Abstract
In this work, an original mathematical model for metals leaching from electronic waste in a dark fermentation process is proposed. The kinetic model consists of a system of non-linear ordinary differential equations, accounting for the main biological, chemical, and physical processes occurring in the fermentation of soluble biodegradable substrates and in the dissolution process of metals. Ad-hoc experimental activities were carried out for model calibration purposes, and all experimental data were derived from specific lab-scale tests. The calibration was achieved by varying kinetic and stoichiometric parameters to match the simulation results to experimental data. Cumulative hydrogen production, glucose, organic acids, and leached metal concentrations were obtained from analytical procedures and used for the calibration. The results confirmed the high accuracy of the model in describing biohydrogen production, organic acids accumulation, and metals leaching during the biological degradation process. Thus, the mathematical model represents a useful and reliable tool for the design of strategies for valuable metals recovery from waste or mineral materials. Moreover, further numerical simulations were carried out to analyze the interactions between the fermentation and the leaching processes and to maximize the efficiency of metals recovery due to the fermentation by-products.
Highlights
In this work, an original mathematical model for metals leaching from electronic waste in a dark fermentation process is proposed
The integration of the leaching with the dark fermentation (DF) process represents a promising strategy for metal recovery as: (i) organic acids produced in the fermentative process avoid the utilization of chemicals; (ii) no external energy supply is required for metals recovery; (iii) PF or anaerobic digestion (AD) can be adopted for the leachate downstream treatment with the production of a renewable energy source; (iv) the use of organic waste to feed the DF stage leads to biomass valorization in the biorefinery context; (v) any additional gaseous compounds can be trapped avoiding toxic emissions
Increasing temperature usually leads to microorganism selection and enhancement of hydrogen production rates, while a neutral pH is usually recommended for DF processes devoted to H2 generation
Summary
An original mathematical model for metals leaching from electronic waste in a dark fermentation process is proposed. The integration of the leaching with the DF process represents a promising strategy for metal recovery as: (i) organic acids produced in the fermentative process avoid the utilization of chemicals; (ii) no external energy supply is required for metals recovery; (iii) PF or AD can be adopted for the leachate downstream treatment with the production of a renewable energy source (hydrogen or methane); (iv) the use of organic waste to feed the DF stage leads to biomass valorization in the biorefinery context; (v) any additional gaseous compounds can be trapped avoiding toxic emissions. The integration of the DF with the leaching process still requires high research efforts, mainly due to the uncertainty and the limited knowledge on inhibition/stimulation dynamics generated by metals in DF reactors In this framework, mathematical modeling represents a useful tool for investigating innovative and still poorly known processes[22]; it allows for testing a wide range of environmental conditions avoiding experimental tests, and for designing the correct management of any-scale applications. These tools are able to calculate the equilibrium composition of a diluted aqueous system, and they are generally applied to determine metal concentrations in lab-scale experiments or natural ecosystems
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
