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Thiourea-dioxide–reduced magnetic graphene oxide (TDMGO) was successfully prepared as an efficient adsorbent for the removal of tetracycline (TC) from aqueous solutions via strong adsorptive interactions. The composite was characterized by SEM, TEM, EDS, TGA, FT-IR, XPS, XRD and VSM. The effects of variables such as the pH, TC concentration, and temperature were successfully analyzed. The kinetics and isothermal parameters were described well by pseudo-second-order and Langmuir isotherm models, respectively, and the maximum adsorption capacity ( q m ) of TDMGO for TC calculated from the Langmuir isotherm was 1233 mg/g at 313 K. The removal of TC onto TDMGO, as indicated by the thermodynamic parameters, was spontaneous and endothermic. The removal performance was slightly affected by the solution pH. The presence of NaCl in the solution facilitated TC adsorption, and the optimum adsorption capacity was obtained when the NaCl concentration was >0.001 M. The adsorption capacity decreased slightly with increasing humic acid concentration. In addition, the adsorbent could be regenerated and reused. Based on these results, TDMGO is a promising adsorbent for the efficient removal of TC antibiotics from aquatic environments for pollution treatment. [ABSTRACT FROM AUTHOR]

A novel PbMoO4@MBC (MBL-2) magnetic heterojunction photocatalyst was prepared by the successful loading of Fe3O4 with PbMoO4 onto the highly conductive BC surface through the integration of co-precipitation and pyrolysis. Using advanced characterization methods could reveal the composition, morphology, and optoelectronic properties of the material. The results showed that using BC as the electron transfer interface provided a pathway for charge transfer between Fe3O4 and PbMoO4, and importantly, the PbMoO4@MBC (MBL-2) nanocomposite had a large specific surface area, excellent magnetic response, high light absorption capacity for efficient carrier separation, and thus the photocatalytic activity was high. The degradation rate of MBL-2 for TC under visible light was as high as 89%. More importantly, PbMoO4@MBC (MBL-2) possessed good stability and reusability. The Z-scheme electron transfer pathway for improved photocatalytic performance was proposed by radical capture experiments and electron spin resonance (ESR) measurement analysis. [ABSTRACT FROM AUTHOR]

In the present work, a series of magnetically separable Fe3O4/g-C3N4/MoO3 nanocomposite catalysts were prepared. The as-prepared catalysts were characterized by XRD, EDX, TEM, FT-IR, UV-Vis DRS, TGA, PL, BET and VSM. The photocatalytic activity of photocatalytic materials was evaluated by catalytic degradation of tetracycline solution under visible light irradiation. Furthermore, the influences of weight percent of MoO3 and scavengers of the reactive species on the degradation activity were investigated. The results showed that the Fe3O4/g-C3N4/MoO3 (30%) nanocomposites exhibited highest removal ability for TC, 94% TC was removed during the treatment. Photocatalytic activity of Fe3O4/g-C3N4/MoO3 (30%) was about 6.9, 5, and 19.9-fold higher than those of the MoO3, g-C3N4, and Fe3O4/g-C3N4 samples, respectively. The excellent photocatalytic performance was mainly attributed to the Z-scheme structure formed between MoO3 and g-C3N4, which enhanced the efficient separation of the electron-hole and sufficient utilization charge carriers for generating active radials. The highly improved activity was also partially beneficial from the increase in adsorption of the photocatalysts in visible range due to the combinaion of Fe3O4. Superoxide ions (·O2−) was the primary reactive species for the photocatalytic degradation of TC, as degradation rate were decreased to 6% in solution containing benzoquinone (BQ). Data indicate that the novel Fe3O4/g-C3N4/MoO3 was favorable for the degradation of high concentrations of tetracycline in water. [ABSTRACT FROM AUTHOR]

Modifying energy band structure and increasing absorption are two efficient strategies to improve the photocatalytic performance of semiconductor photocatalysts. In this study, a novel biochar (BC) based photocatalyst, nitrogen-doped (N-doped) BC based PbMoO 4 (NPBC) was developed by combining both strategies. After loading PbMoO 4 on poplar sawdust via in situ method, the composites were pyrolyzed in the presence of a certain amount of urea. Nitrogen doping successfully increased the specific surface area and narrowed the bandgap of the composite of PbMoO 4 @BC (PBC) to improve its adsorption-photocatalytic performance. NPBC-2, in which the ratio of PbMoO 4 : poplar sawdust was 3:1.6, exhibited excellent adsorption-photocatalytic removal for 40 mg L−1 tetracycline (TC) under visible light and the total removal rate was 88.25%, which was 1.60 and 3.46 folds of that for PBC and PbMoO 4, respectively. The adsorption kinetic of TC removal by NPBC-2 fitted well with pseudo fist order models, and the adsorption was dominated by the physical process. Vacancies (h+) and superoxide radicals (•O 2 −) were the main active species for TC photodegradation. In addition, after 5 cycles, the composite still exhibited high ability for TC removal. Therefore, N-doped BC based photocatalysts provided a feasible and effective way for the remediation of organism-contaminated water. • A novel PbMoO 4 @NBC catalyst was synthetic by combing precipitation and calcination. • The N doping shorten the band gap of the PBC. • The N-doped on PBC enhanced separation efficiency of electron-hole pairs. • The N-doped on PBC improved the adsorption capacity and removal efficiency of TC. [ABSTRACT FROM AUTHOR]

