Analysis of contaminants and their formation mechanism in the desiccation-dissociation process of organic impurity of waste glass.

The recovery of waste glass is an important issue in the fields of social sustainable development and resource recovery. The removal of organic impurity is the first step in the recovery of waste glass. Currently, desiccation-dissociation technology is advised to remove the organic impurity from waste glass. However, the risks of the organic impurity desiccation-dissociation process of waste glass have not been reported in the literature. In this paper, the environmental risks of the organic impurity desiccation-dissociation process of waste glass were assessed. The assessment results indicated that none of TSP (0.143 mg/m3), PM10 (0.090 mg/m3), heavy metals in air and residue after desiccation-dissociation were contaminated. However, the gas contained abundant organic contaminants, especially benzene, whose content was up to 5.26%. Molecular dynamics simulation and contaminant formation pathways analysis indicated that the formation of gaseous organic contaminants was because overmuch small molecular free radicals were generated at 200 °C and combined with each other. Hence, reducing the temperature of desiccation-dissociation, wearing gas masks, and placing organic gas contaminant absorption liquids are necessary protective measures. This paper provides scientific data for the green development of organic impurity desiccation-dissociation technology of waste glass. Meanwhile, this paper makes up for the shortage of the environmental information of the organic impurity desiccation-dissociation of waste glass.

A novel approach of accurately rationing adsorbent for capturing pollutants via chemistry calculation: Rationing the mass of CaCO3 to capture Br-containing substances in the pyrolysis of nonmetallic particles of waste printed circuit boards.

Pyrolysis technology is advised to dispose nonmetallic particles of waste printed circuit boards to produce oils and gases. During pyrolysis, brominated flame retardants in nonmetallic particles are converted into small-molecular Br-containing substances. They disperse into oil and gas so as to cause secondary pollution. Then, CaCO3 is suggested to be employed to capture the small-molecular Br-containing substances. However, too much CaCO3 will produce over solid wastes. Less CaCO3 might not capture the total Br-containing substances. How to ration the mass of adsorbent for capturing pollutant has not been detailed investigated. This paper found HBr was the main Br-containing substances during high temperature pyrolysis of nonmetallic particles. The capture process of HBr was detailed investigated by the method of computational chemistry. At the condition of 973 K and 100 Pa, HBr was captured by chemical reaction and physical absorption of CaCO3. Unit cell of CaCO3 reacted with two HBr to form CaBr2, and the generated unit cell of CaBr2 can adsorb 0.011 HBr. 0.0106 g CaCO3 can absorb all HBr produced by high temperature vacuum pyrolysis of 1 g nonmetallic particles. This paper contributes a novel approach to accurately ration the mass of adsorbents employed for capturing pollutants.