# Performance of the Dual-Chamber Fungal Fuel Cell in Treating Tannery Wastewater
## 4 Conclusions  
In the present study, tannery effluents were subjected to treatment using FFCs for organic degradation and energy production. The genus _Aspergillus_ represents 40% of the total genera present in tannery wastewater. _A. niger_, which had been subjected to hexavalent chromium stress in the training method, had a faster growth rate (\(\upmu\)) about 7.3 \(\pm\) 2.7 mg \(\times\) h\({}^{-1}\) and a high hexavalent chromium removal efficiency, reaching 81.8% compared with the control strain. Freundlich and Koble-Corrigan isothermal adsorption models can adequately explain the sorption of hexavalent chromium in both the trained and the control strains. For 165 h of operation, FFC electrolytic matrices showed high energy output represented in output cell voltage output (V), power density (PD), and current density (CD) due to the lower internal resistance compared to the non-electrolytic FFCs. The maximum power output occurred at 15 h of operation, then decreased gradually due to the cell substrate depletion. The electrolytic FFCs also showed high removal efficiencies that reached 77.9%, 94.2%, and 73.0%, in the case of COD, TN, and total chromium, respectively, compared to the non-electrolytic FFC. According to the findings of using FFCs, the trained _A. niger_ strain increased the sorption ratio of total chromium and increased the fungal growth rate. Using electrolytic matrices increased the FFC performance that was represented by high energy production and high removal efficiency. Further studies are recommended for the evaluation of post-treatment and disposal of Cr-adsorbed fungal strains as a final bio-waste product.  
The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app131910710/s1](https://www.mdpi.com/article/10.3390/app131910710/s1)]([https://www.mdpi.com/article/10.3390/app131910710/s1](https://www.mdpi.com/article/10.3390/app131910710/s1)), Figure S1: Electrolytic and non-electrolytic FFCs treatment performance of COD; Figure S2: Electrolytic and non-electrolytic FFCs treatment performance of Cr; Figure S3: Electrolytic and non-electrolytic FFCs treatment performance of TN.  
Conceptualization, M.S.M., J.-H.W., Y.S., Z.-W.G., A.S.M. and M.K.M.; data curation, M.S.M., J.-H.W., Y.S., Z.-W.G., A.S.M. and M.K.M.; formal analysis, M.S.M., J.-H.W., Y.S., Z.-W.G., A.S.M., M.K.M., R.W.P. and D.-C.Z.; funding acquisition M.S.M., J.-H.W., Y.S. and Z.-W.G.; investigation, M.S.M., J.-H.W., Y.S., Z.-W.G., A.S.M., M.K.M. and R.W.P.; methodology, M.S.M., J.-H.W., Y.S., Z.-W.G., A.S.M., M.K.M. and D.-C.Z.; project administration, M.S.M., J.-H.W., Y.S., Z.-W.G. and Y.Y.; software, M.S.M., J.-H.W., Y.S., Z.-W.G., A.S.M. and M.K.M.; supervision, M.S.M., J.-H.W., Y.S. and Z.-W.G.; validation, M.S.M., J.-H.W., Y.S., Z.-W.G., A.S.M. and M.K.M.; visualization, M.S.M., J.-H.W., Y.S., Z.-W.G., A.S.M., M.K.M., R.W.P., D.-C.Z. and Y.Y.; writing--original draft, M.S.M., J.-H.W., Y.S., Z.-W.G., A.S.M. and M.K.M.; writing--review and editing, M.S.M., J.-H.W., Y.S., Z.-W.G., A.S.M., M.K.M., R.W.P. and Y.Y. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Talented Young Scientists Program (Egypt-19-069), the Innovation Group of New Technologies for Industrial Pollution Control of Chongqing Education Commission (CXQT19023), the project of Chongqing Technology and Business University (1853061), and Science and Technology Research Project of Chongqing Municipal Education Commission (KJZD-M202000801).  
Not applicable.  
The authors acknowledge all partners of the CTBU, IES-Arish University, BUC, HBRC, UAB, and ERU for support. The authors also acknowledge [PERSON], the National Research Base of Intelligent Manufacturing Service, Chongqing Technology and Business University, for her contribution throughout the research work.  
The authors declare no conflict of interest.