Phosphorus removal is essential to avoid eutrophication in water bodies. Layered double hydroxides (LDHs) are widely used to scavenge phosphate through intercalated ion exchange or surface complexation. Moreover, LDHs have attracted increasing attention as electrode modifiers for supercapacitors. Researchers have begun to re-delve the electrosorption technology according to the fundamental principle of electrical double layers. Herein, we propose a new phosphate removal method inspired by the adsorption characteristic and electrical double-layer capacitive properties of LDHs through electrosorption via capacitive deionization. We present a series of experiments to study the enhanced phosphate removal under an electric field via multiple mechanisms on the MgAl-LDHs/AC electrode. The uptake of phosphate by MgAl-LDHs/AC was investigated as a function of phosphate concentration, applied voltage, electrode materials, and temperature. The MgAl-LDHs/AC electrode possessed a salt removal capacity of 67.92 mg PO4 3-•g-1 (1.2 V, 250 mg•L-1 KH2PO4, 30 °C). The electrosorption kinetics of phosphate ions onto the capacitive deionization electrode followed the pseudo-second-order kinetics model rather than the pseudo-first-order kinetics model. Furthermore, the adsorption isotherms of phosphate on the MgAl-LDHs/AC electrode fitted the Freundlich model better than the Langmuir model. The proposed method could be used for phosphate removal.
In Acetone-Butanol-Ethanol fermentation, bacteria should tolerate high concentrations of solvent products, which inhibit bacteria growth and limit further increase of solvents to more than 20 g/L. Moreover, this limited solvent concentration significantly increases the cost of solvent separation through traditional approaches. In this study, alginate adsorbent immobilization technique was successfully developed to assist in situ extraction using octanol which is effective in extracting butanol but presents strong toxic effect to bacteria. The adsorbent improved solvent tolerance of Clostridium acetobutylicum under extreme condition of high concentration of organic solvent. Using the developed technique, more than 42% of added bacteria can be adsorbed to the adsorbent. Surface area of the adsorbent was more than 10 times greater than sodium alginate. Scanning electron microscope image shows that an abundant amount of pore structure was successfully developed on adsorbents, promoting bacteria adsorption. In adsorbent assisted ABE fermentation, there was 21.64 g/L butanol in extracting layer compared to negligible butanol produced with only the extractant but without the adsorbent, for the reason that adsorbent can reduce damaging exposure of C. acetobutylicum to octanol. The strategy can improve total butanol production with respect to traditional culture approach by more than 2.5 fold and save energy for subsequent butanol recovery, which effects can potentially make the biobutanol production more economically practical.
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