Electrorheology of polyindole

Polyindole particles were prepared by the oxidative polymerization, where ammonium peroxydisulfate was used as an oxidant at several mole ratios to indole. Prepared spherical micrometre-sized polyindole particles were further used as a dispersed phase in silicone-oil electrorheological (ER) fluids and their rheological behaviour was investigated in the presence and in the absence of an electric field. While different oxidant-to-indole mole ratios did not affect the size and morphology of the particles, their electric and dielectric properties were significantly changed. The highest ER effect was observed for the ER fluid based on the particles with low oxidant-to-indole mole ratio (1:1). Such system exhibited yield stress around 100 Pa at 10 wt% concentration of solid phase. Chain-like structures created upon an application of an electric field were further investigated using an optical microscopy, where significant disparities were found according to electric and dielectric properties of the particles. These findings clearly show that varying mole ratio between the indole and oxidant provides systems with tuneable ER effect. © 2021 Elsevier LtdMinistry of Education, Youth and Sports of the Czech Republic, DKRVO [RP/CPS/2020/003]RP/CPS/2020/003; Ministerstvo Školství, Mládeže a Tělovýchovy, MŠM

Simultaneous Urea and Phosphate Recovery from Synthetic Urine by Electrochemical Stabilization

Urine is a widely available renewable source of nitrogen and phosphorous. The nitrogen in urine is present in the form of urea, which is rapidly hydrolyzed to ammonia and carbonic acid by the urease enzymes occurring in nature. In order to efficiently recover urea, the inhibition of urease must be done, usually by increasing the pH value above 11. This method, however, usually is based on external chemical dosing, limiting the sustainability of the process. In this work, the simultaneous recovery of urea and phosphorous from synthetic urine was aimed at by means of electrochemical pH modulation. Electrochemical cells were constructed and used for urea stabilization from synthetic urine by the in situ formation of OH- ions at the cathode. In addition, phosphorous precipitation with divalent cations (Ca2+, Mg2+) in the course of pH elevation was studied. Electrochemical cells equipped with commercial (Fumasep FKE) and developmental (PSEBS SU) cation exchange membranes (CEM) were used in this study to carry out urea stabilization and simultaneous P-recovery at an applied current density of 60 A m−2. The urea was successfully stabilized for a long time (more than 1 month at room temperature and nearly two months at 4 °C) at a pH of 11.5. In addition, >82% P-recovery could be achieved in the form of precipitate, which was identified as amorphous calcium magnesium phosphate (CMP) by using transmission electron microscopy (TEM)