Tc Removal Research Articles

Enhanced Tetracycline Removal from Highly Concentrated Aqueous Media by Lipid-Free Chlorella sp. Biomass.

Microalgae are used as a lipid source for different applications, such as cosmetics and biofuel. The nonliving biomass and the byproduct from the lipid extraction procedure can efficiently remove antibiotics. This work has explored the potential use of Chlorella sp. biomasses for tetracycline (Tc) removal from highly concentrated aqueous media. Non-living biomass (NLB) is the biomass before the lipid extraction procedure, while lipid-extracted biomass (LEB) is the byproduct mentioned before. LEB removed 76.9% of Tc at 40 mg/L initial concentration and 40 mg of biomass, representing an adsorption capacity of 19.2 mg/g. Subsequently, NLB removed 68.0% of Tc at 50 mg/L and 60 mg of biomass, equivalent to 14.2 mg/g of adsorptive capacity. These results revealed an enhanced removal capacity by LEB compared with NLB and other microalgae-based materials. On the other hand, the adsorption kinetics followed the pseudo-second-order and Elovich models, suggesting chemisorption with interactions between adsorbates. The adsorption isotherms indicate a multilayer mechanism on a heterogeneous surface. Additionally, the interactions between the surface and the first layer of tetracycline are weak, and the formation of the subsequent layers is favored. The Chlorella sp. biomass after the lipid extraction process is a promising material for removing tetracycline; moreover, the use of this residue contributes to the zero-waste strategy.

Preparation of BiFeO3 and photodegradation of tetracycline pollutant in the UV-heterogeneous Fenton-like system.

Surplus tetracycline in the water body causes damage to the ecology balance and human health. Therefore, this work established an efficient strategy, namely, the BFO-based UV-heterogeneous Fenton-like system, to eliminate TC pollution. The photocatalytic oxidation system has been integrated with the heterogeneous Fenton-like system, cooperated with the photolysis of H2O2. These synergistic effects could boost the generation of reactive species for the TC degradation and mineralization, due to the reduction of Fe(III) to Fe(II) by photogenerated electrons and the separation of photogenerated electron-hole pairs. The prepared BFO was stable with no secondary pollution, and could be recovered by an extra magnet to reuse. Compared with other single oxidation systems, this coupled system showed an outstanding performance in TC disposal, and TC and TOC removal efficiencies could reach 100% and 74.92%, respectively. Moreover, the mechanisms for TC degradation involved that TC was degraded by oxidation species, such as superoxide radicals, hydroxyl radicals, and positive holes, and intermediate products in the TC degradation process mainly were products at m/z = 459, m/z = 445, and m/z = 134. The promising TC disposal efficiency achieved by the integration between BFO-based photocatalytic and heterogeneous Fenton-like system sheds light on applying BFO to control water pollution.

Process optimization of high machining efficiency and low surface defects for HSD milling UD-CF/PEEK with limited thermal effect

Carbon fiber reinforced polyetheretherketone (CF/PEEK) is widely applied in aerospace and medical fields due to its excellent strength-to-weight ratio, fatigue resistance and biocompatibility. However, traditional dry machining significantly limits the improvement of machining efficiency and surface quality. Addressing this issue, this paper proposes a process optimization method of high machining efficiency and low surface defects for high-speed dry (HSD) milling UD-CF/PEEK, based on analyzing the thermal effect of cutting temperature. Mixed-level orthogonal experiments are designed for dry milling unidirectional (UD) CF/PEEK laminates with the fiber orientation of 0° and 90°. Three-dimensional surface roughness Sq, cutting temperature Tc and material removal rate MRR are extracted to characterize experiment results. The results show that the cutting temperature is mainly affected by cutting speed and fiber orientation, and machined surface defect is mainly caused by the thermal effect of high cutting temperature. Then, a process optimization model of high machining efficiency and low surface defects is established based on the genetic algorithm optimized BP (GA-BP) neural network, non-dominated sorting genetic algorithm (NSGA-II) and technique for order preference by similarity to an ideal solution (TOPSIS). The optimization objectives are Sq, MRR and Tc, and Tc also serves as a constraint of the thermal effect. Verification experiments are carried out, and results reveal that the surface defects are significantly reduced by limited thermal effect, and the model can be used to effectively improve machining efficiency and surface quality for HSD milling UD-CF/PEEK. Besides, the material removal rate generated by the HSD milling operation can easily reach 2–3 times higher than the traditional low-speed dry milling operation. The optimized cutting speed in HSD milling UD-CF/PEEK is recommended as 1300–1600 m/min. This study provides significant technical guidance for the machinability improvement of HSD milling UD-CF/PEEK in practice.

