- Thesis topic: Application of atmospheric microwave plasma on vitrification of resin from the PCB Waste

- Doi: https://doi.org/10.6840/cycu202100220

- Abstract: 

      Plasma technology has been used widely for the environmental applications and environmental clean-up, especially to eliminate the harmful elements and vitrify the materials via the ionization from plasma discharged, Recently, however, the using of plasma technology, which consume a lot of energy, is an expensive technology as well as the flux agent to vitrify the material. Therefore, the finding of the cost-less flux agents for vitrification and inertization of pollutants, calculation of technology based on the economic perspectives, development of strategies, selection of proper technology for the reusing the material from plasma post-treatment for fulfill the concept of circular economy are necessary to be performed.
       In this dissertation, cost-less flux agents, namely, shells powder from Babylonia formosae and Haliothis diversicolor, and bone powder from pork and chicken bone waste, obtained from food wastes were prepared, characterized, performed and compared with the commercial flux agents on the removal of harmful elements using an atmospheric pressure microwave plasma reactor to deal with resin from printed circuit board (PCB) waste (e-waste). Moreover, the quantitative and qualitative studies of environmental evaluation and environmental economic were formulated to develop the strategies to apply this material in the real application as a cost-less flux agent based on the SWOT analysis. To obtain proper parameters in an atmospheric-pressure microwave plasma reactor: pyrolysis duration, microwave power, gas flow rate, gas types and flux agent ratio were assessed via a Taguchi Method. Also, the special focus on the parameters, such as crucible distance and addition of quartz sands, were assessed. Lastly, the elimination elements from hyper-accumulator plants (Water hyacinth and Water lettuce) and its potential as an activated carbon was conducted, and the residue from plasma post-treatment, chicken bone waste, and pork bone waste were tested in the adsorption and photocatalyst application.
        The fuse of shell powder shows an efficiency removal of benzene and toluene at value 98.8% and 100 %, respectively. Then, the higher ratio of shell powder improves inertization of metals and metalloids more than 96%. Calcite formation (CaCO3) can be found in the final residue, confirming the degradation of metals and metalloids. The addition of higher ratio of flux agents (Babylonia formosae, Haliothis diversicolor, quartz sand and limestone) compared to samples (1:2) shows a good vitrification, and it is supported by the closer position of crucible to the plasma jet discharged. Based on the economic perspectives, flux agents from food waste may tackle the cost issues in plasma technology. Also, there are 12 strategies that may be formulated derived from SWOT analysis based on the external and internal condition in the development of cost-less flux agent. Then, Taguchi methods confirmed that nitrogen gas with 9 L/min of gas flow rate, the fuse of 1 g quartz sand from the sample, pyrolysis in 10 minutes and 1200 watt of microwave power with the lowest concentration of Zn was 0.21 mg/L (99.72%). The most important factor for plasma pyrolysis was 10 minutes of duration, which indicated the greater result compared to other parameters.
The treatments of Water hyacinth and Water lettuce indicate a good removal of elements (As, Cd, Cu, Cr, Co, Ni, Pb, and Zn) with the value less than 1.4 mg/L. Activated carbon derived from water hyacinth from plasma post-treatment indicated the maximum capacity with the value at 175.57 mg/g, and the adsorption occurs at the monolayer condition in the acid blue. In the experiment of activated carbon derived from chicken bone waste and from plasma post-treatment were 139.41 mg/g and 142.23 mg/g, respectively. For the photocatalyst test, TiO2 doped with chicken bone waste and pork bone removes 81% and 63.3% of NOx, under the solar light irradiation. Lastly, the atmospheric-pressure microwave plasma reactor combined with the pork bone indicates good results to decrease the concentration of As and Pb from PCB were 37.30% and 2.58%., respectively. Furthermore, 700 mg/L of Cu from PCB and 4720 mg/L of Zn from resin can be recovered using the leaching with 8 mol/L H2SO4, and chicken bone/pork bone combined with quartz sand and glass/cullet indicates a proper vitrification of resin and PCB.
       To summarize, the addition of cost-less flux agents shows a promising result on the vitrification, inertization of elements and recovery of precious elements in an atmospheric-pressure microwave plasma reactor, and potentially may be applied in the environmental applications ith the proper strategies. In addition, the material from plasma-post treatment with the presence of flux agents from shell powder and bone wastes may be reused to the in the adsorption and photocatalyst application, and fulfill the concept of circular economy.

Keywords: Adsorption, photocatalyst, circular economy, flux agents, inertization, microwave plasma reactor, resin, vitrification