One-pot synthesis of N-doped carbon intercalated molybdenum disulfide nanohybrid for enhanced adsorption of tetracycline from aqueous solutions

Removal of Mo(VI), Pb(II), and Cu(II) from wastewater using electrospun cellulose acetate/chitosan biopolymer fibers

Environmentally friendly polymers such as cellulose acetate (CA) and chitosan (CS) were used to obtain electrospun fibers for Cu2+, Pb2+, and Mo6+ capture. The solvents dichloromethane (DCM) and dimethylformamide (DMF) allowed the development of a surface area of 148 m2 g-1 for CA fibers and 113 m2 g-1 for cellulose acetate/chitosan (CA/CS) fibers. The fibers were characterized by IR-DRIFT, SEM, TEM, CO2 sorption isotherms at 273 K, Hg porosimetry, TGA, stress-strain tests, and XPS. The CA/CS fibers had a higher adsorption capacity than CA fibers without affecting their physicochemical properties. The capture capacity reached 102 mg g-1 for Cu2+, 49.3 mg g-1 for Pb2+, and 13.1 mg g-1 for Mo6+. Furthermore, optimal pH, adsorption times qt, and C0 were studied for the evaluation of kinetic models and adsorption isotherms. Finally, a proposal for adsorbate-adsorbent interactions is presented as a possible capture mechanism where, in the case of Mo6+, a computational study is presented. The results demonstrate the potential to evaluate the fibers in tailings wastewater from copper mining.

Magnetic MnFe2O4/ZIF-67 nanocomposites with high activation of peroxymonosulfate for the degradation of tetracycline hydrochloride in wastewater

Advanced oxidation processes (AOPs) based on PMS have been used to degrade various refractory pollutants such as drugs, endocrine disruptors, dyes and perfluorinated compounds due to their wide application range, mild reaction conditions, fast reaction rate and simple operation. In this study, tetracycline hydrochloride (TCH) was degraded based on this method. Magnetic MnFe2O4/ZIF-67 nanocomposites were successfully prepared by a hydrothermal method, which combined the magnetic separation characteristics of MnFe2O4 with the high catalytic activity of ZIF-67 and were used to activate peroxymonosulfate (PMS) to efficiently degrade TCH. Satisfactory removal results were obtained with this simple and readily available material, with 82.6% of TCH removed in 15 min. The effect of different conditions on the degradation effect was investigated, and the optimal catalyst concentration and PMS concentration were determined to be 0.1 g L-1 and 0.2 g L-1, respectively, and all had good degradation effects at pH 5 to 10. XPS, impedance test and radical quenching experiments were used to investigate the degradation mechanism. The results showed that sulfate radical (SO4-˙) was the main active species in the degradation process. In addition, the catalyst has good cyclic stability, which provides a new idea for the removal of TCH in wastewater. It is worth mentioning that the catalyst also has good degradation property for other pollutants.

Single and multi-antibiotics removal via peroxymonosulfate activation using molybdenum disulfide (MoS2): Central composite design and degradation pathway

The efficacy of molybdenum disulfide (MoS2) for the degradation of metronidazole (MET), tetracycline (TET), and ciprofloxacin (CIP) in single and multicomponent systems through peroxymonosulfate (PMS) activation was investigated. Several characterization techniques, such as SEM, XRD, XPS, and EPR were performed to understand the removal mechanism of the three antibiotics in PMS/MoS2 system. In single component system with an initial antibiotic concentration of 10 mg L-1, >95% removal of MET, TET, and CIP were observed within 60 min (PMS = 100 mg L-1; MoS2 = 0.5 g L-1). It was observed that sulfate radical (SO4.-) and reactive ≡Mo- OOSO3- complex played a major role in the removal of antibiotics. Adsorption on MoS2 and direct oxidation by PMS contributed to the removal of TET and CIP in MoS2/PMS system. A Central composite design (CCD) with response surface methodology (RSM) was used to model the removal of MET, TET, and CIP in a multi-antibiotic system. The presence of multiple antibiotics affected the performance of MoS2/PMS system as antibiotics competed for the adsorption sites on MoS2 and the generated reactive species. CIP predominantly deterred the removal of both MET and TET. On the other hand, MET removal was decreased up to 25-40% in the presence of both TET and CIP. Similarly, TET removal decreased up to 15-20% in the presence of MET and CIP. CIP removal decreased up to 15-25% in the presence of MET and TET. In the presence of multiple antibiotics, the deterring effect of one pollutant over another can be overcome by increasing the MoS2 concentration above 1200 mg L-1 and PMS above 200 mg L-1 to obtain 100% removal of all three pollutants. Overall, MoS2 could be an ideal catalyst for the removal of antibiotics through PMS activation.

