Fabrication of spirulina based activated carbons for wastewater treatment

The lack of safe drinking water is among the main problems to be faced by many areas of the world due to climate change, unrestrained population increases, and unsustainable usage of water sources. Therefore, research projects focusing on water quality, pollution, and control for sustainable water sources are in high demand to manage any unexpected changes in water sources. Drinking water sources may be contaminated with organic and inorganic chemicals, disinfection by-products, and microorganisms. Different treatment processes to remove these contaminants from water may be limited because of their high costs and time-consuming or require a multiple-barrier approach to improving performance. Therefore, there is a great need to develop an effective process for removing impurities. The primary objective of this study is to assess the effectiveness of algae-based activated carbons and develop a unique, low-cost sustainable process for wastewater treatment. Activated carbons were produced from pelletised algae powder using carbonisation and chemical activation. Chemical activation was carried out with calcium chloride (CaCl2) and zinc chloride (ZnCl2) as chemical agents. Furthermore, Brunauer-Emmett-Teller (BET) along with scanning electron microscopy (SEM) techniques were used to analyse the morphology, surface area, as well as the porosity of the prepared activated carbons to build a water column filter. Based on the results, algae-based carbon with CaCl2 activation provided a better surface area (197.7486 m2/g) and cumulative pore volume (0.105284 cm3/g). The filtration process using algae-based activated carbon can be a promising technique for water treatment with some further improvement and modifications.

Fabrication, Characterization, and In Vitro Cytotoxicity Assessment of Tri-Layered Multifunctional Scaffold for Effective Chronic Wound Healing

Chronic wounds have been a global health risk that demands intensive exploration. A tri-layered biomaterial scaffold has been developed for skin wounds. The top layer of the scaffold is superhydrophobic, and the bottom layer is hydrophilic, both of which were electrospun using recycled expanded polystyrene (EPS) and monofilament fishing line (MFL), respectively. The intermediate layer of the scaffold comprised hydrogel by cross-linking chitosan (CS) with polyethylene glycol. The surface morphology, surface chemistry, thermal degradation, and wettability characteristics of each layer of the scaffold were examined. Also, the antibacterial activity and in vitro cytotoxicity study on the combined tri-layered scaffold were assessed against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Data revealed exceptional water repellency of the heat-treated electrospun top superhydrophobic layer (TSL) with a high-water contact angle (WCA) of 172.44°. A TSL with 15 wt% of micro-/nano-inclusions had the best thermal stability above 400 °C. The bottom hydrophilic layer (BHL) displayed a WCA of 9.91°. Therapeutically, the synergistic effect of the combined tri-layered scaffold significantly inhibited bacteria growth by 70.5% for E. coli and 68.6% for S. aureus. Furthermore, cell viability is enhanced when PEG is included as part of the intermediate CS hydrogel layer (ICHL) composition.

Nanostructured Hybrid Hydrogels for Solar-Driven Clean Water Harvesting from the Atmosphere

The scarcity of useable water is severe and increasing in several regions of the Middle East, Central and Southern Asia, and Northern Africa. However, the earth’s atmosphere contains 37.5 million billion gallons of water in the invisible vapor phase with fast replenishment. The United Nations Convention to Combat Desertification reports that by 2025 about 2.4 billion people will suffer from a lack of access to safe drinking water. Extensive research has been conducted during the last two decades to develop nature-inspired nanotechnology-based atmospheric water-harvesting technology (atmospheric water generator, AWG) to provide clean water to humanity. However, the performance of this technology is humidity sensitive, particularly when the relative humidity (RH) is high (>~80% RH). Moreover, the fundamental design principle of the materials system for harvesting atmospheric water is mostly unknown. In this work, we present a promising technology for solar energy-driven clean water production in arid and semi-arid regions and remote communities. A polymeric electrospun hybrid hydrogel consisting of deliquescent salt (CaCl2) and nanomaterials was fabricated, and the atmospheric water vapor harvesting capacity was measured. The harvested water was easily released from the hydrogel under regular sunlight via the photothermal effect. The experimental tests of this hybrid hydrogel (PAN/AM/graphene/CaCl2) demonstrated the feasibility of around 1.04 L of freshwater production per kilogram of the hydrogel (RH 60%). The synergistic effect enabled by photothermal materials and deliquescent salt in the hydrogel network architecture presents controllable interaction with water molecules, simultaneously realizing efficient water harvesting. This technology requires no additional input of energy. When considering the global environmental challenges and exploring the available technologies, a sustainable clean water supply for households, industry, and agriculture can be achieved from the air using this economical and practical technology.

