• Energy Research

Microbial fuel cells (MFCs) are a novel technique for converting biodegradable materials into electricity. In this study, the efficiency of mixed crystal (TiO2:ZnO) as a membrane modifier of a low-cost, antifouling and self-cleaning cation exchange membrane for MFCs was studied. The modification was prepared using polydopamine (PDA) as the bio-inspired glue, followed by gravity deposition of a mixture of catalyst nanoparticles (TiO2:ZnO 0.03%, 1:1 ratio) as anti-biofouling agents. The effects of the membrane modification were evaluated in terms of power density, open circuit potential, coulombic efficiency, anti-biofouling properties and also color and COD removal efficiency. The results showed that the use of the PDA-modified membrane and a mixture of catalysts facilitated the transfer of cations released during the oxidation process in the anodic compartment of the MFC, which increased the power generation in the MFC by 2.5 times and 5.7 times the current compared to pristine and PDA pristine membranes, decreased the MFC operating cycle time from 5 to 3 days, doubled the lifetime of the membranes and demonstrated higher COD removal efficiency and color removal. Finally, SEM and AFM analysis showed that the modification significantly minimized surface fouling. The modified membranes in this study proved to be a potential alternative to the expensive membranes currently used in MFCs, furthermore, this modification could be an interesting alternative modification for other potential membranes for use in MFCs, due to the fact that the catalyst activation was only performed with visible light (artificial and solar), which could decrease operating costs.

A new crystallization process for sodium bicarbonate (NaHCO3) was studied, proposing the use of osmotic membrane distillation crystallization. Crystallization takes place due to the saturation of the feed solution after water evaporation on the feed side, permeating through the membrane pores to the osmotic side. The process operational parameters, i.e., feed and osmotic velocities, feed concentration, and temperature were studied to determine the optimal operating conditions. Regarding the feed and osmotic velocities, values of 0.038 and 0.0101 m/s, respectively, showed the highest transmembrane flux, i.e., 4.4 × 10−8 m3/m2·s. Moreover, study of the temperature variation illustrated that higher temperatures have a positive effect on the size and purity of the obtained crystals. The purity of the crystals obtained varied from 96.4 to 100% In addition, the flux changed from 2 × 10−8 to 7 × 10−8 m3/m2·s with an increase in temperature from 15 to 40 °C. However, due to heat exchange between the feed and the osmotic solutions, the energy loss in osmotic membrane distillation crystallization is higher at higher temperatures.

Every year the demand for energy worldwide is increasing. There are some alternatives to reduce these problems, such as clean energy or renewable energy. A particular alternative is the microbial fuel cells. These cells are biochemical reactors that convert chemical energy into electricity. The present research evaluated the dairy serum to produce bioelectricity from micro fuel cells (MFC) that were constructed with low-cost materials and with isolated bacteria in anaerobic sediments, located in Ecuadorian national territory, producing maximum voltages of 0.830 V in the circuit and a maximum power density of 30mW / m2. This low voltage was worked with 50 mL MFCs and with an output voltage of 300 mV. Under these conditions, a FLYBACK lift circuit isolated by the transformer was designed. This new circuit could increase the voltage from 30 mV to enough voltage to light a 2.5 V LED. Therefore, the energy produced by the MFC can be directly used to light a LED and to charge capacitors. This study shows that these MFCs, together with the designed circuit, could be used potentially to generate clean energy.