+ ions and H2O2 in a rapid fashion, while they can remain stable in neutral. In addition, agitated production of •OH occurs following the Fenton reaction of H2O2 and ferrocene molecules, and GSH is consumed by Cu2+ ions to avoid the potential •OH consumption. More interestingly, in addition to the exogenous Ca2+ released by the particles, the enhanced •OH production facilitates intracellular calcium accumulation by regulating Ca2+ channels and pumps of tumor cells. It turns out that promoted •OH induction and intracellular calcium overload enable significant in vitro and in vivo antitumor phenomena.

The conversion of endogenous H2O2 into toxic hydroxyl radical (•OH) via catalytic nanoparticles is explored for tumor therapy and received considerable success. The intrinsic characteristics of microenvironment in tumor cells, such as limited H2O2 and overexpressed glutathione (GSH), hinder the intracellular •OH accumulation and thus weaken therapeutic efficacy considerably. In this study, fine CaO2 nanoparticles with Cu–ferrocene molecules at the surface (CaO2/Cu–ferrocene) are successfully designed and synthesized. Under an acidic condition, the particles release Ca2+ ions and H2O2 in a rapid fashion, while they can remain stable in neutral. In addition, agitated production of •OH occurs following the Fenton reaction of H2O2 and ferrocene molecules, and GSH is consumed by Cu2+ ions to avoid the potential •OH consumption. More interestingly, in addition to the exogenous Ca2+ released by the particles, the enhanced •OH production facilitates intracellular calcium accumulation by regulating Ca2+ channels and pumps of tumor cells. It turns out that promoted •OH induction and intracellular calcium overload enable significant in vitro and in vivo antitumor phenomena. [ABSTRACT FROM AUTHOR]

• Developed oxalic acid (OA) chelated electrochemical (EF) released Fe2+ activated CaO 2 pre-conditioned sludge process. • EF-CaO 2 /OA effectively enhanced sludge dewaterability at neutral pH. • EF-CaO 2 /OA provides durable and effective oxidizing power. • End-of-conditioned sludge was still pH-neutral. • Altered protein secondary structure transforms sludge from hydrophilic to hydrophobic. In this study, we investigated the efficiency of activation of CaO 2 by oxalic acid (OA) chelated with electrochemically (EF)-released Fe2+ (EF-CaO 2 /OA) in improving the performance of sludge dewatering under neutral conditions. We also explored the mechanism of OA-reinforcement of EF-CaO 2 in enhancing the performance of wastewater-activated sludge dewatering by investigating the water content (Wc), specific resistance to filtration (SRF), pH, bound water content, extracellular polymers in the sludge, the secondary structure of proteins, the soluble ferric ions, and the morphology of the sludge. The EF-CaO 2 /OA process was better than the EF-CaO 2 process in terms of sludge dewatering. OA introduction significantly inhibited the increase of solution pH, which in turn promoted CaO 2 dissolution and persistent H 2 O 2 generation. The persistent oxidative reaction contributed to the degradation of hydrophilic protein fractions in EPS and the reduction of the proportion of hydrophilic structures in the secondary structure of proteins, which in turn improved the hydrophobicity of the sludge. The changing profile of DNA content in EPS proved that EF-CaO 2 /OA led to the damage of more sludge cells. It suggested that OA enhanced the oxidizing efficacy of EF-CaO 2 , which in turn promoted the release of bound water from more sludge cells. Moreover, OA significantly increased the amount of dissolved iron in solution by chelating the electrochemically released iron, which contributed to the stabilization of the oxidation reaction. Under the optimal conditions, sludge Wc and SRF treated by EF-CaO 2 /OA were reduced by 30.1% and 96.9%, respectively, and the dewatered sludge cake remained neutral. In conclusion, EF-CaO 2 /OA may be an efficient and feasible technique for deep sludge dewatering. [ABSTRACT FROM AUTHOR]

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Abstract Combined chemo/chemodynamic therapy is a promising strategy to achieve an improved anticancer effect. However, the hypoxic microenvironment and limited amount of H2O2 in most solid tumors severely restrict the efficacy of this treatment. Herein, the construction of a nanocatalytic medicine, CaO2@DOX@ZIF‐67, via a bottom‐up approach is described. CaO2@DOX@ZIF‐67 simultaneously supplies O2 and H2O2 to achieve improved chemo/chemodynamic therapy. In the weakly acidic environment within tumors, CaO2@DOX@ZIF‐67 is broken down to rapidly release the Fenton‐like catalyst Co2+ and the chemotherapy drug doxorubicin (DOX). The unprotected CaO2 reacts with H2O to generate both O2 and H2O2. The generated O2 relieves the hypoxia in the tumor and further improve the efficacy of DOX. Meanwhile, the generated H2O2 reacts with Co2+ ions to produce highly toxic •OH through a Fenton‐like reaction, resulting in improved chemodynamic therapy.

