Subcritical Water Technology Research Articles

Application of Subcritical Water for Conversion of Macroalgae to Value-Added Materials

Subcritical water technology was used for treatment of Codium fragile (C. fragile) as a model for green macroalgae. Subcritical water reactions were carried out for 10 min at temperatures ranging f...

Extraction of cottonseed oil using subcritical water technology

AbstractThis work represents the extraction of cottonseed oil using subcritical water. The extraction efficiencies of different range temperatures (180–280°C), having mean particle size range from 3 mm to less than 0.5 mm, water:seed ratios of 0.5:1, 1:1, and 2:1, and extraction times in the range of 5–60 min were all investigated. The composition of the extracted oil, using the subcritical water, was analyzed by gas‐liquid chromatography and compared with that extracted using traditional hexane extraction. The results showed that the optimum temperature, mean particle size, water:seed ratio, and extraction time were 270°C, <0.5 mm, 2:1, and 30 min, respectively. In addition the extracted oil was identical to that extracted using the traditional hexane method. © 2010 American Institute of Chemical Engineers AIChE J, 2011

Application of sub-critical water technology for recovery of heavy metal ions from the wastes of Japanese scallop Patinopecten yessoensis

Sub-critical water (sub-CW) technology was used as a new technology with environmental and financial benefits for the recovery of harmful heavy metal ions Cd (II), Zn (II), Cu (II), Fe (II), Mn (II) and Ni (II) in the waste of Japanese scallop Patinopecten yessoensis. The metals are responsible for environmental problems owing to the large amount of the waste. This study proposes a new method using sub-CW treatment to recover the metal ions from scallop waste and simultaneously produce harmless and valuable materials. Reactions were conducted in a temperature range of 473–653 K and for reaction times of 1–60 min. After the sub-CW reaction, four phases existed: an oil phase, metal-soap phase, aqueous phase and solid residual. Some oil was hydrolyzed by the sub-CW reaction and converted to free fatty acids and glycerin. Free fatty acids reacted with metal ions and became metal-soap phase. Both the metal-soap phase and oil phase caught almost all metal ions at low and medium reaction temperatures (473–573 K) from original wastes, although the concentrations of the metal ions in the metal-soap phase were much higher than those in the oil phase. With increasing temperature, these two phases decomposed and the metal ions concentrated in solid residual (un-reacted waste). The binding mechanisms in the oil and metal-soap phases are discussed including the key functional groups involved. The maximum concentrations of metal ions in metal-soap phase were 7225 ppm (Fe), 862 ppm (Zn), and 800 ppm (Cd) at 573 K. The aqueous phase showed the lowest concentration of metal ions especially at temperatures above 550 K (∼ 1.5 ppm).

Mechanical and Thermal Properties of a Novel Protein-Based Plastic Synthesized Using Subcritical Water Technology

This work reports on the characterization of a novel protein-based plastic synthesized from bovine serum albumin (BSA) using subcritical water technology. In the present study, the mechanical and thermal properties of the novel plastic (PBSA) are presented while investigating the effects of blending biodegradable organic compounds on its mechanical properties. The average ultimate tensile strength (UTS) of the processed PBSA samples was 12.7 MPa with a modulus of elasticity (E) and tensile strain at the break () of 370 MPa and 1.7%, respectively. Blending 10% glycerin with PBSA resulted in a reduction in the UTS (10.1 MPa) but increased the value (4.4%). An increase of the glycerin percent to 25% further decreases the UTS (8 MPa) while further increasing (7.8%). The addition of 10% starch resulted in a reduction in both the UTS and (7.3 MPa, 1.3%). Conversely, the PBSA with 25% starch blends showed a dramatic reduction in UTS (0.6 MPa) while increasing the value (2.8%). A scanning electron microscope (SEM) was used to investigate the morphological properties of the tested samples. The SEM images showed a smooth and homogeneous morphology in the glycerin blend and a phase separation in the starch blend.