Enhanced catalytic activation of H2O2 by CNTs/SCH through rapid Fe(III)/Fe(II) redox couple circulation: Insights into the role of functionalized multiwalled CNTs

How to achieve the efficient generation of Fe(II) from Fe(III) in Fenton reaction is a significant issue. In this work, a novel composite of oxidized multiwalled carbon nanotubes - Schwertmannite (CNTs-SCH) were successfully synthesized through a coprecipitation and hydrothermal strategy. The results indicated that the prepared 15%CNTs-SCH would exhibit an excellent catalytic performance in activation of hydrogen peroxide for degradation of tetracycline. The Fe(III)/Fe(II) redox couple circulation would be greatly enhanced from dynamic and thermodynamic aspects. The sulfate radicals generating from SO42− on the surface of Schwertmannite would contribute to TC degradation, which was in line with the enhanced generation rate of Fe(II) and hydroxyl radical in the 15%CNTs-SCH system. In addition, C = C and C = O (in CNTs) were acting as key active sites in prompting formation of Fe(II) and hydroxyl radical. What’s more, the effects of pH, CNTs-SCH, hydrogen peroxide dosages, and common anions on TC removal were assessed. This investigation showed that the prepared 15%CNTs-SCH was an effective catalyst for hydrogen peroxide activation in the heterogeneous system with a wide pH range and good recyclability, confirming its stronger potential practical application.

Degradation of tetracycline hydrochloride through efficient peroxymonosulfate activation by B, N co-doped porous carbon materials derived from metal-organic frameworks: Nonradical pathway mechanism

• B, N co-doped carbon porous material was derived from metal-organic frameworks. • B-NC shows excellent performance in PMS activation and TC removal. • Singlet oxygen ( 1 O 2 ) was the domain active species in B-NC/PMS system. • Electron transfer was another non-radical oxidation pathway of B-NC/PMS system. • B-NC catalyst has relatively good stability for PMS activation. Peroxymonosulfate (PMS) based advanced oxidation process has been proved to be an efficient method for Antibiotic treatment. B, N co-doped carbon porous material was derived from metal-organic frameworks. B-NC catalysts showed excellent efficiency for removal of tetracycline hydrochloride. Nitrogen doping essentially changed the degradation pathway of tetracycline hydrochloride, while boron doping provided more active sites. through more defect sites, which is closely related to the adsorption and catalytic performance of the catalyst. The major active species of B-NC/PMS system was singlet oxygen ( 1 O 2 ) through quenching experiments and electron paramagnetic resonance (EPR) studies. Electron transfer was another non-radical oxidation pathway of B-NC/PMS system. This provides a new idea for the selective oxidation of antibiotics by metal-free activated PMS.

Simultaneous photocatalytic tetracycline oxidation and chromate reduction via a jointed synchronous pathway upon Z-scheme Bi12O17Cl2/AgBr: insight into intermediates and mechanism

A 2D/0D Bi12O17Cl2/AgBr Z-scheme photocatalyst provides a jointed synchronous pathway for simultaneous Cr(vi) and TC removal.

Biogeochemical Cycling of 99Tc in Alkaline Sediments.

