Catalytic Degradation Of Tetracycline Research Articles

Novel durable and recyclable Cu@MoS2/polyacrylamide/copper alginate hydrogel photo-Fenton-like catalyst with enhanced and self-regenerable adsorption and degradation of high concentration tetracycline

A durable and recyclable Cu@MoS2/polyacrylamide/copper alginate nanocomposite double network (Cu@MoS2/PAAm/CA NCDN) hydrogel photo-Fenton-like catalyst was prepared for efficient removal of high concentration tetracycline (TC) in pharmaceutical wastewater. This hydrogel catalyst exhibits a remarkable synergistic effect between adsorption and catalytic degradation of TC. Consequently, this hydrogel catalyst shows a larger TC adsorption capacity of 122.2 mg g−1 and a higher TC degradation efficiency of 90% (degradation amount = 70.2 mg g−1) at the TC concentration of 200 mg L−1, while the TC degradation efficiency by Cu@MoS2 catalyst is only 19% (degradation amount = 38.2 mg g−1). This hydrogel catalyst can effectively remove high concentration TC under both light and dark conditions. Moreover, the tensile strength of Cu@MoS2/PAAm/CA NCDN hydrogel catalyst reaches an extraordinary 1.46 MPa and maintains 0.68 MPa after 15-day immersion in water, indicating high durability. In addition, the flexible hydrogel catalyst can keep good integrity after being deformed by stretching, bending, and knotting, etc., enabling its easy recovery. This investigation provides an innovative and versatile strategy to develop high-performance hydrogel catalysts for treating antibiotics-polluted water.

Cysteine and Ionic Liquid Modified Magnetic Nanoparticles Supported RuCu as a New Bimetallic Catalyst in Reduction Reactions

In this study, bimetallic RuCu supported on L-cysteine functionalized ionic liquid modified magnetic nanoparticles (Fe3O4@IL-Cys-RuCu) was successfully synthesized and characterized. This bimetallic nanocatalyst showed excellent activity in the reduction of 2,3, and 4-nitrophenol isomers and organic dyes as well as catalytic degradation of tetracycline (TC) at room temperature in water. Using this catalyst, complete reduction of nitrophenols was achieved within 9-16 min and degradation of organic dyes and tetracycline were accomplished within 7-4 and 30 minutes, respectively. The superior activity of bimetallic RuCu compared to similar Ru and Cu catalysts was proved and results indicated that the based on type of reaction, bimetallic catalyst was 2-33 times more efficient than the corresponding monometallic catalysts. This catalyst was recovered and recycled up to 14 times without decreasing in the catalytic activity and stability of the reused catalyst was confirmed by TEM, XRD and XPS.

Catalytic degradation of tetracycline using marigold flower-like structure erbium molybdate decorated on sulphur-doped g-C3N4 nanocomposite: Kinetics, thermodynamics, DFT calculations, and toxicity studies

In this study, a novel nanocomposite has been developed comprising erbium molybdate decorated on sulphur-doped graphitic carbon nitride (EMO/SGCN) acts as an effective catalyst for the degradation of tetracycline (TC) by NaBH4. The as-prepared catalyst exhibited remarkable catalytic behavior towards the removal of TC, with degradation efficiency and rate constants (k) of 89.15% and 0.0576 min−1, respectively, during the first 90 min. The TC degradation kinetics followed a pseudo-first order response based on the correlation coefficient (R2) values and adsorption capabilities. Catalytic degradation routes were spotted by GC-MS (Gas chromatography-mass spectrometry) analysis. The degradation mechanism of TC by the catalyst was suggested grounded on the experimental investigation and density functional theory calculations. Toxicity prediction was used to assess the toxicity of intermediates. Therefore, the use of EMO/SGCN in the presence of NaBH4 for the catalytic degradation of antibiotics in wastewater treatment can provide new insights into metal composite-based catalysts.