A near-infrared-responsive photocatalyst of SnFe 2 O 4 @CaO 2 with Fenton-like property and self-oxygen supply is successfully prepared and applied for dye degradation and sterilization in wastewater. [Display omitted] • CaO 2 has synergistic effect with SnFe 2 O 4 by providing H 2 O 2 and dissolved oxygen. • SnFe 2 O 4 could trigger Fenton-like reaction and NIR-driven photocatalytic performance. • Photocatalytic sterilization avoiding drug resistant & improving water purification. Near-infrared-driven photocatalysis represents the maximized utilization of solar energy and how to enhance its activity is of great significance. To achieve this, we design a synergetic composite of SnFe 2 O 4 @CaO 2 in this work. CaO 2 layer could react with H 2 O to generate H 2 O 2 and O 2. Then, SnFe 2 O 4 could trigger Fenton-like reaction to convert H 2 O 2 to OH and O 2 – for the pollutant degradation, which is a similar process to the advanced oxidation process. Additionally, SnFe 2 O 4 is a NIR-responsive photocatalyst, which could convert dissolved oxygen into reactive oxygen species (ROS) under irradiation. Thus, the synergetic action between CaO 2 and SnFe 2 O 4 gives a better catalytic outcome. The experimental results demonstrate that OH and O 2 – are the main free radicals of the reaction. The kinetics characteristics of the free radicals generation are examined and a possible photocatalysis degradation mechanism is proposed. Moreover, the SnFe 2 O 4 @CaO 2 exhibits excellent photocatalytic sterilization performance. Therefore, the SnFe 2 O 4 @CaO 2 achieved integrated treatment of wastewater. [ABSTRACT FROM AUTHOR]

To improve the dissolved oxygen of groundwater for in situ manganese removal, we prepared oxygen slow-releasing materials calcium peroxide/paraffin wax (CaO2/PW) by a physical mixing method under heating conditions. The properties of CaO2/PW were investigated by oxygen-releasing experiments under dynamic conditions and filtration experiments. The surface microstructures were characterized using scanning electron microscopy and energy-dispersive spectrometry. CaO2/PW exhibited good oxygen-releasing performance and effective pH control ability. Moreover, CaO2/PW met the requirement of dissolved oxygen when the water flow velocity was 39.77 m/h, the initial dosage was 4 g/L, and the calcium peroxide:paraffin wax:kaolin:river sand weight ratio was 1.67:50:2:30. Under the influence of flow velocity, the initial dosage, and raw material ratio, the Elovich equation well fitted oxygen release with correlation coefficients above 0.9567. The release kinetic equation of CaO2/PW was determined on MATLAB. In situ simulation experiments confirmed the feasibility and effectiveness of CaO2/PW for in situ manganese removal from groundwater. This study can be used as a reference for practical application of this technology for groundwater restoration. [ABSTRACT FROM AUTHOR]

The thermodynamic and kinetic performance of the oxidative absorbent S2O82‐/CaO2 for NO removal was evaluated. The results indicated that the optimal molar ratio of Na2S2O8/CaO2 was 0.1:0.2 mol/mol. The experimental results showed that the combination of Na2S2O8 and CaO2 had a positive synergistic effect on the NO removal. The results of the thermodynamic calculation verified that the use of the oxidative absorbent S2O82‐/CaO2 was effective for NO removal. The results of the kinetic study showed that the NO reaction was a 1.1‐order equation and the average activation energy of the reaction was 53.0 kJ/mol. The oxidative absorbent S2O82‐/CaO2 shows potential for the simultaneous wet removal of NO and SO2 with high efficiency, no secondary pollution, and low cost. [ABSTRACT FROM AUTHOR]

