科研之友
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摘要
Bench-scale gamma irradiation was conducted to investigate the influencing factors, such as initial cyanide concentration, absorbed dose, saturated gases, and pH value as well as water compositions on the gamma radiolysis of cyanide in simulated aqueous solution. The decomposition rate of cyanide was observed as pseudo-first-order kinetic over the applied concentrations varied from 77 mg/L to 247 mg/L. Cyanide was decomposed more rapidly at a lower initial concentration than that at a higher initial concentration. However, the radical scavengers in natural waters, such as carbonate and bicarbonate, have negative effects on the remove of cyanide. This indicated that hydroxyl radical may play predominant role in the gamma radiolysis of aqueous cyanide. Finally, ammonia and cyanate were identified as the main nitrogen-containing byproduct of gamma radiolysis of cyanide. To remove toxic hydrogen cyanide (HCN) from carbon fiber industry waste gases, a pilot-scale experiment with a self-sheltered electron beam accelerator was demonstrated after two sprays of chemical absorption. The operating conditions for absorption and irradiation had been optimized. It was shown that after the first spray tower, HCN concentration decreased from (240 50) mg/m(3) to 35 15 mg/m3. While after the second spray tower, effluent HCN was reduced almost below the method detection limit. Then, the residual cyanide in aqueous solution was exposured to high energy electron beam (EB). Influent CM-concentration was controled at (15 +/- 2) mg/L with a water regulating tank. This treatment allows CN- to reach the regional limit (of 0.5 mg/L) for safe industrial wastewater discharge with a irradiation dose of 12 kGy. The obtained results showed that the combined process were effective for removing HCN from the waste gas.