Heterogeneous photo-Fenton catalyst α-Fe2O3@g-C3N4@NH2-MIL-101(Fe) with dual Z-Scheme heterojunction for degradation of tetracycline

A novel photo-Fenton catalyst α-Fe2O3@g-C3N4@NH2-MIL-101(Fe) (FGN) with dual Z-scheme heterojunction was successfully prepared by hydrothermal method to degrade tetracycline (TC). The preparation conditions were optimized by orthogonal test, and the successful synthesis was confirmed by characterization analyses. The prepared FGN showed better light absorption performance, higher photoelectrons-holes separation efficiency, lower photoelectrons transfer resistance, and higher specific surface area and pore capacity compared with α-Fe2O3@g-C3N4 and α-Fe2O3. The effects of experimental conditions on the catalytic degradation of TC were investigated. The degradation rate of 10 mg/L TC could reach 98.33% within 2 h when the dosage of FGN was 200 mg/L, and the degradation rate could remain 92.27% after 5 times of reuse. Furthermore, the XRD spectra and XPS spectra of FGN before and after reuse were compared to explore the structural stability and catalytic active sites of FGN, respectively. According to the identification of oxidation intermediates, three degradation pathways of TC were proposed. Through H2O2 consumption experiment, radical-scavenging experiments, EPR results, the mechanism of the dual Z-scheme heterojunction was proved. The improved performance of FGN was attributed to the dual Z-Scheme heterojunction effectively promoting the separation of photogenerated electrons from the holes and accelerating the electrons transfer, and the increase of the specific surface area.

Magnetic biochar based on platanus leaves and iron sludge for persulfate activation and catalytic degradation of tetracycline

In this study, a novel magnetic biochar (BC-Fen), synthesized by one-step pyrolysis at 800 °C using platanus leaves and iron-containing sludge in different mass ratios, was used to activate persulfate (PS) for tetracycline (TC) degradation. Results show that BC-Fe1:2 exhibited excellent degradation performance (91.4%), much better than the raw biochar (BC) (77.1%). And electron paramagnetic resonance (EPR) techniques demonstrated radical (SO4·−, ·OH, O2·−) and non-radical (1O2) pathways in BC-Fe1:2/PS, S O4·− was further proved to be the main active species by quenching experiments. Liquid chromatography-mass spectrometry (LC-MS) was utilized to identify the intermediates of TC and three possible degradation pathways were proposed. Additionally, the BC-Fe1:2 was weakly affected by pH and the coexisting anions in wastewater, and could still remove 80% of TC in the third cycle experiment. This study provides a new idea for converting backwash iron-containing sludge from groundwater treatment plants into valuable catalysts, and provides new insights into the key role of low-cost magnetic biochar in PS activation.

Enhanced electro-Fenton degradation of tetracycline in aqueous solution using a self-supported BiOCl/CF cathode.

The cathode material is critical to the yield of hydrogen peroxide (H2O2) and electro-Fenton (EF) performance. In this work, bismuth oxychloride (BiOCl) as one of the representatives of ternary oxides was grown in situ on carbon felt (CF) through a simple solvothermal method and employed directly as a self-standing cathode for the EF degradation of the target contaminant tetracycline (TC). TC can be almost completely degraded, up to 95% in 90 min under the heterogeneous EF process. The characterizations demonstrated that the BiOCl/CF electrode exhibited excellent conductivity due to CF as the supporting carbon material with a 3D network structure; meanwhile, this hybrid electrode also possessed abundant active sites attributed to the decorated BiOCl having rich oxygen defects. Finally, the rational reaction mechanism of TC was also elucidated by the X-ray photoelectron spectroscopy (XPS) spectrum, free radical quenching experiments and electron paramagnetic resonance (EPR) spectra, in which hydroxyl radicals (ċ OH) were considered as the dominant active oxidants and BiOCl had a synergistic effect on in-situ generation and decomposition of H2O2.

Coupling humic acid in Fe-bearing montmorillonite for enhanced adsorption and catalytic degradation of tetracycline.