Developing broad-spectrum light reactions, effective charge separation, and easily recoverable photocatalysts were considered cost-effective pollution remediation methods. The ZnFe 2 O 4 /BC/ZnO composite was prepared to achieve these objectives, where biochar (BC) was used as a conductive channel and ZnFe 2 O 4 as a magnetic substance. Among them, the 0.6-ZBO composite performed the best, with photocatalytic removal of tetracycline (TC) reaching 85.6%. The photocatalytic degradation rated constant of 0.6-ZBO composite was 23.36 × 10−3 min−1, which was 7.6, 4.1, and 2.5 times higher than that of ZnFe 2 O 4 /BC, ZnO, and ZnFe 2 O 4 /ZnO samples, respectively. According to several characterization data, it was demonstrated that successful Z-scheme heterojunctions were constructed between ZnFe 2 O 4 and ZnO. The 0.6-ZBO complex increased the range of light absorption and strengthened the separation of electron-hole pairs, thus improving the redox ability of the complex. In the different water matrices, the stability of 0.6-ZBO was excellent and its ability to remove TC decreased slightly to about 11% after 5 cycles. This work provided a valuable approach to design a novel and efficient system for degrading organic pollutants in wastewater using magnetic biochar. [Display omitted] • A novel ZnFe 2 O 4 /BC/ZnO (ZBO) Z-scheme heterojunction was successfully constructed. • The ZBO heterojunction promotes the separation of electron-hole pairs. • BC as a conductive channel of ZnO and ZnFe 2 O 4. • The ZBO composite was relatively effective to remove TC from the wastewater. [ABSTRACT FROM AUTHOR]

Developing efficient and economical photocatalysts was considered as an efficient and economical strategy for pollution remediation. Herein, magnetically separable ZnFe 2 O 4 /CuWO 4 composites (ZW) had been developed via combining ZnFe 2 O 4 with CuWO 4. The composite with a mass ratio of 40% CuWO 4 (ZW-40) performed best, and the tetracycline hydrochloride (TC) removal by adsorption-photocatalysis of ZW-40 reached 86.5%. The photocatalytic degradation rated constant of it was 9.44 × 10−3 min−1, which was approximately 5.04 and 3.28 times compared to the ZnFe 2 O 4 and CuWO 4 samples, respectively. Pseudo-second-order kinetic models could describe well the TC adsorption process, in which chemisorption was the major driving factor, with the maximum adsorption at 23.56 mg g−1. The improved photo-catalytic capability owed to the formation of Z-scheme heterojunctions with ZnFe 2 O 4 and CuWO 4 , which improved the intensity of visible light absorption and enhanced the separation electron-hole pairs as well as the redox capability of the composite. ZW-40 was high stability as its removal ability of TC in different water conditions slightly dropped about 15% after 5 cycles. ZW-40 could effectively remove TC in different water matrix, its removal ability for 40 mg/L was as follows: super-pure water> municipal wastewater> swine farm wastewater. Hence, the complexation of ZnFe 2 O 4 with CuWO 4 provides a valuable strategy to improve the photocatalytic potential for ZnFe 2 O 4 -based catalysts as well as providing a promising pathway for water clarification. • A novel ZnFe 2 O 4 /CuWO 4 (ZW) Z-scheme heterojunction was successfully constructed. • Heterojunction between ZnFe 2 O 4 and CuWO 4 promotes the electron-hole pair separation. • Synergistic adsorption-photocatalysis could more effectively remove tetracycline. • The ZW composite was relatively effective to remove TC from the wastewater. [ABSTRACT FROM AUTHOR]

For highly efficient photocatalytic remediation of organic pollutants, broad-spectrum light response and effective charge separation are two key goals. To achieve these goals, a novel biochar (BC) modified PbMoO 4 composite catalyst was successfully synthesized in situ by combining coprecipitation with pyrolysis treatment of poplar sawdust and the technical feasibility of degradation of tetracycline (TC) with compound photocatalyst prepared from recovered agricultural and forestry residues was preliminarily demonstrated. The characterization demonstrated that the presence of BC narrowed the bandgap, enhanced visible light absorption as well as facilitated charge separation. Three composites (with the mass ratio of PbMoO 4 to BC = 1:4; 1:1; and 4:1, respectively) displayed higher activity than pure PbMoO 4. The results showed that the composite with the PbMoO 4 to BC ratio of 1:4 exhibited the best photocatalytic activity, for 150 mg L−1 TC the removal rate was 61.0%, and the rate constant was 8.1 × 10−3 min−1, while the photocatalytic activity of PbMoO 4 was 26.0% and 3.9 × 10−3 min−1. The reactions in the presence of radical quenchers indicated that holes (h+) and superoxide radicals (O 2 −) were the dominant active species for photodegradation. In different water matrices, for 150 mg L−1 TC solution the photocatalytic activity of optimal photocatalyst decreased as follows: ultrapure water > artificial sewage > farm sewage > municipal sewage. Moreover, the catalyst exhibited good stability over five cycles. Therefore, BC doped PbMoO 4 provides a useful strategy for improving the photocatalytic ability of PbMoO 4 -based photocatalysts and offers a promising method for water purification. [Display omitted] • Using poplar sawdust as biochar source realized the rational application of waste. • In situ synthesis enhanced the adsorption and photocatalytic activity of PbMoO 4. • Superior electrical conductivity of BC helps transport of photogenerated carrier. • BC strengthened the visible light response of PbMoO 4 @BC-1. • PbMoO 4 @BC-1 showed promising visible-light photodegradation for TC degradation. [ABSTRACT FROM AUTHOR]