99Tc will be present in significant quantities in radioactive wastes including intermediate-level waste (ILW). The internationally favored concept for disposing of higher activity radioactive wastes including ILW is via deep geological disposal in an underground engineered facility located ∼200-1000 m deep. Typically, in the deep geological disposal environment, the subsurface will be saturated, cement will be used extensively as an engineering material, and iron will be ubiquitous. This means that understanding Tc biogeochemistry in high pH, cementitious environments is important to underpin safety case development. Here, alkaline sediment microcosms (pH 10) were incubated under anoxic conditions under "no added Fe(III)" and "with added Fe(III)" conditions (added as ferrihydrite) at three Tc concentrations (10-11, 10-6, and 10-4 mol L-1). In the 10-6 mol L-1 Tc experiments with no added Fe(III), ∼35% Tc(VII) removal occurred during bioreduction. Solvent extraction of the residual solution phase indicated that ∼75% of Tc was present as Tc(IV), potentially as colloids. In both biologically active and sterile control experiments with added Fe(III), Fe(II) formed during bioreduction and >90% Tc was removed from the solution, most likely due to abiotic reduction mediated by Fe(II). X-ray absorption spectroscopy (XAS) showed that in bioreduced sediments, Tc was present as hydrous TcO2-like phases, with some evidence for an Fe association. When reduced sediments with added Fe(III) were air oxidized, there was a significant loss of Fe(II) over 1 month (∼50%), yet this was coupled to only modest Tc remobilization (∼25%). Here, XAS analysis suggested that with air oxidation, partial incorporation of Tc(IV) into newly forming Fe oxyhydr(oxide) minerals may be occurring. These data suggest that in Fe-rich, alkaline environments, biologically mediated processes may limit Tc mobility.

Metallic technetium sequestration in nickel core/shell microstructure during Fe(OH)2 transformation with Ni doping

This study investigates the impacts of Ni doping on technetium-99 (Tc) sequestration in aqueous solutions through transformation of Fe(OH)2(s) to iron spinel (magnetite) under alkaline conditions. Extensive solid characterization was performed for the mineral phases produced, as well as the Tc/Ni speciation and distribution within these phases. X-ray diffraction results show that iron spinel was the dominant mineral product without detectable Ni incorporation. The doped Ni ions mainly precipitated as fine Fe/Ni oxide/hydroxide particles, including strongly reduced nanometer˗sized spheroidal Ni-rich and metallic Ni phases. High-resolution analytical scanning transmission electron microscopy using energy dispersive X-ray spectroscopy and electron energy loss spectroscopy on the produced solid samples (focused ion beam-prepared specimens) revealed three Tc distribution domains dominated by nanocrystals and, especially, a Tc-rich metallic phase. Instances of metallic Tc were specifically found in spheroidal, Ni-rich and metallic nanoparticles exhibiting a core/shell microstructure that suggests strong reduction and sequential precipitation of Ni-Tc-Ni. Mass balance analysis showed nearly 100% Tc removal from the 4.8 × 10−4 M Tc solutions. The finding of the metallic Tc encapsulation indicates that Tc sequestration through Ni-doped Fe(OH)2(s)˗to˗iron spinel transformation process likely provides an alternative treatment pathway for Tc removal and could be combined into further waste treatment approaches.

Degradation of tetracycline using nanoparticles of zero-valent iron and copper

Abstract Tetracycline (TC) is one of the most persistent pharmaceuticals in the ecosystem. Advanced oxidation processes (AOPs) are suitable and effective technology for treating wastewater contaminated with antibiotics such as TC. In this manner, Fenton-like reaction is effective for wastewater treatment from toxicity and non-biodegradable organic pollutants using bimetallic nanoparticles. This study aims to verify the effect of AOPs using ZVI/Cu bimetallic nanoparticles on removing the TC antibiotic via a Fenton-like reaction, and what is necessary to evaluate the factors that influence the reaction, i.e. pH, ZVI/Cu dose, stirring intensity, H2O2 concentration, and initial TC dosage. The obtained results indicated that the TC removal reached up to 82.3% with an initial TC dose of 8 μg/L. In addition, the TC degradation process is more effective in an acidic medium than in an alkaline medium. Furthermore, the TC removal reached up to 85.1% with a ZVI/Cu dose of 1.2 g/L. On the other hand, the optimum mixing intensity value was 200 rpm, and the optimum H2O2 dose was 2 g/L according to the conditions of the present study.

