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In this study, a modified copper ferrite/NiMgAl layered double hydroxide (CuFe2O4/NiMgAl-LDH) composite was developed for the adsorptive removal of oxytetracycline hydrochloride (OTC) antibiotic from aqueous solution. Material characterization by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Fourier transforms infrared spectrum (FTIR) and X-ray photoelectron spectroscopy (XPS) confirms that the resultant material composes of a hexagonal layered doubled hydroxide structure with surficial deposits on CuFe2O4 cubes. The adsorption of OTC onto the prepared materials were studied as a function of solution pH, initial OTC concentration, reaction time and temperature. The OTC adsorption capacities of the prepared materials were as follows: CuFe2O4/NiMgAl-LDH composite > NiMgAl-LDH > CuFe2O4. The adsorption of OTC in the presence of salts like CuSO4, NaHCO3, NaCl were also studied and the results revealed that CuSO4 has a positive effect on OTC adsorption while NaHCO3 and NaCl showed the neutral and antagonistic effect. The results revealed that hydrogen bonding, anionic exchange, and electrostatic forces were mainly involved in the adsorption of OTC onto CuFe2O4/NiMgAl-LDH composite. OTC adsorption followed the pseudo-second-order kinetic model while the adsorption equilibrium data were well fitted to the Langmuir isotherm model with the maximum adsorption capacity of 192 mg/g at 323K. Furthermore, the thermodynamic study revealed that the adsorption process was spontaneous and endothermic. Keywords: Adsorption, CuFe2O4 /NiMgAl-LDH composite, Oxytetracycline, Wastewater

A novel lamellar Al(OH)3/CuMnAl-layered double hydroxide (LDH) nanocomposite was successfully synthesized via the hydrothermal method and tested as a highly efficient adsorbent for the removal of Congo red (CR) dye from aqueous solution. Structural, morphological, and spectroscopic characterization of the Al(OH)3/CuMnAl-LDH nanocomposite were studied by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, photoluminescence (PL) analysis, and UV-visible spectroscopy analysis techniques. The CR dye adsorption performance of the prepared materials increased with an increase in functionality. The adsorption capacity of the Al(OH)3/CuMnAl-LDH nanocomposite (172 mg/g, pH 7, temp 30 °C) was found to be higher than that of pure Al(OH)3 (32 mg/g, pH 7, temp 30 °C) and CuMnAl-LDH (102 mg/g, pH 7, temp 30 °C). The results revealed that anion exchange and hydrogen bonding are mainly responsible for the adsorption of CR onto the Al(OH)3/CuMnAl-LDH nanocomposite. Moreover, the adsorption of CR in the presence of Cu(II) and NaCl salt showed a synergistic and antagonistic effect while the presence of anionic Cr(VI) ions had no significant effect. The adsorption thermodynamics, isotherm, and kinetics modeling analyses were also conducted to study the interactions between CR molecules and the Al(OH)3/CuMnAl-LDH nanocomposite. The adsorption of CR was found to be endothermic and followed by the pseudo-second-order kinetics and the Langmuir adsorption isotherm model. The developed nanocomposite showed excellent potential for treating industrial wastewater.

Adsorption and interaction of pollutant species on surface of the catalyst materials play an important role on the photocatalysis process. Herein, experimental data on the adsorption behavior of 2-chlorophenol (2-CP) onto graphitic pure carbon nitride (C3N4), titania nanotubes (TiO2 NTs) and carbon nitride/titania nanotubes nanocomposite (C3N4/TiO2 NTs) from synthetic wastewater has been summarized. The data on photocatalytic degradation of the 2-CP under both ultraviolet (UV) and visible light irradiation is also presented. This work also evaluates the 2-CP scavenging efficiency of C3N4/TiO2 NTs nanocomposite prepared by calcination of 2 wt.% melamine with TiO2 NTs at 450 °C. The adsorption and photocatalysis experiments were conducted for 180 min at pH 7 with 100 mL solution of 2-CP (40 mg/L) and 0.05 g catalyst material. The acquired data can be valuable to identify the equilibrium time for 2-CP adsorption onto C3N4, TiO2 NTs, and C3N4/TiO2 NTs nanocomposite. Moreover, the obtained data can be useful to identify the suitable light source for the decomposition of 2-CP in the aquatic environment. The evaluated kinetic data might be significant for identifying the adsorption and photocatalysis reaction rate onto the applied catalyst materials. The obtained adsorption and photocatalysis data have been compared with that in literature to identify the adsorption and photocatalysis behavior of 2-CP on numerous catalysts at different experimental conditions.

Various adsorbents including agricultural waste–based adsorbents, nanomaterials and layered double hydroxides have been reviewed for removal of antibiotics from water due to their unique properties. The adsorption mechanism is governed mostly by the affinity of a pollutant to adsorbent materials. However, the main adsorption mechanisms defined in this study for removal of antibiotics are the electrostatic attraction, π–π interaction and hydrogen bonding. The study highlighted the contribution of modification in the adsorption capacity of antibiotics. Some of the most important adsorbents discussed in this review are graphene-based adsorbents, binary layered double hydroxides and magnetic nanoparticles as well as the antibiotics sulfamethoxazole, tetracycline and metronidazole. The key factors for the selection of the suitable materials are the structure, characteristics and other physicochemical parameters such as pH and temperature. However, the most crucial factor is the adsorption capacity. Some of the adsorption kinetics models and isotherms for antibiotic sorption are also highlighted in this study. In addition, the review summarizes the future prospects and recent challenges faced with the adsorption techniques for removal of antibiotics from wastewater. This review will help readers understand the current trend in the adsorptive removal of antibiotics from water.

Pharmaceuticals are emerging pollutants present mainly in industrial and municipal wastewater. Herein, structurally variable binary and ternary metal hydroxides based on copper, manganese, and aluminum were used for the adsorptive scavenging of the oxytetracycline (OTC) antibiotic. A facile hydrothermal method was used for the synthesis of binary CuAl-hydroxide, MnAl-hydroxide, and ternary CuMnAl-hydroxide. Structural and morphological characteristics of the metal hydroxides (MHs) were studied by X-ray diffraction (XRD), Fourier transformed infrared spectrum (FTIR), X-ray photoelectron spectroscopy (XPS) and Scanning electron microscopy (SEM) analysis. The adsorptive removal for OTC was found in the order CuMnAl-hydroxide > CuAl-hydroxide > MnAl-hydroxide. The highest removal of OTC by CuMnAl-hydroxide and CuAl-hydroxide was observed at pH 7 while MnAl-hydroxide showed the optimum adsorption at pH 9. All three materials showed different saturation time and equilibrium concentration for OTC adsorption. The mechanism investigation found that strong electrostatic attraction, hydrogen bonding, and anion exchange were mainly responsible for the removal of the OTC and adsorption process followed the pseudo-second-order kinetic model and equilibrium data was best fitted to the Langmuir isotherm model. The adsorption of OTC was influenced by the presence of Cu (II) and Cr (VI) ions in the aqueous solution due to the competitive adsorption of co-ions. Moreover, the adsorption of OTC was endothermic in nature, and maximum adsorption capacity was found to be 250.07 mg/g at 50 °C.