Abstract This study investigated the applicability of synthesized calcium peroxide (CaO 2) nanoparticles for naphthalene bioremediation by permeable reactive barrier (PRB) from groundwater. According to the batch experiments the application of 400 mg/L of CaO 2 nanoparticles was the optimum concentration for naphthalene (20 mg/L) bioremediation. Furthermore, the effect of environmental conditions on the stability of nanoparticles showed the tremendous impacts of the initial pH and temperature on the stability and oxygen releasing potential of CaO 2. Therefore, raising the initial pH from 3 to 12 elevated the dissolved oxygen from 4 to 13.6 mg/L and the stability of nanoparticles was significantly improved around 70 d. Moreover, by increasing the temperature from 4 to 30 °C, the stability of CaO 2 declined from 120 to 30 d. The continuous-flow experiments revealed that the naphthalene-contaminated groundwater was completely bio-remediated in the presence of CaO 2 nanoparticles and microorganisms from the effluent of the column within 50 d. While, the natural remediation of the contaminant resulted in 19.7% removal at the end of the experiments (350 d). Additionally, the attached biofilm on the surface of the PRB zone was studied by scanning electron microscopy (SEM) which showed the higher biofilm formation on the pumice surfaces in the bioremediation column in comparison to the natural remediation column. The physic-chemical characteristics of the effluents from each column was also analyzed and indicated no negative impact of the bioremediation process on the groundwater. Consequently, the present paper provides a comprehensive study on the application of the CaO 2 nanoparticles in PAH-contaminated groundwater treatment. Graphical abstract Image 1 Highlights • Temperature and pH of the groundwater were identified as the important factors on the stability of calcium peroxide nanoparticles. • More oxygen were generated from calcium peroxide under alkaline condition and lower temperature. • Naphthalene-contaminated groundwater was remediated by CaO 2 nanoparticles using permeable reactive barrier after 50 days. • Indigenous microbial groundwater showed a significant impact on the naphthalene remediation in aerobic condition. [ABSTRACT FROM AUTHOR]

[Display omitted] • 0.25 g/g VSS CaO 2 reduced by 80.5% of H 2 S production from anaerobic fermentation. • CaO 2 addition destroyed sludge EPS structure and caused cell lysis. • The abundance and activity of S2− producers were reduced by CaO 2 addition. • CaO 2 addition promoted metal ions release and changed sulfur transformation. • Organic sulfur hydrolysis and inorganic sulfate reduction were inhibited. Calcium peroxide (CaO 2) addition is widely regarded as a high-efficient sludge treatment method to degrade pollutants and enhance resource recovery. In this study, it was further found that CaO 2 addition changed sulfur distribution during sludge anaerobic treatment, which promoted sulfur flow from sludge solid to liquid phase but significantly inhibited toxic hydrogen sulfide (H 2 S) gas production. With CaO 2 addition increased from 0 to 0.25 g/g VSS, the accumulated H 2 S yield decreased from 314.6 × 10−4 to 61.3 × 10−4 mg/g VSS while the accumulated SCFAs and hydrogen yields increased from 46.2 to 266.5 mg COD/g VSS, and 0.9 to 10.2 mL/g VSS. Mechanism analysis showed that the released OH– and oxidizing substances (e.g., ·OH and ·O 2 –) firstly destroyed functional groups and hydrogen bonding networks contained in sludge EPS, with the contents of C=O group, β-sheet and α-Helix being reduced by 24%, 19.7%, and 23.2%, respectively. This caused the cracking of sludge EPS and releases of soluble metal ions (e.g., Al, Mg, and Fe). The released metal ions in alkaline environment promoted the transformation of H 2 S gas and dissolved sulfide to metal sulfide, which was one important reason to reduce H 2 S gas release. Then, the free radicals further attacked sludge cells without EPS protection and caused cell lysis. Flow cytometry analysis showed that 0.25 g/g VSS CaO 2 reduced the rate of living cells from 90.7% to 81.4%. Microbial analysis unveiled that CaO 2 reduced the content of S2− producers (e.g., Desulfobulbus and Desulfovibrio) and the expression of related genes (e.g., PepD and Sat). Moreover, the activities of S2− producers, e.g., methionine lyase and adenosine-5′-phosphosulfate reductase also reduced by 41.3% and 64.8% with 0.25 g/g VSS CaO 2 addition. These findings provide new insights into CaO 2 -based sludge treatment and might have significant implications for sludge treatment. [ABSTRACT FROM AUTHOR]

Titanium-based implants often lead to premature implant failure due to the lack of antimicrobial, osteogenic, and angiogenic properties. To this end, a new strategy was developed to fabricate CaO 2 @ZIF-67-HA-ADH coating on titanium surfaces by combining calcium peroxide (CaO 2 ) nanoparticles, zeolite imidazolate framework-67 (ZIF-67), and the chemical coupling hyaluronic acid-adipic acid dihydrazide (HA-ADH). We characterized CaO 2 @ZIF-67-HA-ADH with scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma-atomic emission spectrometry (ICP-AES). The results demonstrated that CaO 2 @ZIF-67-HA-ADH was pH-sensitive and decomposed rapidly under acidic conditions, and it released inclusions slowly under neutral conditions. Antibacterial experiments showed that the CaO 2 @ZIF-67-HA-ADH coating had excellent antibacterial properties and effectively killed methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa (PAO-1). Cell experiments revealed that the CaO 2 @ZIF-67-HA-ADH coating promoted pro-osteoblast adhesion, proliferation, and differentiation and also promoted the migration and angiogenesis of human umbilical vein endothelial cells (HUVECs), exhibiting excellent osteogenic and angiogenic properties. In in vivo animal implantation experiments, the CaO 2 @ZIF-67-HA-ADH coating exhibited strong antimicrobial activity early after implantation and excellent osseointegration later after implantation. In conclusion, the pH-responsive CaO 2 @ZIF-67-HA-ADH coating conferred excellent antibacterial, osteogenic, and angiogenic properties to titanium implants, which effectively enhanced osseointegration of the implants and prevented bacterial infection; the coating shows promise for use in the treatment of bone defects.

