Au nanoparticles loaded Hydroxyapatite catalyst prepared from waste eggshell: synthesis, characterization and application in VOC removal

Eggshell, which is made almost entirely of calcium carbonate, is among the most abundant waste materials from poultry production. In 2018, the worldwide egg production exceeded 78 million metric tons which contributed to over 8 million metric tons of eggshell waste. However, this waste can be converted into useful materials for several industrial applications. Herein, hydroxyapatite (HAp) of fine particles was prepared using a green synthesis procedure in water medium from eggshell waste. Then, HAp was utilized as support material for loading different contents of Au nanoparticles (0.2 and 0.5 wt%). The materials were characterized by Brunauer-Emmett-Teller (BET) surface area analysis, Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS), X-ray diffraction (XRD). The prepared catalysts were used for VOCs oxidation of formaldehyde in continuous flow and humid condition. In this study, Au/HAp (0.2 wt%) exhibited superior catalytic activity with good low-temperature reproducibility and high dispersion of particles on the surface of hydroxyapatite. Hence, hydroxyapatite prepared from eggshell waste is considered as a promising support material for noble metal catalysts for VOCs oxidation.

A Comparative Study of the Effect of Graphene Oxide, Graphitic Carbon Nitride, and Their Composite on the Photocatalytic Activity of Cu3SnS4

Photocatalysis has shown high potential in dealing with the ever-broadening problem of wastewater treatment, escalated by the increasing level of recalcitrant chemicals often referred to as emerging contaminants. In this study, the effect of support material on the photocatalytic activity of copper tin sulfide (Cu3SnS4) nanoparticles for the degradation of tetracycline as an emerging contaminant is presented. Graphene oxide, protonated graphitic carbon nitride, and a composite of graphitic carbon nitride and graphene oxide were explored as support materials for Cu3SnS4 nanoparticles. The nanoparticles were incorporated with the different carbonaceous substrates to afford graphene-supported Cu3SnS4 (GO-CTS), protonated graphitic carbon nitride-supported Cu3SnS4 (PCN-CTS), and graphene oxide/protonated graphitic carbon nitride-supported Cu3SnS4 (GO/PCN-CTS). Physicochemical, structural, and optical properties of the prepared nanocomposites were characterized using techniques such as Fourier transform infra-red spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-Vis near infrared, and fluorescence spectrophotometry. The compositing of the Cu3SnS4 nanoparticles on the support materials was confirmed by the characterization techniques, and the optical properties of the composites were found to be influenced by the nature of the support material. The incorporation of CTS into the support materials resulted in a reduction in band gap energy with evaluated band gaps of 1.65, 1.46, 1.43 eV, and 1.16 eV. The reduction in band gap energy suggests the potential of the composites for enhanced photocatalytic activity. From the photocatalytic study, the degradation efficiency of tetracycline by CTS, PCN-CTS, GO-CTS, and PC/GO-CTS was 74.1, 85.2, 90.9, and 96.5%, respectively. All the composites showed enhanced activity compared to pristine CTS, and the existence of a synergy between GO and PCN when both were employed as support materials was observed. Based on the charge carrier recombination characteristics and the band edge potential calculations from the composites, a possible mechanism of action of each composite was proposed. This study therefore confirms the possibility of modulating the mechanism of action and subsequently the efficiency of semiconductor materials by altering the nature of the support material.

Experimental and Analytical Investigations on Tribological Properties of PTFE/AP Composites

The tribological properties of polytetrafluoroethylene (PTFE)/AP (poly(para-phenyleneterephthalamide) (PPTA) pulp) composites under different test conditions (load: 2N, 10N; frequency: 1 Hz, 4 Hz; amplitude: 2 mm, 8 mm) were holistically evaluated. PTFE/AP composites with different AP mass ratios of 3%, 6%, and 12% as a skeleton support material were prepared. The coefficient of friction (COF) and wear rate were determined on a ball-on-disk tribometer. Furthermore, the morphology, element composition, and chemical structure of the transfer membrane were analyzed accordingly. The relationships between load, frequency, amplitude, and tribological properties were further investigated. According to the wear mechanism, AP enables effective improvement in the stiffness and wear resistance, which is also conducive to the formation of transfer films.

Greenhouse cultivation of Serrano Pepper (Capsicum annuum var. acuminatum): Dry Hydroponics

Objective: To produce Serrano peppers using a new cultivation technique that mixes the best of hydroponic cultivation and traditional cultivation. Design/methodology/approach: We set up a growing system where the Serrano pepper grew from seedling to its full-fledged state, in a growbag containing sand (as support material), potassium polyacrylate (as water retention material), and a nutrient solution for vegetable gardens, under greenhouse conditions. The humidity level of the growbag is controlled by adding as much water with nutrient solution as needed. This technique has generated 100% harvestable plants (total: 20 plants); more than 90% of the water can be saved in comparison to regular and hydroponic cultivation. Results: Once the harvest began, at least 22.857 kg of Serrano pepper were obtained in 3 m2 of soil in a system with a pyramidal structure in which the 20 plants were placed. If we extrapolated this data, approximately 93,000 kg of Serrano pepper could be harvested from a 1 ha system. Study Limitations/implications: This technique tries to tackle the water access limitations that may exist in some areas of Mexico. However, it does not mitigate the initial costs of a greenhouse system. Nevertheless, this technique can be reused up to 10 times without requiring maintenance. Findings/conclusions: Experience has shown that hydroponic crops are truly profitable, despite their vast water requirements, which is precisely what prevents their global expansion. However, our modification of this method saves more than 90% of the water, using potassium polyacrylate as a retention agent and sand as a support material. Therefore, this technique could be implemented even in places where water is scarce

A Novel Additive Manufacturing Method of Cellulose Gel

Screen-additive manufacturing (SAM) is a potential method for producing small intricate parts without waste generation, offering minimal production cost. A wide range of materials, including gels, can be shaped using this method. A gel material is composed of a three-dimensional cross-linked polymer or colloidal network immersed in a fluid, known as hydrogel when its main constituent fluid is water. Hydrogels are capable of absorbing and retaining large amounts of water. Cellulose gel is among the materials that can form hydrogels and, as shown in this work, has the required properties to be directly SAM, including shear thinning and formation of post-shearing gel structure. In this study, we present the developed method of SAM for the fabrication of complex-shaped cellulose gel and examine whether successive printing layers can be completed without delamination. In addition, we evaluated cellulose SAM without the need for support material. Design of Experiments (DoE) was applied to optimize the SAM settings for printing the novel cellulose-based gel structure. The optimum print settings were then used to print a periodic structure with micro features and without the need for support material.

Study of Influential Factors on the Dielectric Strength of [UPE/BaTiO3] Nanocomposites

Unsaturated polyester resin (UPE) was used as a base material and barium titanite nanoparticles (BaTiO3) (50-7-nm) as a support material, with different weight ratios (0.25,0.75,1.25,2 wt%), to prepare a nanocomposite material. The research models were prepared according to the standard specifications and with different thicknesses (≈ 1.1,1.8,2.2,2.7 mm) to show the effect of thickness, number of cycles, percentage of addition and voltage rise rate at (5 kv/s and 0.5 kv/s) on the dielectric strength (Ebr) of the prepared material. The results showed that Ebr decreased with increasing the thickness of the material, BaTiO3 additive rate and the number of cycles. Dielectric strength (Ebr) increases with increasing of voltage rise rate.