Intensive adsorption of tetracycline by cobalt oxide quantum dots-loaded mineral carbon

Spent bleaching earth (SBE), a waste by-product produced from the bleaching step of edible oil by montmorillonite clays (bleaching earth), causes serious public health and environmental problems. Accordingly, in this study, SBE was pyrolyzed to yield mineral carbon materials (SBE@C) and cobalt oxide (Co3O4) was loaded to improve the active site of those materials. Due to the carrier function of SBE@C, ultra-fine Co3O4 quantum dots (QDs) (2-6 nm) were homogeneously and robustly immobilized onto SBE@C. The obtained adsorbent exhibited high regeneration performance and an outstanding adsorption capacity (253.36 mg/g). It can be attributed to the surface complexation of cobalt with TC being the dominant process contributing to adsorption behavior. Further, Co3O4 QDs-SBE@C still maintained adequate sorption capacity at a broad range of pH values and in the presence of co-occurring ions. These results suggested the significant application potential of SBE and demonstrated the efficiency of using Co3O4 QDs-SBE@C for wastewater remediation.

Removal of tetracycline in aqueous solution by iron-loaded biochar derived from polymeric ferric sulfate and bagasse

In this study, the tetracycline (TC) removal performance of iron-loaded biochar (BPFSB) derived from sugarcane bagasse and polymerized iron sulfate was investigated, and the mechanism of TC removal was also explored by study of isotherms, kinetics and thermodynamics and characterization of fresh and used BPFSB (XRD, FTIR, SEM and XPS). The results showed that under optimized conditions (initial pH 2; BPFSB dosage 0.8 g·L-1; TC initial concentration 100 mg·L-1; Contact time 24 h; temperature 298 K), the removal efficiency of TC was as high as 99.03%. The isothermal removal of TC followed well the Langmuir, Freundlich, and Temkin models, indicating that multilayer surface chemisorption dominated the TC removal. The maximum removal capacity of TC by BPFSB at different temperatures was 185.5 mg·g-1 (298 K), 192.7 mg·g-1 (308 K), and 230.9 mg·g-1 (318 K), respectively. The pseudo-second-kinetic model described the TC removal better, while its rate-controlling step was a combination of liquid film diffusion, intraparticle diffusion, and chemical reaction. Meanwhile, TC removal was also a spontaneous and endothermic process, during which the randomness and disorder between the solid-liquid interface was increased. According to the characterization of BPFSBs before and after TC removal, H-bonding and complexation were the major interactions for TC surface adsorption. Furthermore, BPFSB was efficiently regenerated by NaOH. In summary, BPFSB had the potential for practical application in TC removal.

Preparation of Molybdenum Disulfide with Different Nanostructures and Its Adsorption Performance for Copper (Ⅱ) Ion in Water

The environmental problems in the world are attracting increasing amounts of attention, and heavy metal pollution in the water has become one of the focuses of the ecological environment. Molybdenum disulfide (MoS₂) has excellent adsorption performance because of its extremely high specific surface area and unique active site structure, which has attracted an increasing amount of attention in the field of heavy metal disposal in various types of water. In this paper, two sorts of MoS₂ nanoparticles, spherical and lamellar, were synthesized by different chemical methods. Their morphology and structure were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and a Raman spectrometer. The adsorption properties of two sorts of MoS₂ nanoparticles for copper (Ⅱ) ions in water were investigated by changing the pH value, adsorption time, initial concentration of solution, adsorption temperature, etc. Finally, the adsorption mechanism was analyzed by kinetic, isothermal, and thermodynamic models. The results show that two microstructures of MoS₂ nanoparticles can be used as efficient adsorption materials for removing heavy metal ions from water, although there are differences in adsorption capacity between them, which expands the theoretical basis of heavy metal adsorption in a water environment.