Metal peroxide-based nanomedicines have emerged as promising theranostic agents for cancer due to their multifunctional properties, including the generation of bioactive small molecules such as metal ions, H 2 O 2 , O 2 , and OH - . Among these metal peroxides, calcium peroxide (CaO 2 ) nanomedicines have attracted significant attention due to their facile synthesis and good biocompatibility. CaO 2 nanoparticles have been explored for cancer treatment through three main mechanisms: (1) the release of O 2 , which helps alleviate tumor hypoxia and enhances oxygen-dependent therapies such as chemotherapy, photodynamic therapy, and immunotherapy; (2) the generation of H 2 O 2 , a precursor for ·OH generation, which enables cancer chemodynamic therapy; and (3) the release of Ca 2+ ions, which induce calcium overload and promote cell apoptosis (called ion-interference therapy). This review provides a comprehensive summary of recent examples of CaO 2 nanoparticle-based cancer therapeutic strategies, as well as discusses the challenges and future directions in the development of CaO 2 nanomedicines for cancer treatment., (© 2023 IOP Publishing Ltd.)

CaO 2 has been widely used as an oxygen-releasing material in bioremediation to improve the aerobe activity, but conventional encapsulation methods are difficult to control the oxygen-releasing rate and realize the full conversion of CaO 2. In this work, innovative biochar-loaded CaO 2 was prepared by an in-situ precipitation method. The biochars were modified using base-/acid-treatment to establish the relationship between the biochar properties and the oxygen releasing performance. Results indicated that increasing the oxygen content of biochars from 11% to 12% to ∼20% caused a significant rise in CaO 2 loading amount from ∼6 wt% to 13–14 wt%. The biochar with an average pore size equivalent to CaO 2 nanoparticle sizes (∼12 nm) exhibited the longest oxygen-releasing time of 7.5 d, while the others presented shorter releasing periods of < 2.4 d. Meanwhile, a higher oxygen content of biochar triggered a decrease in the oxygen-releasing amount. Results from bioremediation experiments indicated that when comparing with the pure CaO 2 material, the optimized loading material (CaO 2 @BC800) nearly doubled the amount of bacteria while negligibly changed the pH of solution, giving a significant increase in the removal of diesel oil pollutant. Correspondingly, the in-situ loading on biochar can facilely regulate the oxygen-releasing performance and enhance the removal efficiency of bioremediation. [Display omitted] ● Biochar-based CaO 2 were successfully prepared using an in-situ precipitation method. ● The raised O content of biochars increased the CaO 2 loading capacity. ● Mesopores similar in size to CaO 2 nanoparticles boosted the oxygen release time. ● Full conversion of CaO 2 was achieved for all the biochar-loaded materials. ● The optimized material boosted the removal of diesel oil during bioremediation. [ABSTRACT FROM AUTHOR]

Natural organic matter humic acid (HA) coupled with the inorganic metal oxides FeO x + MnO x will cause severe irreversible membrane fouling. Chemical cleaning is indispensable for the removal of irreversible membrane foulants and sustainable membrane filtration, while conventional cleaning methods have limitations with low cleaning efficiency, high reagents consumption and potential membrane damage. For the first time, calcium peroxide (CaO 2), a solid alternative for liquid hydrogen peroxide (H 2 O 2), is proposed for the membrane cleaning. For membranes fouled by HA, it is noteworthy that 40 mg/32.15 cm2 CaO 2 tablet without any other catalyst can restore the terminal membrane flux dramatically from 51% to 82% in only 5 min, which is far more than 3 wt% H 2 O 2 alone (only from 51% to 59%). Moreover, Fenton-like reaction induced by in-situ membrane foulants FeO x + MnO x further enhances the membrane flux from 53% to 97%. Based on HA oxidation tests and reactive species identification in CaO 2 tablets cleaning process for the case of HA-fouled membranes and HA + FeO x + MnO x -fouled membranes, singlet oxygen ( O 2 1) in CaO 2 system dominated the strong oxidation of electron-rich compounds HA, which plays a key role in membrane flux recovery. With involvement of FeO x + MnO x , signal intensities of free radicals such as hydroxyl radicals (O H •) are enhanced greatly, which further achieves more outstanding membrane cleaning performance. These results underline that the novel CaO 2 system provides a promising candidate for more portable and cost-effective membrane cleaning method in a nonradical pathway. [Display omitted] • A novel non-radical cleaning strategy using CaO 2 was proposed. • CaO 2 system achieves outstanding flux recovery from irreversible foulants. • Singlet oxygen was identified as the dominated reactive species for cleaning process. • Membrane foulants, FeO x and MnO x , could further increase permeate flux recovery. [ABSTRACT FROM AUTHOR]

