Dyes used by the textile, tannery, and food industries tend to pollute water bodies and must be removed to get clean water. Hydroxyapatite (HAP) was synthesized from eggshells using the wet precipitation process. The as-synthesized HAP was characterized using Fourier Transform Infrared (FTIR) and X-ray powder diffraction (XRD). The synthesized HAP was mixed with three different clays: halloysite (HNT), kaolinite (KAO), and bentonite (BENT). The removal efficiency values of methylene blue (MB) from the data showed that HAP-BENT adsorbents had higher values, followed by HAP-HNT and then HAP-KAO adsorbents. The combined masses of 24 mg, 34.5 mg, and 33 mg (representing 20%, 15%, and 10% of HAP-BENT mass) had average adsorption capacity values of 20.7 mg/g, 17.2 mg/g, and 17.9 mg/g, respectively. For each mass percentage, the adsorption capacity values were found to decrease with adsorbent dosage. The HAP-BENT composites had removal efficiency values of 98.4, 91.9%, and 91.9%, respectively. Adsorption data for the HAP-BENT adsorbents were found to be well described by the Langmuir isotherm model and pseudo-second-order kinetic model. The effect of temperature on adsorption capacity was evaluated and thermodynamical modeling was undertaken. The thermodynamical modeling predicts that based on the value of the change in enthalpy and Gibbs free energy the process was exothermic and spontaneous. This work confirms the potential of HAP-clay composites in removing MB from water.

In this work we propose a facile method of preparing cost-effective clay-metaloxide/metal (CuO/Ag and ZnO/Ag) composite pellets for an efficient water purification technique. Clay, with intrinsic antibacterial activity, served as a membrane support for different metaloxide/Ag nanoparticles (NPs) concentrations (2.5, 5 and 10 wt.%), as the active fillers. The effect of time (24 and 48 h) on the bactericidal activity of these pellets was also monitored. The clay–nanocomposite pellets were characterized using: X-ray diffraction, X-ray fluorescence, scanning electron microscopy, transmission electron microscopy, ultraviolet–visible (UV–Vis) spectrophotometry and nitrogen desorption analysis. The antibacterial activity performance was tested using E. coli and S. aureus strains of ATCC25922 and ATCC25923, respectively, in two aqueous media (nutrient broth and nutrient-free) by the colony-forming unit method. The results showed that the clay-CuO/Ag composite with a bandgap (1.24 eV) exhibited overall best performance under all conditions and time factors of ~100% efficiency in nutrient-free medium for all concentrations and times and 20–40% efficiency in nutrient broth for 24 h. The clay-ZnO/Ag with a bandgap of 2.88 eV showed no bactericidal activity in both media, except for that with 10 wt.% ZnO/Ag which showed 100% efficiency in nutrient-free medium after 24 h. All the synthesized composites showed 100% bactericidal efficiency in nutrient free medium after 48 h. These results indicate that, the clay/metaloxide/Ag could serve as efficient water purification technique, with a potential for large-scale commercialization.

This paper presents the results of an experimental study of the effects of clay mixtures on the mechanical properties of mixed clays with controlled levels of plasticity, prior to the firing of porous ceramic water filters for water filtration. Two clays with well-characterized initial compositions (Iro and Ewuya clays) are mixed with varying proportions to control their plasticity. The mechanical properties of the mixed and fired clays are then studied using a combination of experiments and theoretical models. These include the flexural strength, fracture toughness, Young’s modulus, and thermal shock resistance of fired clay mixtures. The results show that clay mixtures with 45–60 vol.% of Iro clay and 40–55 vol.% Ewuya clay can be used to produce clay composite filters with robust mechanical properties. The thermal shock resistance of a mixed clay filter (containing 50% Iro clay and 50% Ewuya clay) is also explained using a combination of elastic and viscoelastic crack-bridging models. The regimes for effective viscoelastic crack bridging are identified by comparing the relaxation times to the thermal shock durations. The implications of the results are then discussed for the mixing of locally available clays into robust micro- and nanoporous materials for applications in clay ceramic water filters.

Methylene blue dye (MB dye) is a harmful contaminant for wastewater streams of industries and is harmful to human and aquatic life. An ecofriendly sugar templating process was used to generate porous bentonite/polydimethylsiloxane (PB) and porous magnetite nanoparticles/bentonite/polydimethylsiloxane (PBNP) composite absorbents to remove MB dye in this study. During the infiltration of PDMS solution into the sugar template in the vacuum chamber, bentonite and magnetite particles were integrated on the surface of the PDMS, and the porous structure was generated during the leaching out of sugar particles in water. The absorbents were characterized using Fourier infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The absence of the methyl bond at 2924 cm^-1 and phenol bond at 3325 cm^-1 in the FTIR spectra of the formed membrane proves that the food grade sugar was completely removed. The SEM images confirm that porosity was achieved as well as uniform mixing of the in the formation of composite. MB dye was effectively removed from wastewater using the as-prepared composite as absorbent. The removal efficiencies of the composite PBNP and PB were ~91% and ~85%, respectively. The experimental data was applied to pseudo-first-order (PFO) and pseudo-second-order (PSO) kinetic models as well as the Dubinin-Radushkevich, Harkins-Jura, and Elovich models for the adsorption isotherm. The data was found to fit the pseudo-second-order and Elovich models, respectively. The results show that the presence of magnetite nanoparticles improved MB dye removal significantly.

Inorganic nano-metal oxides can be effective alternatives to drug resistant organic antibiotics due to their broad spectrum antimicrobial activity against pathogenic and mutagenic gram-negative and positive bacteria. In this study, zinc and copper oxides (ZnO and CuO) were synthesized using a facile wet chemical method. The oxide nanoparticles were characterized using X-ray diffraction (XRD), UV-Vis spectrometer (UV-Vis), Fourier Transformed Infra-red spectrometer and Transmission electron microscopy (TEM). The antibacterial activities of the nanoparticles were investigated against e. coli and s. aureus using the disk diffusion and microdilution tests. The XRD analysis revealed that both zinc and copper oxide nanoparticles were purely crystalline. The TEM micrographs showed that copper oxide nanoparticles assumed a nanorod shape of average length of 100 nm. Whiles zinc oxide nanoparticles were spherical of average diameter of 15 nm. The FTIR results showed that the nanoparticles were free of impurities and organic surfactants. The optical band gaps of CuO and ZnO according to UV-Vis analysis were respectively 2.63 eV and 3.22 eV. According to the antibacteria tests, the minimum inhibition concentration (MIC) of CuO against e. coli and s. aureus were correspondingly 1mg/ml and 0.25 mg/ml whiles it was 0.1mg/ml for ZnO against s. aureus but ZnO produced no inhibition against e. coli. With the microdilution test, both nanoparticles exhibited activity against both bacteria species at all varying concentrations. CuO had an antibacteria efficiency of 80 to 97% and 85 to 99% for e. coli and s. aureus respectively. The efficiency of ZnO were 20 to 90% and 50 to 89% for e. coli and s. aureus accordingly. The results concluded that CuO had higher antibacteria activity as compared to ZnO.