Clay-based materials have attracted attention owing to their dual effects of adsorption and advanced oxidation degradation in removing organic pollutants. In this study, the introduction of humic acid (HA) in the Fe-bearing montmorillonite (Fe-Mt) nano platform enhanced its tetracycline (TC) adsorption and degradation were investigated. The result showed that the adsorption and degradation efficiency of humic acid/poly-hydroxyl-iron/montmorillonite (HA-Fe-Mt) was greater than those of Fe-Mt. The adsorption performance and characterization confirmed that HA-Fe-Mt had more functional groups, stronger hydrophobic character, and higher specific surface area. The introduction of HA onto the Fe-Mt platform enhanced its specific surface area, electrostatic interaction, and hydrophobic character, therefore providing more active sites to interact with the carbonyl and amide groups of TC. Moreover, the catalytic performance and characterization results revealed that HA-Fe-Mt had greater persulfate (PS) activation, the coupled HA would speed up the transmission of electrons between Fe (III) and PS in the Fe (III) / Fe (II) cycle when PS was captured by the HA-Fe-Mt system, and the in situ generated Fe accelerates the generation of reactive oxygen species (ROS) to further degrade TC. Consequently, HA can not only promote the adsorption of TC but also promote the degradation of TC in the Fe-Mt nano platform. HA-Fe-Mt provided a feasible and promising platform with PS activation for TC adsorption and degradation.

“Two-in-one” sulfur and nitrogen co-doped fluorescent silicon nanoparticles: Simultaneous as the fluorescent probe and photocatalyst for in-situ real time visual monitoring and degradation of tetracycline antibiotics

Detection and removal of contaminants are significant for environmental monitoring and remediation. In the present study, “two-in-one” silicon nanoparticles (SiNPs) were designed and prepared to simultaneously act as the fluorescent probe and degradation catalyst to detect and remove tetracycline (TCs) antibiotics. Thiourea and 3-aminopropyltrimethoxysilane were dopant and silicon source to generate fluorescent sulfur and nitrogen co-doped SiNPs (SN-SiNPs). The blue fluorescence of SN-SiNPs was selectively quenched by TCs due to the inner filter effect, whilst accompanied by the newly appeared yellow-green fluorescence resulting from aggregation induced fluorescence emission effect. Based on this phenomenon, SN-SiNPs can be used as fluorescent colorimetric probes for detection of doxycycline, oxytetracycline and tetracycline with limits of detection of 1.8 μg/L, 3.0 μg/L and 4.2 μg/L, respectively; the semi-quantitation can even be visually achieved by naked eyes. Particularly, SN-SiNPs were capable to catalyze the degradation of the three TCs effectively, achieving the removal rates of doxycycline, oxytetracycline and tetracycline of >90 %, >80 % and > 70 % after 240 min exposure to UV light. The catalytic ability of SN-SiNPs was derived from hydroxyl radical (•OH−), superoxide radical (•O2−) and singlet oxygen (1O2) produced by SN-SiNPs under UV irradiation. Moreover, integrating the fluorescent probe and photocatalyst together, the proposed SN-SiNPs simultaneously realized catalyzing the degradation of the three TCs and in-situ visually monitoring of the degradation process in real time. This study innovatively proposed an integrated probe for the detection and catalytic degradation of TCs, providing a new “two-in-one” strategy for rapid and simple detection and removal of drug pollutants.

Effective degradation of tetracycline via recyclable cellulose nanofibrils/polyvinyl alcohol/Fe3O4 hybrid hydrogel as a photo-Fenton catalyst

In this work, the method of in-situ co-precipitation was used to prepare PVA/CNF/Fe3O4 hybrid hydrogel, and the relationship between its structure and performance was explored. The Fe3O4NPs prepared by this method were dispersed on the carrier PVA/CNF hydrogel and were easy to recover. The catalytic degradation of tetracycline was investigated using PVA/CNF/Fe3O4 hybrid hydrogel as photo-Fenton catalysts. The results showed that light and hydrogel carriers were pivotal factors in promoting Fe2+ and Fe3+ cycling and that the PVA/CNF/Fe3O4 hybrid hydrogel as catalysts were able to activate H2O2 to generate a large amount of oxygen radical •OH, resulting in efficient removal of tetracycline. The tetracycline degradation followed a proposed first-order kinetic model and achieved a removal rate of about 98% in 120 min at an optimum pH of 3, H2O2 100 mM, catalyst 0.3 g/L, and a temperature of 25 °C.

