Synthesis and Grafted NH2-Al/MCM-41 with Amine Functional Groups as Humidity Control Material from Silicon Carbide Sludge and Granite Sludge

Mesoporous Al/MCM-41 was synthesized by extracting silicon carbide sludge and granite sludge as the sources of silicon and aluminum. Different concentrations of aminosilane (2.5, 5, 7.5 vol.%) were used to reflux the grafted NH2-Al/MCM-41 with amine functional groups (NH2-Al/MCM-41). The physical and chemical characteristics were analyzed. The results confirmed that silicon carbide sludge and granite sludge can effectively synthesize Al/MCM-41 with low cost and environmental protection. Reflow grafted amine functional groups can effectively improve the surface properties of NH2-Al/MCM-41. The moisture adsorption and desorption capacity of grafted NH2-Al/MCM-41 with amine functional groups was also studied. Based on moisture adsorption and desorption capacity, the surface properties of NH2-Al/MCM-41 were studied. When 5 vol.% of NH2-Al/MCM-41 amine functional groups is added, the moisture adsorption and desorption capacity is best. When the relative humidity = 95%, the equilibrium moisture content is 39.4 kg/kg, which complies with the standard of Japanese Industrial Standard (JIS A 1475). Therefore, the use of waste derived from the industry to replace expensive commercial materials was simple and environmentally friendly, and the grafted NH2-Al/MCM-41 with amine functional groups can be utilized in multiple applications, particularly as moisture regulation materials in building engineering.

Moisture-induced deformations of wood and shape memory

Wood is known to swell substantially during moisture adsorption and shrink during desorption. These deformations may lead to wood damage in the form of cracking and disjoining of wooden components in e.g. floor or windows. Two swelling mechanisms may be distinguished: reversible swelling/shrinkage and moisture-induced shape memory effect. In the latter, wood is deformed in the wet state and afterward dried under maintained deformation, in order that wood retains its deformed shape even after the removal of the mechanical loading, called fixation. When wood is wetted again, it loses its fixation, partially regains its original shape, called recovery. These two mechanisms have their origin at the nanoscale and are modelled here using atomistic simulation and after upscaled to continuum level allowing finite element modelling. Hysteretic sorption and swelling are explained at nanoscale by the opening and closing of sorption sites in ad-and desorption, where in desorption water molecules preferentially remained bonded at sorption sites. The moisture-induced shape memory is explained by the moisture-induced activation of the interfaces between the reinforcing crystalline cellulose fibres and its matrix at nanoscale, referred to as a molecular switch. Our work aims to highlight that the understanding of sorption-induced reversible deformation and moisture-induced shape memory may play an important role in wood engineering and in building physics applications.

Mechanism of Moisture Adsorption In Plant Fibers Surface-Modified With Glycerol Evaluated By LF-NMR Relaxation Technique

Surface modification by humectants is an important technology to improve product quality in textile field, healthcare, tobacco processing and paper-making industry. As a common humectant glycerol is applied to keep the moisture adsorbability of plant fibers during manufacturing. The effects of glycerol on the moisture adsorption of plant fibers were studied by analysising the induced differences of bulk and surface physicochemical property with XRD, FTIR, SEM characterizations. The improvement of moisture adsorption capacity of the modified plant fibers was due to the increased active adsorption sites, while the moisture diffusion resistance increased simultaneously with glycerol indicated by a declining Deff. LF-NMR relaxation spectra demonstrated the water sates and distributions in plant fibers were changed by loading glycerol. The moisture transfer mechanisms induced by glycerol were also investigated. Free water failed to materialize in the plant fibers treated with glycerol, immobile water existed preferentially during the adsorption, and bound water presented increasing after the immobile water were saturated. These findings are useful to improve the manufacturing processes of moisture-retaining properties of different functional plant fibers.

A Simple Method To Valorize Silica Sludges Into Sustainable Coatings For Indoor Humidity Buffering

In this study, the production of indoor humidity-buffering coatings (IHC-s) from recycling waste silica sludges by using a room-temperature sol-gel method which is a simple and energy-efficient route is reported. The properties of these IHC-s coatings are identified by scanning electron microscope, X-ray diffraction, X-ray fluorescence spectrometer, laser particle size analyzer, N2 adsorption-desorption isotherms and toxicity characteristic leaching procedure (TCLP). The moisture adsorption-desorption tests show that the IHC-s coatings have moisture buffering values of ca. 270-316 g m-2 and moisture contents of 24-27% in the range of 50-90% relative humidity (RH). Furthermore, the humidity buffering capacities, moisture adsorption-desorption rate and stability are significantly superior to commercially available coatings in the range of 50-75% RH. The enhancement may be due to the formation of porous structure in the coatings via the dispersed waste silica sludges and gypsum which transformed from bassanite by self-assembly process. Most importantly, the prepared IHC-s coatings show surpassing antimicrobial efficacy (> 99.99%) and no detectable leaching heavy metals based on TCLP tests, which provides an economic and environmental-friendly route for recovering and valorizing industrial wastes.

Influence of Torrefaction Temperature and Climatic Chamber Operation Time on Hydrophobic Properties of Agri-Food Biomass Investigated Using the EMC Method

Due to the tendency for excessive moisture adsorption by raw, unprocessed biomass, various methods of biomass valorization are in use, allowing for the improvement of physical–chemical biomass properties, including hydrophobicity. One of the methods is torrefaction, which changes the hydrophilic properties of the biomass to hydrophobic. Therefore, in this study, the influence of the torrefaction temperature and the exposure time to moisture adsorption conditions on the hydrophobic properties of waste biomass from the agri-food industry (lemon peel, mandarin peel, grapefruit peel, and butternut-squash peel) were analyzed. The torrefaction was carried out at the following temperatures: 200, 220, 240, 260, 280, 300, and 320 °C. The hydrophobic properties were determined by using the EMC (Equilibrium Moisture Content) method, conducting an experiment in the climatic chamber at atmospheric pressure, a temperature of 25 °C, and relative humidity of 80%. The total residence time of the material in the climate chamber was 24 h. It was shown that the torrefaction process significantly improves the hydrophobic properties of waste biomass. Concerning dried raw (unprocessed) material, the EMC (24 h) coefficient was 0.202 ± 0.004 for lemon peels, 0.223 ± 0.001 for grapefruit peels, 0.237 ± 0.004 for mandarin peels, and 0.232 ± 0.004 for butternut squash, respectively. After the torrefaction process, the EMC value decreased by 24.14–56.96% in relation to the dried raw material, depending on the type of organic waste. However, no correlation between the improvement of hydrophobic properties and increasing the torrefaction temperature was observed. The lowest values of the EMC coefficient were determined for the temperatures of 260 °C (for lemon peel, EMC = 0.108 ± 0.001; for mandarin peel, EMC = 0.102 ± 0.001), 240 °C (for butternut-squash peel, EMC = 0.176 ± 0.002), and 220 °C (for grapefruit peel, EMC = 0.114 ± 0.008). The experiment also showed a significant logarithmic trend in the dependence of the EMC coefficient on the operating time of the climatic chamber. It suggests that there is a limit of water adsorption by the material and that a further increase of the exposure time does not change this balance.