This study explored the tunability of a 3-D porous network in a freeze-dried silk fibroin/soursop seed (SF:SS) polymer composite bioadsorbent. Morphological, physical, electronic, and thermal properties were assessed using scanning electron microscopy, the BET N2 adsorption-desorption test, Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric analysis (TGA). A control mechanism of pore opening–closing by tuning the SS fraction in SF:SS composite was found. The porous formation is apparently due to the amount of phytic acid as a natural cross-linker in SS. The result reveals that a large pore radius is formed using only 20% wt of SS in the composite, i.e., SF:SS (4:1), and the fibrous network closes the pore when the SS fraction increases up to 50%, i.e., SF:SS (1:1). The SF:SS (4:1) with the best physical and thermal properties shows an average pore diameter of 39.19 nm, specific surface area of 19.47 m2·g−1, and thermal stability up to ~450 °C. The removal of the organic molecule and the heavy metal was assessed using crystal violet (CV) dye and the Cu2+ adsorption test, respectively. The adsorption isotherm of both CV and Cu2+ on SF:SS (4:1) follows the Freundlich model, and the adsorption kinetic of CV follows the pseudo-first-order model. The adsorption test indicates that physisorption dominates the adsorption of either CV or Cu2+ on the SF:SS composites.
The performance of biological treatment using a downflow hanging sponge reactor as post-treatment of agro-industrial wastewater has been recognized worldwide. However, the effectiveness of the system in treating POME is remain unknown. Therefore, with this background in mind, an anaerobic treatment operated at COD loading rate of 0.4-0.6 kg/m3/day, HRT of 2 hours and input pH of 7.6 was run using a DHS reactor packed with sponge media for the treatment of POME. During the study, the output concentration performances of COD (32-58%), Colour (41-76%), ammoniacal nitrogen (66-92%) and phosphate (54-87%) were recorded. These results indicate comparable performances with the existing biological treatment system. However, it also offered additional credits in-term of fouling and clogging issues, practically as well as lower cost and energy consumption. Thus, it will be great to have a system that is capable to provide a simple technology which is affordable to various industrial scales.
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