A comparative study on adsorption and catalytic degradation of tetracycline by five magnetic mineral functional materials prepared from steel pickling waste liquor

Palygorskite (Pal), bentonite (Bent), sepiolite (Sep), zeolite (Zeol), and kaolin (Kaol) were used with steel pickling waste liquor to synthesize magnetic palygorskite (Pal@Fe3O4), magnetic bentonite (Bent@Fe3O4), magnetic sepiolite (Sep@Fe3O4), magnetic zeolite (Zeol@Fe3O4), and magnetic kaolin (Kaol@Fe3O4), for adsorption and catalytic degradation of tetracycline (TC), respectively. Through the study of adsorption kinetics and adsorption isotherms, the maximum adsorption capacity of Pal@Fe3O4 to TC was 149.439mg/g, which was 1.239 times, 2.260 times, 3.161 times, and 3.448 times of Bent@Fe3O4, Zeol@Fe3O4, Kaol@Fe3O4, and Sep@Fe3O4, respectively. The kinetic study of tetracycline degradation demonstrated that the maximum reaction rate constant of Bent@Fe3O4/H2O2 system was K(obs) = 2.12 × 10-2min-1, which was close to that of Pal@Fe3O4/H2O2, Kaol@Fe3O4/H2O2 system, and was 2.000 times, 2.356 times, 2.650 times, and 4.711 times of Fe3O4/H2O2, Zeol@Fe3O4/H2O2, Sep@Fe3O4/H2O2, and H2O2 system, respectively. The results showed that Pal@Fe3O4 and Bent@Fe3O4 were more advantageous in the treatment of wastewater containing tetracycline, and efficient reuse of exhausted magnetic minerals and deep mineralization of organic pollutants were achieved by constructing an advanced oxidation system. The BET, VSM, SEM, XPS, XRD, and FTIR were used to characterize the five clay minerals before and after magnetic modification. It was speculated that the surface structure - OH groups of clay minerals might be significant factors influencing the adsorption performance of magnetic minerals on TC, and reduction ability of clay minerals to Fe3+ importantly affected the catalytic performance of magnetic minerals. The specific surface area and morphological structure of clay minerals both affected the adsorption and catalytic degradation of TC by the five magnetic minerals.

Facile fabrication of LaFeO3/zeolite composite for degradation of tetracycline with enhanced photo‐Fenton catalytic activity under visible light

AbstractLaFeO3/zeolite (LFO‐Z) composite has been successfully synthesized via impregnation‐calcination method for the photo‐Fenton degradation of Tetracycline (TC). The incorporation of LaFeO3 particles on zeolite support contributes to the enhancement in photo‐Fenton catalytic activity of LFO‐Z photocatalyst by increasing the contact area between the material and TC molecules. The LFO‐Z photocatalyst was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD), N2 adsorption‐desorption, and optical absorption spectra. Different operational parameters such as catalyst dosage, H2O2 concentration, pH was investigated in the photo‐Fenton catalytic degradation of TC. 76.4 % of TC was degraded after 150 min exposure to visible light under the conditions of 1 g L‐1 LFO‐Z, 10 mg L‐1 TC, 10 mM H2O2 and pH of 6. The LFO‐Z composite shows a high stability and reusability, suggesting its potential use as a photocatalyst for pharmaceutical degradation via the photo‐Fenton process.