Algae extract delamination of molybdenum disulfide and surface modification with glycidyl methacrylate and polyaniline for the elimination of metal ions from wastewater

A special type of two-dimensional (2D) material based conducting polymer was constructed by green synthesis and in-situ polymerization techniques. The 2D Molybdenum Disulfide (MoS₂) were first synthesized with the combination of, ammonium tetrathiomolybdate dissolved in 20 mL algae extract under stirring. After stirring for about 2 h, and then finally sulfurization was initiated using sulfur powder in 20 mL of sulfuric solution and stirred for 8 h. The resulting black precipitates of MoS₂ were collected by centrifugation at 5000 rpm. Moreover, the prepared MoS₂ was functionalized with glycidyl methacrylate (GMA) and form the MoS₂@PGMA. Further, the MoS₂@PGMA is combined with polyaniline (PANI) to form conducting polymer grafted thin film nanosheets named MoS₂@PGMA/PANI with a thickness in micrometer size through grafting method. The prepared materials were characterized by SEM, FTIR, XRD, XPS and EDX techniques. To check the performance of materials the adsorption study was performed. Moreover, the adsorption study toward Cu²⁺ and Cd²⁺ showed a tremendous results and the maximum adsorption was 307.7 mg/g and 214.7 mg/g respectively. In addition, the pseudo-first and second order models as well as the adsorption isotherm were investigated using the Langmuir and Freundlich model. The results were best fitted with the pseudo-second order and Langmuir models. The regeneration study was also conducted and MoS₂@PGMA/PANI nanosheets can be easily recycled and restored after five successful recycling. The established methodology for preparing the 2D materials and conducting polymer based MoS₂@PGMA/PANI nanosheets is expected to be applicable for other multiple applications.

Facile access to high-efficiency degradation of tetracycline hydrochloride with structural optimization of TiN

As a broad-spectrum antibiotic, tetracycline has become a potential ecological hazard. Herein, titanium nitride (TiN), with an advantageous structure, was synthesized by simple heating rate regulation and constructed for tetracycline hydrochloride (TC-HCl) degradation under light irradiation. All the samples were characterized by X-ray diffraction (XRD), N2-adsorption/desorption isotherm, ultraviolet-visible diffuse reflectometry (DRS), scanning electron microscopy (SEM), and electrochemical impedance spectroscopy (EIS). The results showed that the as-prepared TiN-x catalysts exhibited obviously enhanced photocatalytic property toward TC-HCl degradation compared with the commercial pure phase TiN (p-TiN). According to the results of photocatalytic degradation, TiN synthesized at 6 °C/min heating rate had the best removal rate of TC-HCl (90%) after dark reaction for 10 min and photo-degradation for 90 min. In addition, the trapping experiments have demonstrated that the photogenerated holes (h+) and superoxide radical ([Formula: see text]) are the main oxidation products of the present system. Strikingly, the reuse experiments showed high stability of TiN.

The removal performance and mechanisms of tetracycline over Mn-rich limonite

Naturally occurring Mn-rich limonite mainly composed of goethite and manganese oxides was used to remove tetracycline (TC) from the aqueous solution. The effects of dosage, initial solution pH, temperature, and coexisting anions on TC removal were investigated. Results showed that 95% of TC (30.0 mg·L^-1) was removed in a wide pH range of 3.0-9.0 by limonite with high specific surface area (145.0 m²·g^-1) and mesoporous structure. The presence of Cl^-, NO₃^-, and SO₄^2- in the studied concentration range did not influence TC removal efficiency significantly, while PO₄^3- inhibited the adsorption of TC over limonite due to the competition with TC for active sites. Integrated with the FT-IR analysis, electrostatic interaction and complexation were proved to be the adsorption mechanisms of TC by limonite. The quenching experiments and ESR analysis revealed that singlet oxygen (¹O₂) also was involved in TC degradation. In addition, limonite displayed an efficient recycling performance and stability after four cycles. This study revealed that the Mn-rich limonite was a promising adsorbent for TC removal from aqueous solutions and promoted the application of natural mineral material in the environmental field.