Introduction: Reactive oxygen species (ROS)-mediated therapies have typically been considered as noninvasive tumor treatments owing to their high selectivity and efficiency. However, the harsh tumor microenvironment severely impairs their efficiency. Methods: Herein, the biodegradable Cu-doped zeolitic imidazolate framework-8 (ZIF-8) was synthesized for loading photosensitizer Chlorin e6 (Ce6) and CaO 2 nanoparticles, followed by surface decoration by hyaluronic acid (HA), obtaining HA/CaO 2 -Ce6@Cu-ZIF nano platform. Results and Discussion: Once HA/CaO 2 -Ce6@Cu-ZIF targets tumor sites, the degradation of Ce6 and CaO 2 release from the HA/CaO 2 -Ce6@Cu-ZIF in response to the acid environment, while the Cu 2+ active sites on Cu-ZIF are exposed. The released CaO 2 decompose to generate hydrogen peroxide (H 2 O 2 ) and oxygen (O 2 ), which alleviate the insufficiency of intracellular H 2 O 2 and hypoxia in tumor microenvironment (TME), effectively enhancing the production of hydroxyl radical (•OH) and singlet oxygen ( 1 O 2 ) in Cu 2+ -mediated chemodynamic therapy (CDT) and Ce6-induced photodynamic therapy (PDT), respectively. Importantly, Ca 2+ originating from CaO 2 could further enhance oxidative stress and result in mitochondrial dysfunction induced by Ca 2+ overloading. Conclusion: Thus, the H 2 O 2 /O 2 self-supplying and Ca 2+ overloading ZIF-based nanoplatform for cascade-amplified CDT/PDT synergistic strategy is promising for highly efficient anticancer therapy., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Liang, Cai, Tang, Su, Xie, Li and Liang.)

Decolorization of Acid Blue 161 (AB161) by solid peroxides such as CaO2 and Na2O2 catalyzed by iron in aqueous solution was investigated. The effect of initial pH, concentration of H2O2, Fe2+, and AB161 on the decolorization kinetics was investigated and compared with the results by liquid H2O2. The experimental results show that decolorization of AB161 follows the second-order kinetic. The second decolorization rate constants and oxidation efficiency at different initial pH, Fe2+, H2O2, and AB161 concentration were correlated with dimensionless ratios such as H2O2/Fe2+ or H2O2/AB161. About two dozens of correlation equations are developed in this paper to quantify the effect of the variables on the decolorization rate constants of AB161. Among solid peroxides such as CaO2 and Na2O2 and liquid H2O2, the optimal pH and [Fe2+] are 2.5 and 5.0 × 10−4 mol L−1, while the concentration of CaO2, Na2O2, and H2O2 is 0.30, 0.25 g L−1 and 3.1 × 10−3 mol L−1, respectively. Our experimental results show that decolorization kinetics of AB161 using liquid H2O2 is faster than that using CaO2 and Na2O2 catalyzed by Fe2+, while decolorization rate of AB161 by CaO2 is slightly faster than that by Na2O2 due to the fact that the CaO2 is a fine powder of an average diameter of 0.74 mm and Na2O2 is a particle with an average diameter of 1 mm. Regardless of the solid or liquid peroxide forms, e.g. CaO2, Na2O2, or liquid H2O2, the optimal molar ratio H2O2/Fe2+ of 12 obtained experimentally agreed reasonably with the theoretical predicted value of 11. In addition, the decolorization efficiency, η, is also not affected by the form of peroxides and decreases with the H2O2/AB161 when H2O2, Fe2+, and pH were fixed at 3.1 × 10−3, 5.0 × 10−4 mol L−1, and 2.5, respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • nCaO2@PDA composites with core–shell structure are prepared via a facile method. • The nCaO2@PDA-0.5/Fe(III) system is effective in RhB degradation in a wide pH range. • PDA can reduce Fe3 + effectively through phenol-quinone transformation. • The core–shell structure guarantees the high reaction rate between H2O2 and Fe2+. • The degradation mechanism of the nCaO2@PDA-0.5/Fe(III) system is proposed. Fenton (or Fenton-like) reaction is widely used to degrade organic pollutants in water. However, instability and insecurity of liquid H 2 O 2 , narrow pH range and the low circulation rate between Fe2+/Fe3+ have become the most critical limiting factors of this technology. To break this technical barrier, calcium peroxide nanoparticles @polydopamine composites (nCaO 2 @PDA) with core–shell structures were prepared, which showed desirable hydrogen peroxide (H 2 O 2) release performance as well as excellent activity for RhB degradation in a wide pH range of 2.0 ∼ 11.0 in the presence of Fe3+. By careful analysis the surface properties of PDA, the Fe2+ concentrations during reaction and the results of rational-designed control experiments, it is proved that PDA can reduce Fe3+ through the phenol-quinone transformation. More importantly, thanks to the unique core–shell structure, abundance of H 2 O 2 and Fe2+ are both available in the vicinity of nCaO 2 @PDA, ensuring the superior catalytic performance than that of nCaO 2. In addition, the HO• in solution rather than those adsorbed on PDA surface contribute most in the RhB degradation. [ABSTRACT FROM AUTHOR]