Catalytic degradation of tetracycline using peroxymonosulfate activated by cobalt and iron co-loaded pomelo peel biochar nanocomposite: Characterization, performance and reaction mechanism

Tetracycline (TC) is a refractory pollutant that widely exists in water environments. Therefore, effective TC treatment methods must be developed. In this work, a cobalt and iron coloaded pomelo peel biochar composite (Co-Fe@PPBC) was successfully synthesized and used to activate peroxymonosulfate (PMS) for TC removal. The crystal structure, surface morphology, pore structure, and elemental valence of the synthesized Co-Fe@PPBC catalyst were investigated by BET, SEM, XRD, FTIR, XPS, TGA, Raman, and VSM. The effects of Co-Fe@PPBC dosage, PMS concentration, initial pH, initial TC concentration, and coexisting anions on TC removal were studied. In comparison with the oxidation (13.6%) by PMS alone and adsorption (9.6%) by Co-Fe@PPBC alone, the removal efficiency of TC was increased to 86.2% in the Co-Fe@PPBC/PMS system, indicating that Co-Fe@PPBC can successfully activate PMS. Remarkably, the results of scavenging examination and EPR analysis demonstrated the synergistic effect of free radical and non-free radical pathways in TC degradation. The cycling test showed that Co-Fe@PPBC has favourable stability and recyclability during repeated activation processes of PMS. Finally, three possible TC degradation methods were presented through the analysis of eight intermediates. Overall, Co-Fe@PPBC could be an economic and high-efficiency catalyst for PMS activation to remove organic pollutants in wastewater.

Magnetic Cufe2o4/ Zeolitic Imidazolate Frameworks for Catalytic Degradation of Tetracycline, Reduction of 4-Nitrophenol and Organic Dyes

Magnetic Cufe2o4/ Zeolitic Imidazolate Frameworks for Catalytic Degradation of Tetracycline, Reduction of 4-Nitrophenol and Organic Dyes

Polyoxometalate intercalated La-doped NiFe-LDH for efficient removal of tetracycline via peroxymonosulfate activation

• La-doped NiFe-LDH containing Keggin type polyoxometalate interlayer were synthesized. • The NiFeLa{HPW}-LDH exhibited better catalytic performance than NiFeLa-LDH. • The intercalated HPW played a vital role in electron transfer. • SO 4 − and OH were the main radicals in catalytic degradation of tetracycline. • The formation of the complex and redox cycle were responsible for the catalysis. In this work, a series of La-doped NiFe-layered double hydroxides containing a novel Keggin type polyoxometalate interlayer (NiFeLa{HPW}-LDH) were synthesized and initially applied as heterogeneous catalyst for peroxymonosulfate (PMS) activation. Characterizations indicated that polyoxometalate anions were successfully intercalated in the layers of NiFeLa-LDH. Experiment results showed that NiFeLa{HPW}-LDH exhibited better catalytic performance than the counterpart precursor. The influences of various experimental parameters, such as pH value, initial TC concentration, HPW intercalation content, catalyst loading and peroxymonosulfate concentration were investigated in detail. Quenching experiments and the results of electron paramagnetic resonance (EPR) demonstrated the SO 4 − and HO were the dominant reactive radicals engaging in the degradation process. Furthermore, the formation of a complex of Ni(II)/Fe(II)/La(III)−(HO)OSO 3 − and the succeeding redox cycle of Ni(II)/Ni(III)/Ni(II), Fe(II)/Fe(III)/Fe(II), La(III)/La(IV)/La(III) were responsible for the generation of active radicals via activating PMS. Meanwhile, it's worth noting that the intercalated HPW also played a vital role in electron transfer.