Novel NbCo-MOF as an advanced peroxymonosulfate catalyst for organic pollutants removal: Growth, performance and mechanism study

Multivariate metal-organic frameworks (MTV-MOFs) are expected as catalyst to apply to the advanced oxidation processes (AOPs) based on sulfate radical (SO4·−) to treat wastewater containing organic pollutants. Mixing metals de novo method was combined with stringent solvothermal conditions to synthesize macaroon-like NbCo-MOF catalyst. NbCo-MOF catalyst prepared with different atom ratios and growth time presented various morphology, structure, performance, and distinctive MTV-MOFs growth law which were confirmed by SEM, TEM, EDS, XRD, FTIR, raman spectra and UV–vis spectra. Besides, optimum peroxymonosulfate (PMS) catalytic activation conditions were studied. Furthermore, the effects of anions (Cl−, NO3−, HCO3−, and C2O42−) on NbCo-MOF catalytic activation were explored which were proved very limited. Particularly, the Co2+/Co3+ cycle combining with the Nb4+/Nb5+ cycle for PMS activation were verified by XPS. EPR and quenching experiment results indicated exists non-radical pathway (1O2), but radical pathways are dominant (SO4·− O2·−, and ·OH). Moreover, the TC removal rate exhibited no significant reduce after three times run. Furthermore, NbCo-MOF exhibited excellent decomposing ability towards methylene blue, tylosin tartrate, rhodamine B, and tetracycline with the removal rate reaching to 100%, 98.4%, 99.7%, and 99.7% in 30 min respectively and also maintained good performance in actual water environment.

Bifunctional two-dimensional copper-aluminum modified filter paper composite for efficient tetracycline removal: Synergy of adsorption and reusability by degradation

Herein, bifunctional two-dimensional copper-aluminum modified filter paper composite (2D-Cu/Al–C) was successfully prepared by simple calcination and showed ultrahigh adsorption performance and degradation potential. The adsorption removal of TC on 2D-Cu/Al–C all exceeded 92.2% under solution conditions of 10–200 mg/L TC, 100 mg/L 2D-Cu/Al–C, pH 8 and 298 K. The pseudo-second-order kinetic and Langmuir models better fitted the kinetic and isotherm data via spontaneous and exothermic process, and the maximum capacity of the 2D-Cu/Al–C was 2391.78 mg/g. Additionally, 2D-Cu/Al–C showed desired specific adsorption for TC (TC: 98.7%, norfloxacin: 5.8%, sulfamethoxazole: 2.1%, and ciprofloxacin: 1.8%) and it could effectively adsorbed TC even in the binary system (various coexisting ions or natural organic matter). After TC adsorbed on adsorbent was mineralized into CO2 and H2O by adding peroxydisulfate to generate high electrode potential radical in another limited systems, the 2D-Cu/Al–C still had ∼89.12% on TC removal (initial concentration of 50 mg/L) after five experimental cycles. Zeta potential, FT-IR and XPS results indicated that the multi-adsorption mechanism, including electrostatic interactions, complexation, and H-bonds, played a vital role in the fast and efficient adsorption process. Thus, the way of combining adsorption and regeneration via degradation are green, non-polluting strategy which are expected to be applied for water purification in future environmental remediation.

