Copper recovery from printed circuit boards leaching solution with bioelectricity generation using microbial fuel cell.

Recovery of valuable metals via leaching printed circuit boards (PCBs) has gained moment recently. This work studied the Microbial fuel cell (MFC) performances for recovery of Cu from a Cu2+ solution by examining key operating parameters. A dual-chamber MFC with 6 cm × 6 cm × 7 cm dimensions was constructed. Both anode and cathode electrodes were made of a carbon cloth sheet. The anodic and cathodic chambers were separated by a Nafion membrane. The highest Cu recovery efficiency was 99.7% after 240 h batch mode operation, yielding 102 mW/m2 MFC power density output using 1 g/L Cu2+ solution as the catholyte (initial pH 3) and an anolyte containing 1 g/L sodium acetate inoculated with a sludge from a wastewater treatment plant's anaerobic pond, with 2 cm distance between the electrodes made of polyacrylonitrile polymer. The highest open circuit voltage, current density (based on cross-section cathode area) and power density with an external load of 1 kΩ was 555 mV, 347 mA/m2 and 193 mW/m2, respectively. Additionally, recovery of Cu in the leachate of PCBs using sulfuric acid leaching after 48 h was performed and the highest Cu recovery was 50% in 48 h.

Permeability and percolation of anisotropic three-dimensional fracture networks.

The percolation properties and permeability of a group of anisotropic three-dimensional fracture networks are studied numerically. Finite-size scaling is used to extrapolate the percolation thresholds of infinite networks in three spatial directions, i.e., X , Y , and Z directions. The influence of the angular dispersion parameter of fracture orientations on percolation thresholds is analyzed. In this analysis, we considered a family of fractures in a three-dimensional space that are oriented around the Z axis based on the Fisher distribution. We revealed that increased anisotropy leads to decreased percolation thresholds in both X and Y directions, and in these two directions percolation thresholds in anisotropic networks demonstrate a declining trend as anisotropy goes up. However, in the Z direction the trend is the opposite. The fracture networks are triangulated via an advancing front technique and the macroscopic permeability of the networks is determined by solving the two-dimensional Darcy equation in each fracture. We found that the macroscopic permeability in the X and Y directions is higher than the associated permeability of isotropic fracture networks, and this property for anisotropic networks in the Z direction is lower compared with that of the isotropic case. Furthermore, as the anisotropy of networks increases the differences become more remarkable.