Activation of peroxymonosulfate using metal-free in situ N-doped carbonized polypyrrole: A non-radical process

Metal-free catalysts are widely considered as promising alternatives to traditional metal-based catalysts, which can effectively activate peroxymonosulfate (PMS). In this study, a novel metal-free catalyst, carbonized polypyrrole (CPPy) was synthesized through high-temperature carbonization of PPy, easily achieving the in situ N doping without the addition of nitrogen sources. Tetracycline (TC) was selected as the target contaminant to assess the catalytic activity of the CPPy/PMS system. Enhanced catalytic activity was observed in CPPy/PMS over a wide pH range (3.0–9.0), and the removal rate of TC by CPPy-3/PMS reached 91.3% after 10 min. After regenerating the used catalyst, the catalytic activity was refreshed, implying its stability and recyclability. The catalytic degradation of TC by CPPy/PMS was mainly attributed to a non-radical process. CPPy, as an intermediary, grabbed electrons from the electron-donating groups of TC and transferred them to the PMS molecule. Thereafter, TC that lost electrons was oxidized and degraded, and the O–O bonds of PMS were destroyed by the transferred electrons to form SO42− and OH−. Moreover, O⋅2− and 1O2 were involved in TC degradation. TC degradation pathway was investigated through HPLC-MS analysis. These findings provide a promising strategy for the construction of catalysts for PMS and environmental remediation.

Facet-controlled activation of persulfate by magnetite nanoparticles for the degradation of tetracycline

Three kinds of magnetite nanoparticles (MNPs) with different exposed crystal facets were synthesized by hydrothermal methods to investigate the effects of exposed facets on the catalytic performance. Under the heterogeneous activation of persulfate (PS), MNPs exposed with {111} facet exhibited better catalytic performance than that exposed with {110} or {100} facet in the degradation of tetracycline, and catalytic performance followed the order of MNPs{111} > MNPs{100} > MNPs{110}. The degradation efficiency of PS/MNPs{111} system reached 74.38% in 4 h, which was much higher than PS/MNPs{110} (19.29%) or PS/MNPs{100} (33.79%) system. Hydroxide, physically adsorbed H2O on the MNPs surface and transformations of Fe(II)/Fe(III) were the main factors to determine the high catalytic performance of MNPs{111} for PS, as illustrated by the X-ray photoelectron spectroscopy (XPS) analysis. The corresponding catalytic oxidation mechanism has been proposed on the basis of attenuated total reflection flourier transformed infrared spectroscopy (ATR-FTIR), electron paramagnetic resonance (EPR) spectroscopy and quenching tests. SO4− and OH were the main radicals in catalytic degradation of tetracycline. Density functional theory (DFT) analysis suggested that the difference of {110}, {111} and {100} facets of magnetite determine the electron density and the density of states on the surface of catalysts. In addition, relatively low concentration of humic acid promoted the removal of tetracycline, and higher concentration of humic acid inhibited the tetracycline removal.

Novel NiFe2O4 deposited S-doped g-C3N4 nanorod: Visible-light-driven heterojunction for photo-Fenton like tetracycline degradation

Fabrication of visible-light-active heterojunction photocatalysts for organic pollutant degradation plays a crucial role in the environmental remediation field. We have fabricated sulfur-doped carbon nitride nanorod (SCNNR) by template free urea assisted hydrothermal method. The facile wet chemical impregnation method was used to deposit nickel ferrite (NFO) nanoparticles on the SCNNR. Various analytical characterization methods were used to study the structural, morphological, optical, and chemical compositions of the prepared photocatalysts. Strong chemical interaction between the NFO and SCNNR nanoparticles enhances the visible-light utilization and also improves the suppression of electron-hole recombination. In particular, the composite 20NFO/SCNNR photocatalyst exhibits greater photo-Fenton-like catalytic degradation of tetracycline (TCN) in the presence of H2O2 under commercial LED light irradiation. The photo-Fenton reaction mechanism and reactive oxygen species for TCN degradation were investigated by the elemental trapping experiment. Moreover, the recycle test proves that the prepared composite photocatalyst is an efficient candidate for environmental remediation applications.