Hypolimnion behavior of technetium in freshwater at various stages of eutrophication

The article presents a study of various mechanisms of hypolimnion technetium behavior which occur at different stages of waterbodies eutrophication. Eutrophication stage was found to be positively correlated with the rate of 99Tc removal from water phase. The study identified a complex biogeochemical mechanism of technetium behavior. Planktonic phototrophic community plays a pivotal role in such a mechanism by ensuring fast oxygen consumption in hypolimnion. This creates favorable conditions for the active development of anaerobic bottom bacteria of sulfur and iron cycles given nutrients inflow. Sulfates and nitrates were discovered to have inhibitory effect on 99Tc biosorption by bottom sediments due to oxidizing conditions. Apart from the shift of redox potential of the medium to reducing values, the 99Tc removal and partial immobilization are also promoted by the presence of inorganic mineral phases of reduced sulfur and iron. These phases form a reducing barrier in the silt, thus preventing the oxidation and migration of technetium. We suggest the ways of stimulating in situ waterbody remediation by means of various additives, which will allow irreversible immobilization of technetium in silt once several growth periods have passed.

Simultaneous immobilization of aqueous co-contaminants using a bismuth layered material

The remediation of co-located contaminants in the vadose zone can be challenging due to accessibility and responses of different contaminants to remedial actions. At the Hanford Site (WA, USA), multiple radionuclides and other hazardous contaminants are present in the vadose zone and groundwater, including iodine-129 (I), technetium-99 (Tc), uranium-238 (U), chromium (Cr), and nitrate (NO3−). We evaluated a layered Bi oxyhydroxide material for its potential to remove individual and co-located contaminants with a series of batch experiments that investigated a range of plume conditions, followed by solid phase characterization of the reacted bismuth material. The results demonstrated successful removal of four contaminants (>98% removal of I, Tc, U, and Cr from the aqueous phase after 30 days) when tested individually. When contaminants were combined, a slight decrease in Tc removal occurred (−6%p). The addition of sediment decreased the removal for Tc and I, but U and Cr removal was unaffected. The results of these batch tests demonstrated that the bismuth based oxy-hydroxide material is a promising material for sequestering multiple contaminants in situ.

Magnetic porous biochar with high specific surface area derived from microwave-assisted hydrothermal and pyrolysis treatments of water hyacinth for Cr(Ⅵ) and tetracycline adsorption from water

Magnetic porous water hyacinth-derived biochar (MPBCMW3) was synthesized via two-step Microwave (MW)-assisted processes. Characterization results not only testified high specific surface area (2097.50 m2/g) of the MPBCMW3 assisted by MW-assisted pyrolysis, but also revealed its favorable magnetism derived from MW-assisted hydrothermal process. The MPBCMW3 possessed pH-dependent monolayer adsorption capacities of 202.61 and 202.62 mg/g for Cr(VI) and TC with quick attainments of uptake equilibrium within 150 and 200 min. Moreover, the Cr(VI) and TC uptake were substantially steady under the interference from multifarious co-existing ions with slight decline after three adsorption–desorption cycles. Furthermore, the MPBCMW3 was demonstrated to achieve excellent Cr(VI) binding primarily through complexation, electrostatic interaction, reduction and ion exchange, while presenting outstanding TC removal via pore filling, π-π stacking, hydrogen bonding force, electrostatic interaction and complexation. All these findings suggested the MPBCMW3 synthesized by MW-assisted processes as an excellent adsorbent for purification of Cr(VI) and TC-contaminated water.

Development of new adsorbents via microwave treatment magnetic PET synthesis from waste PET and investigation of TC removal

In this study; new, economic and environment friendly adsorbents were synthesized using waste polyethylene terephthalate based adsorbent, derived from waste PET bottles, WPET, nano-scale zero valent iron modified adsorbent nZVI-WPET and microwave energy pre-treatment applied adsorbent MW/WPET-nZVI for TC removal. The synthesized composite was characterized using various techniques such as EDX, FT-IR XRD and SEM. Maximum adsorption values were obtained for all adsorbents at pH 5.0, with adsorbent amount of 10.0 g/l, at 20 C’ and with initial TC concentration of 50 mg/l as a result of which the highest adsorption yield was obtained for WPET, WPET- nZVI and 2 min MW/WPET- nZVI as; 92.42%, 93.10%, 93.38% respectively. Maximum adsorption capacities, values were determined as 67.11 mg/g, 80 mg/g and 105.26 for WPET, WPET-nZVI and 2 min MW/WPET-nZVI. Adsorption isotherms parameters were modeled for new adsorbents and the best fit achieved with Freundlich isotherms for TC removal process.