Polymeric biomaterials for wound healing applications: a comprehensive review

Chronic wounds have been a global health threat over the past few decades, requiring urgent medical and research attention. The factors delaying the wound-healing process include obesity, stress, microbial infection, aging, edema, inadequate nutrition, poor oxygenation, diabetes, and implant complications. Biomaterials are being developed and fabricated to accelerate the healing of chronic wounds, including hydrogels, nanofibrous, composite, foam, spongy, bilayered, and trilayered scaffolds. Some recent advances in biomaterials development for healing both chronic and acute wounds are extensively compiled here. In addition, various properties of biomaterials for wound-healing applications and how they affect their performance are reviewed. Based on the recent literature, trilayered constructs appear to be a convincing candidate for the healing of chronic wounds and complete skin regeneration because they mimic the full thickness of skin: epidermis, dermis, and the hypodermis. This type of scaffold provides a dense superficial layer, a bioactive middle layer, and a porous lower layer to aid the wound-healing process. The hydrophilicity of scaffolds aids cell attachment, cell proliferation, and protein adhesion. Other scaffold characteristics such as porosity, biodegradability, mechanical properties, and gas permeability help with cell accommodation, proliferation, migration, differentiation, and the release of bioactive factors.

Fabrication of hydrophobic PLA filaments for additive manufacturing

There is an ever-greater need for self-cleaning and water-repelling properties of hydrophobic materials at this time in history, mainly due to the coronavirus disease 2019 (COVID-19) pandemic. However, the fabrication processes used to create hydrophobic materials are typically time-consuming and costly. Thus, this study aims to create hydrophobic materials based on low-cost manufacturing. In this study, polylactic acid (PLA) was mixed with various concentrations of hexadecyltrimethoxysilane (HDTMS) and polytetrafluoroethylene (PTFE) with the aid of solvents, chloroform, and acetone, through the solvent casting and melt extrusion process, which is capable of producing hydrophobic PLA filaments suitable for additive manufacturing (AM). Water contact angle (WCA) measurements were performed to verify the improved hydrophobicity of PLA/HDTMS/PTFE filaments. According to the results, it was discovered that the best filament WCAs were achieved with 2 g (10 wt%) of PLA, 0.2 ml of HDTMS, and 1 ml of PTFE (2 g PLA + 0.2 ml HDTMS + 1 ml PTFE), producing an average WCA of 131.6° and the highest WCA of 132.7°. These results indicate that adding HDTMS and PTFE to PLA significantly enhances filament hydrophobicity. Additionally, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA) techniques were utilized to characterize the surface morphology, molecular interactions, and thermal decompositions of the prepared PLA/HDTMS/PTFE filaments. This study revealed that compared to 2 g of pure PLA filament, HDTMS and PTFE altered the microstructure of the filament. Its thermal degradation temperature was impacted, but the melting temperature was not. Therefore, the PLA/HDTMS/PTFE filament is good enough to be printed by the fused filament fabrication (FFF) AM process.

Integrating Spirulina platensis cultivation and aerobic composting exhaust for carbon mitigation and biomass production

Aerobic composting is an effective way to dispose of organic waste. However, considerable carbon is converted into CO₂ and emitted into the atmosphere, which is a waste of the carbon resource and has the potential for the greenhouse gas effect. In this study, an innovative approach coupling aerobic composting exhaust and Spirulina platensis cultivation has been proposed and investigated, resulting in a double-edged solution to mitigating waste and co-generating biomass with a minimal cost of CO₂ supplied in the culture. Experimental results showed that the maximum biomass productivity ranged from 56.61 to 58.38 mg·L^-1·day^-1 was achieved using aerobic composting exhaust as a carbon source. Moreover, the CO₂ fixation rates of 46.36 mg·L^-1·day^-1 and 76.81 mg·L^-1·day^-1 were obtained by S. platensis cultivation. Finally, the chemical composition analysis of S. platensis biomass obtained in an optimum condition showed an abundance of proteins and lipids, thereby indicating its great potential for biofuel industry.