No abstract

For the first time, an environmentally friendly and effective procedure to produce high-value engineering aerogels from fly ash (FA) has been developed by dispersing FA particles into a mixture of biodegradable polyvinyl alcohol (PVA) and carboxymethyl cellulose (CMC), followed by freezedrying. The effect of FA content on the physical properties, morphology, mechanical strength, and thermal conductivity of FA aerogels is also studied comprehensively. The lightweight FA aerogels show a low density of 0.072 – 0.093 g/cm3 with high porosity of 94.94 – 95.78%. The morphology of aerogels shows the uniform distribution of FA particles in PVA-CMC matrixes that creates a porous structure with a pore size of 2-5 mm. Therefore, the FA aerogels exhibit good heat insulation with extremely low thermal conductivity of 0.040 – 0.047 W/m.K at ambient temperature and pressure that is comparable to some commercial insulation materials such as mineral wool, fiberglass, expanded polystyrene, and other silica-based aerogels from waste. Moreover, the compressive modulus of FA aerogels is about 67.73 – 254.75 kPa indicating their excellent mechanical properties under 1 kN vertical compression. The experimental results indicate the significant better durability of FA aerogels than that of previous aerogels from other wastes such as sugarcane bagasse (88 kPa), pineapple leaf fibers (1.64 – 5.34 kPa), recycled polyethylene terephthalate (1.16 – 2.87 kPa), spent coffee grounds (5.41 – 15.62 kPa), and silica – cellulose (86 – 169 kPa). It is concluded that FA aerogels are a promising candidate as a lightweight thermal insulating material.

Capacitive deionization (CDI) is an electrochemical water treatment process that holds the promise of not only being a commercially viable alternative for treating water but for saving energy as well. Carbon aerogel electrodes for CDI process with high specific surface area (779.04 m2/g) and nano-pore (2-90 nm) have been prepared via pyrolyzing RF organic aerogel at 800oC in nitrogen atmosphere. The CDI characteristics of carbon aerogel electrodes were investigated for the NaCl absorption into a CDI cell at variation conditions. Experiments data showed that the maximum NaCl removal capacity was 21.41 mg/g in 500 mg/L NaCl solution, higher than for other carbon-based materials in the literature. It was evaluated that the CDI process using carbon aerogel electrodes promising to be an effective technology for desalination.

Carbon aerogel was obtained by pyrolysis of organic aerogel by ambient pressure drying technique. The effect of pyrolysis conditions on characteristics of carbon aerogel such as density, specific surface area and conductivity was studied. The properties and structure of carbon aerogel samples were investigated by nitrogen adsorption, four-point probe method and XRD diffraction. The results showed that carbon aerogel had structure between amorphous and graphite state. The highest specific surface area was 800 m2/g at pyrolysis temperature of 700oC. The pore-size was distributed in microporous, with the maximum total pore volume of 0.44 cm3/g. The electrical conductivity of carbon aerogel was highest at pyrolysis temperature of 800-900oC with the value in the range of 1.744-1.923 S/cm.