Micrometer-sized magnetite synthesis using Fe(OH)2(s) as a precursor for technetium sequestration from liquid nuclear waste streams

• Transformation of Fe(OH) 2 (s) to micrometer-sized magnetite in waste stream at 75 °C. • Solution pH/temperature/oxidation kinetics play key roles in final mineral products. • An increase in pH or Fe(II) amendment improved tc removal from waste streams. • Tc sequestration as TcO 2 •2H 2 O or through Tc(IV)-magnetite incorporation. • More tc incorporation into magnetite at elevated temperatures and pH conditions. Systematic batch experiments under variable adjusted physicochemical conditions were conducted to explore optimization of micrometer-sized magnetite synthesis for Tc sequestration from radionuclide waste streams using Fe(OH) 2 (s) as the precursor. Extensive solid characterizations using X-ray diffraction, microscopy and spectroscopic methods were performed to identify mineral phases, assess changes in particle morphology and size distribution, as well as Tc speciation and incorporation, in the produced mineral phases. The results show that the solution pH, temperature, and oxidation kinetics play key roles in the final mineral products. Micrometer-sized magnetite crystals (0.62–0.96 µm, on average) with well-defined dodecahedral or octahedral structures were synthesized under near neutral (~pH 8) or alkaline (~pH 13) conditions at 75 °C, respectively; whereas goethite dominated the end products at room temperature. An increase in pH at 75 °C improved Tc removal from 27% (near neutral pH) to 42% (alkaline pH), but the removal process remained inhibited by redox-competitive Cr(VI) present in the waste streams. By adding additional Fe(II) to the system, Tc sequestration was dramatically improved up to 87% without observable changes in the solid product. The sequestrated Tc existed as TcO 2 •2H 2 O and/or Tc(IV) incorporated into magnetite, where extended X-ray absorption fine structure (EXAFS) spectroscopy showed that more Tc was incorporated into magnetite at elevated temperatures and pH conditions, with complete Tc(IV) incorporation into magnetite occurring under 75 °C-pH 13 conditions. Our results indicate that optimal micrometer-sized magnetite can be produced for Tc sequestration by reacting Fe(OH) 2 (s) with a waste stream simulant under elevated pH (~13) and temperature (75 °C) conditions. The incorporation of reduced Tc(IV) into stable micrometer-sized magnetite provides a viable supplemental immobilizing technology that may be used to improve nuclear waste treatment and disposal needs.

Design of core-shelled g-C3N4@ZIF-8 photocatalyst with enhanced tetracycline adsorption for boosting photocatalytic degradation

Abstract Confining active species and intermediates in a limited spatial is critical to driving pollutant transformation involving successive reactions for boosting degradation. Herein, core–shell g-C3N4@ZIF-8 were prepared by exfoliating-wrapping of g-C3N4 via ZIF-8 in-situ growth. XRD, SEM, TEM, and EDX mapping demonstrate the inclusion of curled g-C3N4 sheets in ZIF-8. UV–vis, PL, FTIR, and XPS confirm the coordination of TC with Zn of ZIF-8. Steady-transient PL, EIS and transient photocurrent response indicate that the combination of two materials favors the carriers’ separation and transfer. Further band analysis suggests that interfacial band bending of g-C3N4 promotes the separation of electron-hole and electron diffusion toward ZIF-8. As result, the optimized g-C3N4@ZIF-8 exhibits a superior TC degradation rate constant (k = 0.068 min−1), 4.8 times higher than that of g-C3N4 (k = 0.014 min−1), and enhanced TC removal rate of 87.6% higher than g-C3N4 (58.6%). Also, the optimized material shows superior degradation rate and removal efficacy in RhB (99.3%) and Cr (VI) (96.6%) in surface water. The investigations on active species and degradation routes (EPR, LC-MS) reveal that synergetic effects of ZIF-8 confined g-C3N4 facilitate the formation of oxygen radicals ( O2−) and their transformation toward singlet oxygen (1O2) for boosting TC degradation.