Obtaining high-value nitrogen-containing carbon nanosheets with ultrahigh surface area from waste sludge for energy storage and wastewater treatment

Recovering high value-added resources from waste activated sludge (WAS) is a potential way for the sustainable wastewater treatment. In this study, hydrothermal treatment at 180 °C was used to simultaneously improve sludge dewaterability and recover sludge organic matters (SOMs). The recovered SOMs were subsequently employed as precursors to prepare nitrogen-doped porous carbon nanosheets via a facile stepwise synthesis method. The as-prepared optimal carbon (AP-SOM₈₀₀) was characterized with an ultrahigh specific surface area (3473 m²/g), appropriate porosity (1.77 cm³/g), and abundant heteroatoms (1.47% N and 7.44% O). AP-SOM₈₀₀ exhibited a high specific capacitance (409 F/g at 0.25 A/g), low resistance (0.52 Ω), and superior cyclic stability (only 9.09% loss after 10,000 cycles) in 6 M KOH aqueous electrolyte. Furthermore, AP-SOM₈₀₀ demonstrated an extraordinary adsorption capacity (1528 mg/g for methyl orange (MO) and 1265 mg/g for tetracycline (TC)) that can be maintained (˃ 1200 mg/g) over a wide range of pH conditions. Specifically, 80.97% of MO and 66.67% of TC were rapidly absorbed through AP-SOM₈₀₀ within 10 min, and 90.27% of MO and 81.24% of TC were eventually removed from wastewater after 60 min. The adsorption processes fit closely with the pseudo-second-order kinetic (R² > 0.999) and Langmuir models (R² > 0.914), revealing that the adsorption processes were dominated by a monolayer chemical adsorption reaction. This study suggests that high value-added materials can be obtained from the WAS through improving and extending the traditional sludge treatment processes, which will enrich the technical options available for future sustainable sludge treatment and disposal.

Biosynthesis of SiO2 nanoparticles using extract of Nerium oleander leaves for the removal of tetracycline antibiotic

Tetracycline (TC) is one of the antibiotics that is found in wastewaters. TC is toxic, carcinogenic, and teratogenic. In this study, the tetracycline was removed from water by adsorption using dioxide silicon nanoparticles (SiO₂ NPs) biosynthesized from the extract of Nerium oleander leaves. These nanoparticles were characterized using SEM-EDX, BET-BJH, FTIR-ATR, TEM, and XRD. The influences of various factors such as pH solution, SiO₂ NPs dose, adsorption process time, initial TC concentration, and ionic strength on adsorption behaviour of TC onto SiO₂ NPs were investigated. TC adsorption on SiO₂ NPs could be well described in the pseudo-second-order kinetic model and followed the Langmuir isotherm model with a maximum adsorption capacity was 552.48 mg/g. At optimal conditions, the experimental adsorption results indicated that the SiO₂ NPs adsorbed 98.62% of TC. The removal of TC using SiO₂ NPs was 99.56% at conditions (SiO₂ NPs dose = 0.25 g/L, C₀ = 25 mg/L, and t = 40 min) based on Box-Behnken design (BBD) combined with response surface methodology (RSM) modelling. Electrostatic interaction governs the adsorption mechanism is attributed. The reusability of SiO₂ NPs was tested, and the performance adsorption was 85.36% after the five cycles. The synthesized SiO₂ NPs as promising adsorbent has a potential application for antibiotics removal from wastewaters.

Synthesis of Cu3P/SnO2 composites for degradation of tetracycline hydrochloride in wastewater

Antibiotic drugs have become dominating organic pollutants in water resources, and efficient removal of antibiotic drugs is the priority task to protect the water environment. Cu₃P/SnO₂ photocatalysts of various Cu₃P loadings (10-40 wt% Cu₃P) were synthesized using a combination of hydrothermal synthesis and a partial annealing method. Their photocatalytic activity was tested for tetracycline hydrochloride (TC-HCl) degradation under visible light irradiation. Cu₃P/SnO₂ samples were characterized by X-ray diffraction (XRD), N₂-adsorption, ultraviolet-visible diffuse reflectance spectra (UV-vis DRS), scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). The results showed that the p-n type heterostructure between Cu₃P and SnO₂ was successfully constructed, and addition of Cu₃P to SnO₂ could improve its photocatalytic activity at an optimized loading of 30 wt% Cu₃P. In photocatalytic degradation studies, removal rates of around 80% were found in 30 minutes of dark reaction and 140 min of photodegradation. The removal rate was superior to that of Cu₃P and SnO₂ alone under the same experimental conditions. According to trapping experiments and electron spin resonance (ESR) measurements, photogenerated holes (h⁺) and superoxide radicals ˙O₂ ^- were considered as the main oxidation species in the present system. Finally, the reuse experiments showed high stability of Cu₃P/SnO₂. This study reports Cu₃P as a cocatalyst combined with semiconductor SnO₂ to form a highly efficient heterogeneous photocatalyst for the degradation of tetracycline hydrochloride for the first time.