Drug transportation is impeded by various barriers in the hypoxic solid tumor, resulting in compromised anticancer efficacy. Herein, a solid lipid monostearin (MS)-coated CaO 2 /MnO 2 nanocarrier was designed to optimize doxorubicin (DOX) transportation comprehensively for chemotherapy enhancement. The MS shell of nanoparticles could be destroyed selectively by highly-expressed lipase within cancer cells, exposing water-sensitive cores to release DOX and produce O 2 . After the cancer cell death, the core-exposed nanoparticles could be further liberated and continue to react with water in the tumor extracellular matrix (ECM) and thoroughly release O 2 and DOX, which exhibited cytotoxicity to neighboring cells. Small DOX molecules could readily diffuse through ECM, in which the collagen deposition was decreased by O 2 -mediated hypoxia-inducible factor-1 inhibition, leading to synergistically improved drug penetration. Concurrently, DOX-efflux-associated P-glycoprotein was also inhibited by O 2 , prolonging drug retention in cancer cells. Overall, the DOX transporting processes from nanoparticles to deep tumor cells including drug release, penetration, and retention were optimized comprehensively, which significantly boosted antitumor benefits., Competing Interests: The authors have no conflicts of interest to declare., (© 2021 Chinese Pharmaceutical Association and Institute of Materia Medica, Chinese Academy of Medical Sciences. Production and hosting by Elsevier B.V.)

The conversion of endogenous H 2 O 2 into toxic hydroxyl radical ( • OH) via catalytic nanoparticles is explored for tumor therapy and received considerable success. The intrinsic characteristics of microenvironment in tumor cells, such as limited H 2 O 2 and overexpressed glutathione (GSH), hinder the intracellular • OH accumulation and thus weaken therapeutic efficacy considerably. In this study, fine CaO 2 nanoparticles with Cu-ferrocene molecules at the surface (CaO 2 /Cu-ferrocene) are successfully designed and synthesized. Under an acidic condition, the particles release Ca 2+ ions and H 2 O 2 in a rapid fashion, while they can remain stable in neutral. In addition, agitated production of • OH occurs following the Fenton reaction of H 2 O 2 and ferrocene molecules, and GSH is consumed by Cu 2+ ions to avoid the potential • OH consumption. More interestingly, in addition to the exogenous Ca 2+ released by the particles, the enhanced • OH production facilitates intracellular calcium accumulation by regulating Ca 2+ channels and pumps of tumor cells. It turns out that promoted • OH induction and intracellular calcium overload enable significant in vitro and in vivo antitumor phenomena., (© 2021 The Authors. Advanced Science published by Wiley-VCH GmbH.)

