The desalination of inland brackish groundwater offers the opportunity to provide potable drinking water to residents and industrial cooling water to industries located in arid regions. Geothermal brines are used to generate electricity, but often contain high concentrations of dissolved salt. Here, we demonstrate how the residual heat left in spent geothermal brines can be used to drive a membrane distillation (MD) process and recover desalinated water. Porous polypropylene membranes were coated with a carbon nanotube (CNT)/poly(vinyl alcohol) layer, resulting in composite membranes having a binary structure that combines the hydrophobic properties critical for MD with the hydrophilic and conductive properties of the CNTs. We demonstrate that the addition of the CNT layer increases membrane flux due to enhanced heat transport from the bulk feed to the membrane surface, a result of CNT's high thermal transport properties. Furthermore, we show how hydroxide ion generation, driven by water electrolysis on the electrically conducting membrane surface, can be used to efficiently dissolve silicate scaling that developed during the process of desalinating the geothermal brine, negating the need for chemical cleaning.
Two kinds of 3-alkoxythiophene monomers were synthesized by the nucleophilic substitution and transetherification reactions. Soluble conjugated polymers based on 3-alkoxythiophene were synthesized by electrochemical polymerization. The process of the electrochemical polymerization, electrochemical redox behaviors and electrochromis of the polymer were investigated by the cyclic voltammetry and spectroelectrochemical measurement. The onset oxidation potentials (Eonset(ox)) of both POT and OOT were at 1040mV (vs. Ag/AgCl) in electrolyte solution system.The oxidation and reduction potential of PPOT and POOT were observed between +600 mV and +900mV (vs. Ag/AgCl). The color of POOT film on the platinum electrode was blue-green for oxidation state and was dark red for reduction state, in accordance with the UV-vis spectra behaviors.
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