The URL can be used to link to this page

Home My WebLink About01. (Handout) Presentation-Wastewater Microbial Fuel Cells and Photo-assisted Reduction Catalysis Item 1 . (Handout) Wastewater Microbial Fuel Cells and Photo - assisted Reduction Catalysis SRISAI NACHURI GRADE 11 , DOUGHERTY VALLEY HIGH SCHOOL CONTRA COSTA COUNTY SCIENCE AND ENGINEERING FAIR The Global Water Crisis 2. 1 billion people lack access to a clean water supply 4.5 billion people lack safely managed sanitation Much of our freshwater is used industrially and in low income countries, only 8% of wastewater is treated In the United States water treatment is 3-4% of our energy expenditure US electrical costs in water treatment contribute nearly 45 million tons of green house gases M 0 icrobial �'licr��blul Fuel Fell c?rgalllc MI$l�r+ ►4:�t�Y {1s}'ern �� r 'I Fl�ctr�,u hlcrlrwol � �'arl7n�l I ikiFM � FlaFw• `4 �{I�44ii�1` Microbial _ Cells _ an electrochemical redox reaction to _ku�adr �'Athndr; elrclron�+ generate electric current Anaerobic • • • organic �13U{'Ii7�7113{IPCId ifGEF!{. {'hawb{`r {'�awher matter provide electrons Serof-pe ar n�:�blc rnembrae� cleaningthe water e e' MFCs can potentially reduce organic sewage content by 80% before r' • •r wastewatercao�ou i treatmentkr 111 Y� CC, O { rlOC�l:: Bat�eril,rn Membrane Current Drawbacks of MFCs Expensive platinum catalysts in the cathode Low electrical output infeasible for appliances with large energy demands Expensive Proton Exchange Membrane and Salt Bridges are too inefficient Photo assise ReductionCatalysis i 4 1 Certain semiconducting materials have electrons excited when exposed to light Recent research on polymer semiconductors in China Semiconductors can facilitate electron transport in cathode to reduce 02 more efficiently Requires optimal light spectrum in order to excite electrons My Research Part 1 : Wastewater MFC Construction Part 2: Semiconductor Bandgap Construction of a functional MFC Simulation using a wastewater sample Simulation using The Materials Testing for voltage output and Project Simulation tool to look for consistency of current trends in bandgaps of various metal oxides and sulfides Goal: To build a working model of Simulation to find density of states an MFC information for samples Goal: find trends to suggest material design for photocatalyst construction Part 1 : MFC Construction Wastewater obtained was partially treated effluent with added yogurt sample to provided bacterial culture ► Carbon and zinc electrodes Electrode CarbonI ► A capacitor was attached to the electrodes during the testing Water and period to mimic charging a Wastewater and Phosphate Ph Yogurt Buffer battery Part 2 : SeSimulation Harnessing the power of supercamputing and state of the art electronic n � Various compounds were tested: TE_ structure methods,the Materials Project provides open web-based access to computed information on known and predicted materials as well as Materials powerful analysis tools to inspire and design novel materials. Transition metal compounds with oxygen group nonmetals ProjectSign In or lkeglst+r io startusing R Data Collected: Bandgap (eV) Density of States plots (diagram of { electron state density) Taken from The Materials Project (I did not create the tool) Photos OEIVA cn '...+m m $ O CO 0y n c, Results Part I Maximum • • • - • • Capacitor voltage after I hour: 1.� 1.� 1.� pm pm pm am Rm Rm am pm Rm pm pry Tim��aayarrdTim�� Bandgaps of Metal Oxides s s — r 7 Cd _ 45 Q ■Gmup3 ■Gmup3 ■Gmup4 ■Gmup4 ■Group4 ■Gmup5 ■Gmup5 ■Gmup5 ■Gmup6 ■Gmup6 ■Gmup6 4 5 ■Group] ■Gmupp-7--WGmup 7—EGmupS NGroupB ■Gmup8 ■Gmup9 ■Gmup9 ■Group9 ■Gmup10 ■Gmup10 ■Group 10 ■Gmupll ■Gmupll ■Gmupll ■Group 12 ■Gmupl2 ■Gmupl2 ■Gmupl3 ■Group 13 ■Groupl3 ■Gmupl.3 ¢ - 5 ■Group 14 ■Gmupl4 ■Group14 ■Gmupl4 ■Group 14 ■Gmupl5 ■Group LS ■Gmupl5 ■Group 15 ■Group 15 } o W W 3 C r a w rs 2 Ip n u:a 1 a ---—----- 0 � 1 Groups 3-15 of Periodic Table,Color Coordinated for Cation Element —2 —2 Bandgaps of Metal Sulfides 4 ■Group 3 ■Group 3 ■Group 4 _u Group 4 ■Group 4 ■Group 5 ■Group 5 ■Group 5 ■Group 5 — 35 ■Group 6 ■Group 6 ■Group 7 ■Group 7 ■Group 7 ■Group 8 ■Group 8 ■Group 9 It Group 9 --4 —4 —4 4 U 4 ■Graup 9 ■Group 9 ■Group 10 ■Group 10 ■Group 30 ■Group 11 ■Group 11 ■Group 11 ■Group 12 3 - Density of states Density of states Density of states W ■Group 12 ■Group 12 ■Group 13 ■Group 13 ■Group 13 ■Group 13 ■Group 13 ■Group 14 ■Group 14 C 25 ■Graup 14 ■Group 14 ■Graup 14 ■Group 15 ■Group 15 ■Group 15 ■Group 15 ■Group 15 .Q V 2 R 1.5 ■ . m 1 rrl N M r0 N } N S Z LL O N 0 Groups 3-15 of Periodic Table, Color Coordinated for Cation Element Discussion of Part 2 Results Optimal bandgap for visible light is 1 .8-3.1 V Semiconductors based on cations from Groups 3-8 had bandgaps peaking around 2.5-4 eV for oxides and 1 .5 eV for sulfides Semiconductors based on cations from Groups 13- 16 had bandgaps peaking around 6 eV for oxides and 3 eV for sulfides Bandgap decreases down the period for Transition Metals Many sulfides have no band gaps DST lower for elements with cations from group 8+ Conclusions Wastewater is an efficient medium for electroactive microbial growth and be utilized for electrical generation. Wastewater MFC designs can produce enough voltage to power low-voltage devices with a sustainable current. Metal oxides and sulfides based on cations from Groups 48 can potentially be used for photo-assisted reduction catalysis in the anode in order to accelerate the reaction of the MFC. Further Research Construction of semiconductors for validation, testing "dirtier" water, testing other aspects of MFCs