Eletrodissolução de alumínio em polpa celulósica proveniente da reciclagem de embalagens cartonadas multicamadas

Abstract

In this work we studied the aluminum electro-dissolution in cellulose pulp from milk and beverage cartons recycling. The objective for this research is to reduce the aluminum particles sizes to values below 300 μm. In the first stage, the process was studied in lab scale using an electrochemical reactor anode made of Titanium recovered with ruthenium oxide (DSA® Ti/Ti0.6Ru0.3O2- De Nora do Brasil) and cathode made of titanium without recovering. In this experiment in lab scale, the electro-dissolution of aluminum presented a first order kinetic reaching 88 to 92% of electrochemical efficiency after 500 minutes. From measurements of particles diameter by optical microscopy it was possible to calculate the total area occupied by the aluminum particles which was quantified by image efficiency. For the lab experiment the image efficiency reached values between 74 and 88%. This first study was conducted in three current density: 250, 320 and 700 A/m2 and during 60, 180, 480 and 960 minutes. After 60 minutes no particles above 300 μm was detected. In the second stage, a pilot electrochemical reactor was designed taking the lab reactor parameters and keeping the same material for anode and cathode. This system was evaluated for current densities of 22, 250 and 270 A/m2 during 120 and 420 minutes. The best result was observed with the application of 250 A/m2 during 420 minutes reaching electrochemical and image efficiency of 60 and 72% respectively. The mechanical resistance for the cellulose pulp was evaluated before and after the electrochemical treatment and it was noted that it affected the freeness in a positive way. Tear, tensile, burst, zero span tensile index and stretch, if compared to non-treated and refined pulp to the same freeness, presented effects positive or negative depending on the current density applied and the treatment time. However, all the measurements for mechanical properties after the electrochemical treatment are in the acceptable level for paper market. The energy consumption was evaluated for the lab and pilot experiment and optimized industrial conditions were simulated. Based on these simulations and on the experiments results, we can conclude that a plant that recycles 50 ton per day of milk and beverage cartons needs 655 kW of electric power to treat all the pulp extracted from these packages using the electrochemical process considering that paper represents 75% (w/w) of milk and beverage cartons composition.