Hierarchical CoTiO3@NiO core–shell sub-microbelts as direct Z-scheme photocatalyst for efficient visible-light-driven tetracycline degradation

The hierarchical binary 1D@2D CoTiO3@NiO Z-scheme heterojunctions with well-defined core–shell feature display the enhanced photocatalytic activity for antibiotic tetracycline decomposition under visible light illumination. The obtained CoTiO3@NiO heterostructured sub-microbelts show a superior photocatalytic efficiency to the pristine CoTiO3 sub-microbelts, and NiO nanoclusters. The TC removal efficiency of CoTiO3@NiO sub-microbelts is 1.75 and 2.15 times higher than that of pristine CoTiO3, and NiO, respectively. The electrospinning CoTiO3 sub-microbelts are decorated uniformly with in situ nanosheets of NiO longitudinally aligned through a facile two-step precipitation-calcination processure. The Z-scheme heterojunctions consisting of CoTiO3 and NiO efficiently accelerate photo-generated electron-hole separation efficiency, and afford a high specific surface area, which ultimately improve the efficiency of TC degradation. The profitable carrier transmission mechanism and special core–shell structure in the CoTiO3@NiO system are in charge of the elevated catalytic activity because of the formed Z-scheme system. These features demonstrate that the hierarchical CoTiO3@NiO core–shell heterojunctions have the great application potential for tetracycline removal from wastewater.

Mechanism of nitrogen-fluoride co-doped TiO2/bentonite composites removing tetracycline: A study in the co-doping ratio

N-doped and N-F co-doped TiO2/bentonite composites were synthesized via the gel-sol method. The morphology, structure and surface charge of the composite before and after adsorption were used to determine the effect N/F doping ratio on TC removal. The results showed that, compared with undoped samples, the TC adsorption on N doped composites was reduced by 24.44% on average. N-F co-doping significantly increased the TC adsorption when the Ti-N-F molar ratio was 1:1: 0.01, reaching a maximum TC adsorption of 64.00 mmol·kg<sup>-1</sup>. The coverage of the N doped TiO2 increases as the N doping ratio increases; the specific surface area increased by 2.03 % on average, but the number of surface negative charges decreased by 36.24 % on average. FT-IR results confirmed that N doping reduced the number of -OH groups on the N-doped composites. Additionally, fluorination of N-F co-doped TiO2 and bentonite surfaces inhibits hydrogen bonding and π-π interactions between the TC and the composites. As the N doping ratio increased, the coverage of N-F co-doped TiO2 on the composite surface increased, resulting in the TC adsorption decrease with the increases N doping ratio.

Construction of novel Zn2TiO4/g-C3N4 Heterojunction with efficient photodegradation performance of tetracycline under visible light irradiation.

This work presented facile fabrication of carbon nitride (CN)/zinc titanate (ZT) heterojunction by one-step ball milling process for visible light-induced photocatalytic degradation. The phase structures, morphologies, functional groups, and optical properties of the prepared materials were systematically characterized by XRD, FTIR, UV-Vis DRS, and SEM techniques. The ball milling for 10min significantly improved visible light absorption properties; the as-synthesized ZT/CN catalyst (2.8eV) showed lower band gap energy than bare ZT (3.2eV). This result revealed a successful incorporation. The photocatalytic activities of the heterostructure catalysts (ZT/CN) evaluated by degrading tetracycline under visible light irradiation and highest TC removal rate were obtained as 0.0193min-1 for ZT/CN/5, which was 6.2 times higher than that of bare CN. The most efficient photocatalyst (ZT/CN/5) could be performed three times without any loss of phase. In addition, the heterostructure catalyst was found as promising candidate for efficient photocatalytic degradation of other antibiotics and dye components.