Traditional Fenton or Fenton-like oxidation has been widely studied for waste activated sludge dewaterability. However, the narrow pH range (2.0–4.0) and the instabilities of Fe2+ and H 2 O 2 have hindered its commercial application. Owing to the high alkalinity of anaerobic digestion (AD) sludge, traditional Fenton or Fenton-like oxidation is economically unfeasible for its dewatering. In this study, we successfully demonstrated a novel and feasible method that used nitrilotriacetic acid (NTA)-Fe0 combined with CaO 2 (NTA-Fe0/CaO 2) at near-neutral pH (∼6.0) (a slight pH adjustment) in which capillary suction time ratio (CST 0 /CST) and centrifuged weight reduction (CWR) improved by 6 folds and 42.98 ± 0.37%, respectively, under the optimal conditions. The presence of NTA accelerated the Fe0 corrosion, Fe2+ stability and turnover between Fe2+ and Fe3+. As such, Fe0 could effectively catalyze CaO 2 to produce hydroxyl radicals (•OH) under near-neutral conditions. Accordingly, various molecular weight hydrophilic compounds in different extracellular polymeric substances fractions were significantly reduced after treatment. The hydrophilic functional groups especially protein molecules were largely reduced. Consequently, the viscosity of sludge and particle size effectively decreased, while the release of bound water, surface charge, flocculation, and flowability of sludge were improved. The cost-benefit analysis further demonstrated the NTA-Fe0/CaO 2 treatment has high reusability and stability and is also more economical over the FeCl 3 /CaO and Fenton's reagent/CaO treatments. In summary, the NTA-Fe0/CaO 2 process is a cost-effective and practically feasible technology for improving AD sludge dewaterability. Image 1 • NTA hinders iron precipitation and captures Fe2+/Fe3+ in AD sludge dewatering. • •OH oxidation and iron flocculation act synergistically. • NTA-Fe0/CaO 2 effectively enhances AD sludge dewaterability at near-neutral pH. • Refractory and hydrophilic biopolymers in EPS are also degraded. [ABSTRACT FROM AUTHOR]

• CaO 2 /SAM-SS was successfully prepared for slow release and reaction of CaO 2. • CaO 2 /SAM-SS increased SCFAs production and prolonged the high concentration state. • Bacterial diversity and live/dead cell ratio were all reduced by CaO 2 /SAM-SS. • CaO 2 and SAM-SS in CaO 2 /SAM-SS had synergetic effects in •OH generation. In order to prolong the effect of CaO 2 on improvement of short-chain fatty acids (SCFAs) production in sludge anaerobic fermentation, CaO 2 particles were successfully loaded onto the porous surface of steel slag pre-modified with salicylic acid-methanol (SAM-SS). The prepared CaO 2 /SAM-SS was then characterized and investigated for its effects on anaerobic fermentation. Experimental results revealed that, due to the slow release and reaction of CaO 2 /SAM-SS, SCFAs concentrations in CaO 2 /SAM-SS tests were significantly higher than in the control and SAM-SS tests, and high SCFAs concentration was sustained for a longer period than in the CaO 2 tests. Since most bacterial indexes were reduced by CaO 2 /SAM-SS, more supply of "raw materials" from a better disintegration and hydrolysis, which was associated with the alkalinity and •OH radicals released from the reaction of CaO 2 with H 2 O, contribute to the higher SCFAs yields. This study provides a new approach towards a higher and longer SCFAs harvesting. [ABSTRACT FROM AUTHOR]

Combined chemo/chemodynamic therapy is a promising strategy to achieve an improved anticancer effect. However, the hypoxic microenvironment and limited amount of H2O2 in most solid tumors severely restrict the efficacy of this treatment. Herein, the construction of a nanocatalytic medicine, CaO2@DOX@ZIF‐67, via a bottom‐up approach is described. CaO2@DOX@ZIF‐67 simultaneously supplies O2 and H2O2 to achieve improved chemo/chemodynamic therapy. In the weakly acidic environment within tumors, CaO2@DOX@ZIF‐67 is broken down to rapidly release the Fenton‐like catalyst Co2+ and the chemotherapy drug doxorubicin (DOX). The unprotected CaO2 reacts with H2O to generate both O2 and H2O2. The generated O2 relieves the hypoxia in the tumor and further improve the efficacy of DOX. Meanwhile, the generated H2O2 reacts with Co2+ ions to produce highly toxic •OH through a Fenton‐like reaction, resulting in improved chemodynamic therapy. [ABSTRACT FROM AUTHOR]

• A novel laminated Fe 3 O 4 /CaO 2 composite was successfully prepared for As (III) removal. • Fe 3 O 4 /CaO 2 showed good oxidation and adsorption properties for As (Ⅲ), especially for ultratrace As (Ⅲ). • The inhibition effects of phosphate for As (Ⅲ) adsorption by Fe 3 O 4 /CaO 2 is much lower. In this study, for the first time, cheap CaO 2 was introduced to combine with Fe 3 O 4 nanoparticles by coprecipitation method to form multifunctional Fe 3 O 4 /CaO 2 composites for arsenite (As (Ⅲ)) oxidation and adsorption. A novel laminated Fe 3 O 4 /CaO 2 nanocomposite was obtained by varying the molar ratio of Fe 3 O 4 /Ca from 5:1 to 1:5. The laminated Fe 3 O 4 /CaO 2 showed good oxidation and adsorption properties for As (Ⅲ), especially for ultratrace As (Ⅲ) (< 40 ppb) treatment. As (III) concentration can be effectively controlled below the international requirement of 10 ppb, which may be due to the oxidation function of Fe 3 O 4 /CaO 2 since As (III) can be quickly oxidized into As (Ⅴ) within 15 min. The adsorption capacities of Fe 3 O 4 /CaO 2 (the molar ratio of Fe 3 O 4 /Ca is 1:5) was 56.35 mg g−1 when pH is 6 and the amount of Fe 3 O 4 /CaO 2 is 2 mg mL-1. Excitingly, the inhibition effects of phosphate for As (Ⅲ) adsorption by Fe 3 O 4 /CaO 2 is much lower than that of most of the other reported materials. These results suggest that Fe 3 O 4 /CaO 2 composite can be employed as a promising adsorbent to treat As (III), even in ultratrace concentration. [ABSTRACT FROM AUTHOR]

