Novel 2D photocatalyst of copper-doped carbon quantum dot CD(Cu) loaded with ultrathin Ni-MOL for degradation of tetracycline.

Broadening the light absorption range and suppressing the carrier complexation are the two keys to enhance the photocatalytic activity. In this work, a novel two-dimensional (2D) photocatalyst was successfully prepared by modified hydrothermal method and applied in tetracycline (TC) degradation. The degradation rate of CD(Cu)-Ni-MOL for TC reached 93.5% within 60 min under the visible light condition. The improved photocatalytic performance of CD(Cu)-Ni-MOL was attributed to the constructed 2D layered structure and the special properties of CD(Cu). The doped Cu in carbon dots (CDs) exhibited excellent photocatalytic performance among the elements of Cu, Zn, Ni, Co and Fe. The order of photocatalytic performance improvement was Cu > Zn > Ni > Co > Fe. In addition, a possible degradation pathway for TC was proposed. This work confirms the great potential of CD(Cu)-Ni-MOL as a highly efficient photocatalyst in removing tetracycline pollutants in water.

Ni-MOL/In2Se3 heterostructure construction with mixed metal (Ti/Ni) for efficient photocatalytic tetracycline degradation.

To investigate the mechanism of bimetallic 2-dimension (2D) catalyst existing in the current photocatalytic degradation process, the tetracycline (TC) degradation performance and mechanism by bimetallic 2D photocatalyst was studied extensively. Nickel metal-organic layer (Ni-MOL) and In2Se3, a typical 2D semiconductor photocatalyst, shows great potential for photocatalytic degradation of TC. Herein, an In2Se3 assisted Ni-MOL composite bimetallic photocatalyst was assembled, of which could obtain the degradation rate of 96.4% within 90 min for TC under visible light. Ni-MOL was the main active site for TC degradation by photo-induced holes which located at the Ni atom active site during the photocatalytic process. The role of In2Se3 and the element of Ti in Ni-MOL was to assist Ni-MOL by providing more photo-induced carriers and inhibiting carrier recombination. This work makes a contribution to the application of 2D bimetallic photocatalytic in TC degradation.

Selective adsorption behavior of Cd2+ imprinted acrylamide-crosslinked-poly(alginic acid) magnetic polymers: fabrication, characterization, adsorption performance and mechanism.

Poly(acrylamide) grafted and glutaraldehyde-crosslinked alginic acid nano-magnetic adsorbent (AAMA) was prepared by selecting Cd2+ as a template ion. Scanning electron microscope (SEM), thermo-gravimetric analyzer (TGA), vibrating sample magnetometer (VSM) and infrared spectroscopy (IR) were used to characterize the morphology and structure of AAMA. The adsorption of AAMA for different metal ions was compared and the impact of various factors for adsorption of Cd2+ was systematically investigated. These results suggested that the AAMA was the aggregates of Fe3O4 nanoparticles with a diameter of about 50-100 nm and had selectivity for Cd2+ adsorption. The maximum adsorption capacity for Cd2+ is 175 mg/g at pH 5.0 and 303 K. The experimental data were well described by the Langmuir isotherm model and pseudo-second-order model. The parameters of adsorption thermodynamics concluded that the adsorption progress is spontaneous and endothermic in nature. The parameters of adsorption activation energy suggested that there is physical adsorption and chemisorption on the adsorption of metal ions. AAMA could be regenerated by EDTA and still keep 71% adsorption capacity in the fifth consecutive adsorption-regeneration cycle. Therefore, AAMA would be useful as a selective and high adsorption capacity nano-magnetic adsorbent in the removal of Cd2+ from wastewater.

Zn(II), Pb(II), and Cd(II) adsorption from aqueous solution by magnetic silica gel: preparation, characterization, and adsorption.

A novel magnetic silica gel adsorbent (Fe3O4-Si-COOH) was successfully prepared by introducing carboxyl group in situ to improve the performance for Pb(II), Zn(II), and Cd(II) adsorption. Infrared spectroscopy (IR), scanning electron microscope (SEM), transmission electron microscope (TEM), thermo-gravimetric analyzer (TGA), the Brunauer-Emmett-Teller (BET) surface area, X-ray diffraction (XRD), and vibrating sample magnetometer (VSM) characterizations suggested that Fe3O4-Si-COOH has been successfully prepared. The adsorption performance was evaluated by batch experiments with different initial concentrations, ionic strength, contact time, and pH. The adsorption kinetics data followed pseudo-second-order model and exhibited a three-stage intraparticle diffusion mode. Isothermal adsorption equilibrium data were best fitted by the Freundlich model and the adsorption capacity were 155, 110, and 93 mg/g (initial concentration 210 mg/L) for Pb(II), Zn(II), and Cd(II), respectively. The result of X-ray photoelectron spectroscopy (XPS) survey spectrum suggested that the main adsorption mechanism is that the H+ of carboxyl groups exchanged with heavy metal ions in the adsorption processes. In addition, the adsorbed Fe3O4-Si-COOH could be regenerated and the adsorption capacity of reused Fe3O4-Si-COOH could maintain 80.3% after five cycles. Hence, the Fe3O4-Si-COOH could be a kind of potential material for removing Pb(II), Zn(II), and Cd(II) from wastewater. Graphical abstract.

Fe3O4-CS-L: a magnetic core-shell nano adsorbent for highly efficient methyl orange adsorption.

A novel core-shell bio-adsorbent was fabricated by using biological materials for removing methyl orange (MO) from aqueous solution. The structure characteristics results of scanning electron microscopy (SEM), Fourier transform infrared spectrometry (FT-IR), thermo-gravimetric analysis (TGA), vibrating sample magnetometer (VSM), and Brunauer-Emmett-Teller (BET) shows that Fe3O4-CS-L has been successfully prepared. The effects of contact time, pH, temperature and initial concentration were explored. The results suggested pH was a negligible factor in adsorption progress. Kinetic studies showed that the experiment data followed pseudo-second-order model. Boyd mode suggested that external mass transfer showed a rather weak rate control for MO adsorption onto Fe3O4-CS-L. Equilibrium studies showed that isotherm data were the best described by Langmuir model. The maximum adsorption capacity of MO estimated to be 338.98 mg/g at 298 K. Moreover, the adsorption capacity of Fe3O4-CS-L can keep about 74% in the fifth adsorption-regeneration cycle. Thus, the Fe3O4-CS-L could be a kind of promising material for removing MO from wastewater.