Upcycling of Wastewater Sludge Incineration Ash as a 3D Printing Technology Resource

Recycling of usable resources from waste must be prioritized to adhere to the circular economy policy implemented worldwide. This study aims to use wastewater sludge incineration ash (WSIA), which is a by-product of wastewater sludge treatment processes, in the 3D printing industry as a sustainable material. First, we explored the stability of incinerated ash generated from a wastewater treatment facility in Seoul by evaluating its physical (water content, organic matter content, and particle size) and chemical (oxide compound composition) characteristics. Composition ratios of the predominant oxides of silicon (SiO2), aluminum (Al2O3), phosphorous (P2O5), iron (Fe2O3), and calcium (CaO) were stable for 6 months. This finding indicates the potential for the incinerated ash to be commercially viable as a powder-bed 3D printed geopolymer. We then examined the optimal ratio of admixtures between the incinerated ash and ultrarapid hardening cement and the following post-treatment process method as a curing stage. The composite material made with 25% WSIA exhibited stability during the curing stage using alkaline solutions, and its compressive strength and water absorption were in accordance with the values recommended by the Korean Standard for decorative concrete blocks (KS F 4038). Additionally, a geopolymer prototype with 25% incinerated ash was produced. To support efficient upcycling of WSIA, long-term environmental and functional monitoring of the final product, effects of incinerated ash particle sizes, and post-treatment process times were further investigated to reduce costs.

Milled Surface Integrity: Application to Fixed Dental Prosthesis

Surface integrity is a multiphysics (biological, mechanical, optical, chemical, esthetic, etc.) and multiscale (from nm to mm) concept. It is defined as the residual signature left on the surface by the manufacturing or post-treatment process and permits correlating the process with the expected surface functionalities. Thanks to the advances made in mechanical engineering, the concept of surface integrity has been transposed to dentistry and oral science. The surface integrity concept transposed to fixed dental prostheses is presented in this article. The main components of surface integrity and their correlations within the triptych of surface integrity–process–clinical functionalities are presented.

Synthesis of self-assembled hierarchical AlPO-34 microspheres by using an ionic liquid and its application in heavy metal removal

Hierarchical AlPO-34 molecular sieves microspheres were synthesized in a [BMIm]Br ionic liquid without template or complex post-treatment process. The formation mechanism of such framework structures and their morphology were investigated. [BMIm]Br was proven to serve as both solvent and sole provider of the structure directing agent. The organic amine in the compound affects the framework density of the crystals and promotes the formation of a chabazite (CHA) type framework. After ageing for 1 h the AlPO-34 microspheres are formed due to the aggregation properties of the ionic liquid. The hierarchical mirosphere has a relatively high Brunauer–Emmett–Teller surface area and a considerably uniform mesoporous channel network. The hierarchical AlPO-34 microspheres were used as absorbers of heavy metal cations and showed a higher loading capacity and distribution coefficient compared with the AlPO-34-NH.

Effects of Different Post-Treatments on Arc Erosion Resistance of Cold-Sprayed AgC Composite Electric Contact

Graphite-silver (AgC) composite materials are widely used in outdoor high-voltage electrical switchgear due to their combining properties of excellent conductivity and outstanding arc-suppressing performance. However, the methods for fabricating AgC composite materials still have some limitations. In this study, the cold spray technique was adopted to deposit AgC composite coatings with the optimized parameters on the copper substrate. Then, AgC coatings were annealed in the furnace and treated by laser scanning, respectively, to further improve the arc erosion resistance performance of the coatings. The results show that the phase structure and electrical resistance of AgC coatings were not influenced by the post-treatment process. Furthermore, excellent hydrophobic performance was obtained after surface laser scanning treatment. The laser scanning treatment exhibited favorable advantages in enhancing the arc erosion resistance of AgC coatings, which indicated the lowest arc erosion rate compared with the cold-sprayed and annealed coatings.

Facile fabrication and characterization of aliphatic polyketone (PK) micro/nano fiber membranes via electrospinning and a post treatment process

In this article, polyketone (PK) micro/nano fiber membranes were successfully fabricated by electrospinning and a post treatment process and the membrane characteristics were investigated.

Effect of post-treatment process of microalgal hydrolysate on bioethanol production

Microalgae accumulate abundant lipids and are a promising source for biodiesel. However, carbohydrates account for 40% of microalgal biomass, an important consideration when using them for the economically feasible production of biodiesel. In this study, different acid hydrolysis and post-treatment processing of Chlorella sp. ABC-001 was performed, and the effect of these different hydrolysates on bioethanol yield by Saccharomyces cerevisiae KL17 was evaluated. For hydrolysis using H2SO4, the neutralization using Ca(OH)2 led to a higher yield (0.43 g ethanol/g sugars) than NaOH (0.27 g ethanol/g sugars). Application of electrodialysis to the H2SO4 + NaOH hydrolysate increased the yield to 0.35 g ethanol/g sugars, and K+ supplementation further enhanced the yield to 0.41 g ethanol/g sugars. Hydrolysis using HNO3 led to the generation of reactive species. Neutralization using only NaOH yielded 0.02 g ethanol/g sugars, and electrodialysis provided only a slight enhancement (0.06 g ethanol/g sugars). However, lowering the levels of reactive species further increased the yield to 0.25 g ethanol/g sugars, and K+ supplementation increased the yield to 0.35 g ethanol/g sugars. Overall, hydrolysis using H2SO4 + Ca(OH)2 provided the highest ethanol yield, and the yield was almost same as from conventional medium. This research emphasizes the importance of post-treatment processing that is modified for the species or strains used for bioethanol fermentation.