Metal-organic framework modified pine needle-derived N, O-doped magnetic porous carbon embedded with Au nanoparticles for adsorption and catalytic degradation of tetracycline

Pine needles (PNs) were used as a biomass precursor to fabricate N, O-doped magnetic porous carbon frameworks (PN−MPC) after modification with metal-organic frameworks (MOFs) and carbonization. And PN−MPC catalysts embedded with Au nanoparticles (Au/PN−MPC) were fabricated by a facile two-step route involving impregnation and subsequent thermal reduction procedures. The crystal structures, morphologies, chemical component, and microstructure of the Au/PN−MPC catalysts were initially investigated through various physicochemical characterization. Au/PN−MPC900 exhibited outstanding catalytic activity toward tetracycline (TC) degradation in the presence of H2O2, with a degradation efficiency and degradation rate constant of 96% and 0.133 min−1 within initial 10 min, respectively. The effects of operating parameters, including initial pH, temperature, catalyst dosage, initial concentrations of TC, and H2O2 concentration on TC degradation were comprehensively investigated. The superior mineralization performance and pH tolerance abilities and catalytic stability of Au/PN−MPC900 were also discussed. After seven consecutive cycles, the removal efficiency of Au/PN−MPC900 for TC degradation was not only greater than 82%, but also exhibited excellent reusability performance. Furthermore, ·OH radicals were confirmed as the dominant reactive species roles for the degradation of antibiotic pollutants through EPR and ·OH−trapping fluorescence spectral tests, and a plausible catalytic degradation mechanism was proposed. Correspondingly, several possible degradation pathways of TC were tentatively proposed on the basis of the degradation intermediates identified by HPLC-MS measurements. Overall, this novel biomass-derived magnetic porous carbon material embedded with Au nanoparticles is highly promising for many applications, especially in the field of environmental remediation.

Tetracycline removal from aqueous solution by visible-light-driven photocatalytic degradation with low cost red mud wastes

Antibiotics wastewater poses a major threat to the global environment and human health. In this work, red mud (RM) and modified RM (after calcination treatment), as industrial solid wastes discharged from the aluminum industry, were used as effective photocatalysts for removal of tetracycline (TC) from water under visible light irradiation. The results showed that the photocatalytic degradation activity of modified RM on TC was obviously better than that of original RM (RM-raw). Furthermore, RM-350 (calcination temperature is 350 °C) exhibits the best photocatalytic performance (100 mL, 10 mg/L; 88.4% degradation of TC within 80 min) under visible light as well as outstanding stability after three reaction cycles. The improvement in photocatalytic performance by modified RM is mainly due to an increase in specific surface area and crystallinity, which is benefit for promoting adsorption of organic pollutants and accelerating photo-induced charges. The effects of catalyst dosage and initial concentration on the catalytic degradation of TC were studied. Our work has proved that RM is a novel low-cost photocatalyst, which not only provides a useful solution for the reuse of RM, but also plays an important role in environmental protection.

Bi2Zr2O7 nanoparticles synthesized by soft-templated sol-gel methods for visible-light-driven catalytic degradation of tetracycline

Tetracycline (TC), an antibiotic, is persistent in nature and frequently detected in water and sediments. Visible-light-driven photocatalyst for TC degradation is a promising environmental-friendly technology. Bi2Zr2O7, an effective photocatalyst, but no studies on its photodegradation of TC could be found in literature. In this study, Bi2Zr2O7 was synthesized by three soft templated sol-gel methods. Three synthesized Bi2Zr2O7 catalysts have different structures, morphologies and band gaps. The Bi2Zr2O7 nanoparticles synthesized with citric acid as the template (BZO-3) had a larger specific surface area (30.7 m2/g) and a narrower band gap (2.39 eV), and exhibited a better performance for TC degradation under visible light with an efficiency of up to 81.3%. They also exhibited good stability and reusability in recycled experiments. A reaction mechanism of TC degradation by these photocatalyst was proposed. The enhanced photocatalytic performance was mainly due to photogenerated holes of reactive species and TC was mainly degraded on the surface of the photocatalyst. Pathways of TC photodegradation were derived from the result of analyses of the reaction intermediates. In conclusion, Bi2Zr2O7 nanoparticles were found effective as photocatalyst for TC photodegradation by visible light.