Noradiba Nordin

Role of macrophyte and effect of supplementary aeration in up-flow constructed wetland-microbial fuel cell for simultaneous wastewater treatment and energy recovery

This study investigates the role of plant (Elodea nuttallii) and effect of supplementary aeration on wastewater treatment and bioelectricity generation in an up-flow constructed wetland-microbial fuel cell (UFCW-MFC). Aeration rates were varied from 1900 to 0mL/min and a control reactor was operated without supplementary aeration. 600mL/min was the optimum aeration flow rate to achieve highest energy recovery as the oxygen was sufficient to use as terminal electron acceptor for electrical current generation. The maximum voltage output, power density, normalized energy recovery and Coulombic efficiency were 545.77±25mV, 184.75±7.50mW/m3, 204.49W/kg COD, 1.29W/m3 and 10.28%, respectively. The variation of aeration flow rates influenced the NO3- and NH4+ removal differently as nitrification and denitrification involved conflicting requirement. In terms of wastewater treatment performance, at 60mL/min aeration rate, UFCW-MFC achieved 50 and 81% of NO3- and NH4+ removal, respectively. E. nuttallii enhanced nitrification by 17% and significantly contributed to bioelectricity generation.

Microbial fuel cell operation using monoazo and diazo dyes as terminal electron acceptor for simultaneous decolourisation and bioelectricity generation.

Monoazo and diazo dyes [New coccine (NC), Acid orange 7 (AO7), Reactive red 120 (RR120) and Reactive green 19 (RG19)] were employed as electron acceptors in the abiotic cathode of microbial fuel cell. The electrons and protons generated from microbial organic oxidation at the anode which were utilized for electrochemical azo dye reduction at the cathodic chamber was successfully demonstrated. When NC was employed as the electron acceptor, the chemical oxygen demand (COD) removal and dye decolourisation efficiencies obtained at the anodic and cathodic chamber were 73±3% and 95.1±1.1%, respectively. This study demonstrated that the decolourisation rates of monoazo dyes were ∼50% higher than diazo dyes. The maximum power density in relation to NC decolourisation was 20.64mW/m2, corresponding to current density of 120.24mA/m2. The decolourisation rate and power output of different azo dyes were in the order of NC>AO7>RR120>RG19. The findings revealed that the structure of dye influenced the decolourisation and power performance of MFC. Azo dye with electron-withdrawing group at para substituent to azo bond would draw electrons from azo bond; hence the azo dye became more electrophilic and more favourable for dye reduction.

Elucidating the effects of different photoanode materials on electricity generation and dye degradation in a sustainable hybrid system of photocatalytic fuel cell and peroxi-coagulation process

The hybrid system of photocatalytic fuel cell - peroxi-coagulation (PFC-PC) is a sustainable and green technology to degrade organic pollutants and generate electricity simultaneously. In this study, three different types of photocatalysts: TiO2, ZnO and α-Fe2O3 were immobilized respectively on carbon cloth (CC), and applied as photoanodes in the photocatalytic fuel cell of this hybrid system. Photocatalytic fuel cell was employed to drive a peroxi-coagulation process by generating the external voltage accompanying with degrading organic pollutants under UV light irradiation. The degradation efficiency of Amaranth dye and power output in the hybrid system of PFC-PC were evaluated by applying different photoanode materials fabricated in this study. In addition, the effect of light on the photocurrent of three different photoanode materials was investigated. In the absence of light, the reduction of photocurrent percentage was found to be 69.7%, 17.3% and 93.2% in TiO2/CC, ZnO/CC and α-Fe2O3/CC photoanodes, respectively. A maximum power density (1.17 mWcm-2) and degradation of dye (93.8%) at PFC reactor were achieved by using ZnO/CC as photoanode. However, the different photoanode materials at PFC showed insignificant difference in dye degradation trend in the PC reactor. Meanwhile, the degradation trend of Amaranth at PFC reactor was influenced by the recombination rate, electron mobility and band gap energy of photocatalyst among different photoanode materials.

Exploring the relationship between molecular structure of dyes and light sources for photodegradation and electricity generation in photocatalytic fuel cell

Reactive green 19, acid orange 7 and methylene blue are employed as the organic pollutants in this work. A photocatalytic fuel cell is constructed based on the idea of immobilizing zinc oxide onto zinc photoanode and platinum loaded carbon cathode, both evaluated under sunlight and ultraviolet irradiation, respectively. Influence of light and dye structures on the performance of photocatalytic fuel cell are examined. With reactive green 19, 93% and 86% of color removal are achieved after 8 h of photocatalytic fuel cell treatment under sunlight and ultraviolet irradiation, respectively. The decolorization rate of diazo reactive green 19 is higher than acid orange 7 (monoazo dye) when both dyes are treated by photocatalytic fuel cell under sunlight and ultraviolet irradiation, as the electron releasing groups (-NH-triazine) allow reactive green 19 easier to be oxidized. Comparatively, acid orange 7 is less favorable to be oxidized. The degradation of methylene blue is enhanced under sunlight irradiation due to the occurrence of self-sensitized photodegradation. When methylene blue is employed in the photocatalytic fuel cell under sunlight irradiation, the short circuit current (0.0129 mA cm-2) and maximum power density (0.0032 mW cm-2) of photocatalytic fuel cell greatly improved.

Up-flow constructed wetland-microbial fuel cell for azo dye, saline, nitrate remediation and bioelectricity generation: From waste to energy approach

This study explored the influence of azo dye concentration, salinity (with and without aeration) and nitrate concentration on bioelectricity generation and treatment performance in the up-flow constructed wetland-microbial fuel cell (UFCW-MFC) system. The decolourisation efficiencies were up to 91% for 500 mg/L of Acid Red 18 (AR18). However, the power density declined with the increment in azo dye concentration. The results suggest that the combination of salinity and aeration at an optimum level improved the power performance. The highest power density achieved was 8.67 mW/m2. The increase of nitrate by 3-fold led to decrease in decolourisation and power density of the system. The findings revealed that the electron acceptors (AR18, nitrate and anode) competed at the anodic region for electrons and the electron transfer pathways would directly influence the treatment and power performance of UFCW-MFC. The planted UFCW-MFC significantly outweighed the plant-free control in power performance.