The present study investigates the electrocoagulation-electro-oxidation (EC-EO) process for the treatment of restaurant wastewater (RWW) loaded with organic and inorganic matter, oil, grease, and suspensions solids. The EC-EO process was evaluated in terms of its capability to simultaneously produce an oxidant and coagulant agents by using either iron or aluminum electrodes arranged in a bipolar configuration or graphite electrodes arranged in a monopolar configuration in the same electrolytic cell. Relatively high concentrations of active chlorine (9.6 mg/min) and aluminum (20–40 mg Al/L) or iron (40–60 mg Fe/L) were produced in situ. The best performance for RWW treatment was obtained by using aluminum and graphite plates alternated in the electrode pack and operated at current of 0.4 A during 90 min of treatment with pH adjusted to approximately 7.0. Under these conditions, more than 98% of oil and greases (O&G) were removed, whereas chemical oxygen demand (COD) and biological oxygen demand ...

An innovative, efficient, and economically viable process for the recycling of spent alkaline batteries is presented herein. The developed process allows for the selective recovery of Zn and Mn metals present in alkaline batteries. The hydrometallurgical process consists of a physical pre-treatment step for separating out the metal powder containing Zn and Mn, followed by a chemical treatment step for the recovery of these metals. Sulfuric acid was used for the first leaching process to dissolve Zn(II) and Mn(II) into the leachate. After purification, Mn was recovered in the form of MnO₂, and Zn in its metal form. Furthermore, during the second sulfuric acid leaching, Na₂S₂O₅ was added for the conversion of Mn(IV) to Mn(II) (soluble in the leachate), allowing Mn to be recovered as MnCO₃. Masses of 162 kg of Zn metal and 215 kg of Mn (both in the form of MnO₂ and MnCO₃) were recovered from one ton of spent alkaline batteries. The direct operating costs (chemicals, labor operation, utilities, energy) and indirect costs (amortization, interest payment) required for a plant treating 8 tons of spent batteries per day was calculated to be $CAD 726 and $CAD 534 per ton, respectively, while the total revenue from the sale of the metals was calculated at $CAD 1359.6 per ton of spent batteries. The development of this type of cost-effective industrial process is necessary for a circular economy, as it contributes to addressing environment- and energy-related issues, and creates opportunities for the economic utilization of metals.