Combined chemo/chemodynamic therapy is a promising strategy to achieve an improved anticancer effect. However, the hypoxic microenvironment and limited amount of H 2 O 2 in most solid tumors severely restrict the efficacy of this treatment. Herein, the construction of a nanocatalytic medicine, CaO 2 @DOX@ZIF-67, via a bottom-up approach is described. CaO 2 @DOX@ZIF-67 simultaneously supplies O 2 and H 2 O 2 to achieve improved chemo/chemodynamic therapy. In the weakly acidic environment within tumors, CaO 2 @DOX@ZIF-67 is broken down to rapidly release the Fenton-like catalyst Co 2+ and the chemotherapy drug doxorubicin (DOX). The unprotected CaO 2 reacts with H 2 O to generate both O 2 and H 2 O 2 . The generated O 2 relieves the hypoxia in the tumor and further improve the efficacy of DOX. Meanwhile, the generated H 2 O 2 reacts with Co 2+ ions to produce highly toxic •OH through a Fenton-like reaction, resulting in improved chemodynamic therapy., Competing Interests: The authors declare no conflict of interest., (© 2019 The Authors. Published by WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim.)

Adsorption is an economical and effective method for recovering phosphate from wastewater. In order to improve the adsorption capacity of Fe 3 O 4 for phosphate and for easy separation from water under the action of an external magnetic field, CaO 2 was used in this study as an oxidant to partially oxidize Fe 2+ . A phosphorus recovery adsorbent, Ca doped Fe 3 O 4 (CMIO), was prepared and was characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF) and vibrating sample magnetometer (VSM) techniques. The results showed that CMIO had a Ca 2+ doped Fe 3 O 4 crystal structure with a saturation magnetization of 38.82 emu·g -1 , which was easily separated from water by using an external magnetic field. The phosphorus adsorption capacity of the CMIO decreased with an increase of pH value. When pH=2 and T =25℃, the maximum adsorption capacity was 24.10 mg·g -1 , which is almost five times the adsorption capacity of pure Fe 3 O 4 . The phosphorus adsorption of CMIO was in accord with the Langmuir isotherm adsorption model, and the adsorption process followed the pseudo-second order kinetic model. The complexation of phosphate occurred on the inner surface of the CMIO to form a ≡Fe-Ca-P ternary complex, which can adsorb phosphorus. Compared with other anions in the aqueous solution, CMIO had good adsorption selectivity to PO 4 3- , and the adsorbed PO 4 3- could be desorbed by NaOH solution.The quality loss of the CMIO was less than 4% once, and multiple recycling was possible.

Nano zerovalent iron (nZVI) and CaO 2 were used to construct a heterogeneous Fenton-like system to degrade α -hexachlorocyclohexane ( α -HCH) in soil solution, and the degradation efficiency and mechanism were investigated. The results showed that nZVI/CaO 2 can degrade α -HCH in an extensive pH range. When the dosage of nZVI and CaO 2 was 1 g·L -1 and pH was 5, the degradation rate of α -HCH reached 93.23%. The degradation process of nZVI, CaO 2 , and nZVI/CaO 2 treatments accorded with the first-order reaction kinetics model. The reaction rate constant of nZVI/CaO 2 was greater than the sum of individual treatments, showing that nZVI/CaO 2 has a synergistic effect on the degradation of α -HCH. Through quenching free radical experiments, the contribution rate of superoxide radicals was shown to be greater than that of hydroxyl radicals. Intermediates, including trichlorobenzene and chlorobenzene, were detected. The content of trichlorobenzene showed a sharp increase initially, and then decreased quickly. The chlorobenzene content was low and showed little change. The α -HCH in the soil washing solution was first reduced to trichlorobenzene, which was further reduced to chlorobenzene or mineralized into CO 2 and water directly.