High Value Recycling Of Paper-Plastic-Aluminum Composite Packaging Materials

The extensive use of paper-plastic-aluminum composite packaging products brings many conveniences to people’s life,but its special composite structure leads to difficult recycling with high energy consumption and high cost.Therefore,the low recycling rate leads to a large environmental load and waste of resources.At present,although many technical methods are used to recycle paper plastic aluminum composite packaging products,there are some disadvantages,such as low separation efficiency and high impurity content of recycled products.In this study,the wastes of Tetra Pak,which has a large output among paper-plastic-aluminum composite packaging products,are takes as the research object With high-value recycling as the research purpose,the precise quality separation of paper/plastic/aluminum and the value-added regeneration of aluminum-plastic wastes are realized.The main contents are as follows:1.The influences of Tetra Pak mass fraction in water,stirring time,temperature,stirring rate and other factors on the separation rate of paper fibers and the length distribution of recycled paper fibers in the process of hydraulic pulping were investigated.On this basis,active medium was added to the pulping system to increase the swelling rate of paper fibers,accelerate the stripping speed of paper base,and improve the separation rate of paper fiber.The results show that when the mass fraction of Tetra Pak in wateris 8%,the stirring time is 30 min,the stirring rate is 500 r·min^-1,and the temperature is 35 ^oC,the separation rate of paper fibers is only 50.87%.After adding three different active media to the system,the paper fibers separation rate increased,among which the surfactant sodium dodecyl benzene sulfonate（SDBS）had the greatest influence.When the concentration of SDBS was 0.6%,the separation rate of paper fibers could reach 96.58%.The active medium can accelerate the swelling rate of paper fibers and improve the separation rate of paper fibers,so as to reduce the energy consumption of hydraulic pulping process.And the present of surfactant can guarantee the amount of high-quality long fibers to a greater extent.2.The aluminum-plastic film is accurately separated by the method of lye infiltration-mechanical separation to obtain recycled low density polyethylene（LDPE）film with low impurity content and strong alkaline aluminum-containing waste liquid.The combination of the strong alkaline aluminum-containing waste liquid and polymeric aluminum chloride（PAC）can be used as a flocculant to treat paper-plastic separation wastewater.While completing the aluminum-plastic separation,it realizes"Treating the wastes with wastes".The experimental results show that when the liquid-solid ratio is 100:1,the concentration of Na OH is 4 mol·L^-1,the soaking time is 240 min,the stirring rate is 500 r·min^-1,and the soaking temperature is 40 ^oC,the aluminum leaching rate is 94.55%,and there is no obvious aluminum spot found on LDPE film.In addition,the results also proved that the aluminum-plastic separation waste liquid has a certain flocculation ability,and its flocculation ability can be enhanced by compounding with PAC.3.Self-suspension photocatalytic devices based on the aluminum-plastic substrate are prepared by the combination of solid-state shear milling（S³M）technology,3D printing technology and surface thermal deposition technology to realize the value-added regeneration of waste aluminum-plastic.The experimental results show that when the concentration of Ti O₂ suspension is 2 g·L^-1 and the deposition temperature is 50 ^oC,the degradation rate for tetracycline hydrochloride（TC·HCl）(30 mg·L^-1)of AP-Ti O₂-50 self-suspension photocatalytic device is 93.64%under 4 h simulated sunlight radiation,which is higher than that of powder Ti O₂ with the same loading（85.30%）.And the self-suspension photocatalytic device shows good cycling stability.This method can be extended to the preperation of self-suspension devices with different photocatalysts.All of AP-Zn O,AP-Cd S,AP-g-C₃N₄,and AP-Pt-Ti O₂ self-suspension photocatalytic devices show better photocatalytic activity than the powder photocatalysts with the equal loadings.The aluminum-plastic substrate self-suspension photocatalytic device has excellent activity and cycle stability because it can be suspended on the water surface which greatly improvs the utilization of sunlight and is able to timely supplement of oxygen consumption during the process of photocatalytic,the metal aluminum contained in the substrate can accelerate the separation of photogenerated electrons and holes,and the photocatalyst can be firmly supported on the aluminum-plastic substrate.