Ammonia nitrogen removal and recovery from acetylene purification wastewater by air stripping

Ammonia nitrogen (NH₄-N) contaminated wastewater has posed a great threat to the safety of water resources. In this study, air stripping was employed to remove and recover NH₄-N from acetylene purification wastewater (APW) in a polyvinylchloride manufacturing plant. Investigated parameters were initial APW pH, air flow rate, APW temperature and stripping time. The NH₄-N removal by air stripping has been modeled and the overall volumetric mass transfer coefficient (K_La) of the stripping process has been calculated from the model equation obtained. In addition, the ability of H₂SO₄ solution to absorb the NH₃ stripped was also investigated. The results indicated that under the experimental conditions, the APW temperature and its initial pH had significant effects on the NH₄-N removal efficiency and the K_La, while the effects of other factors were relatively minor. The removal efficiency and residual concentration of NH₄-N were about 91% and 12 mg/L, respectively, at the optimal operating conditions of initial APW pH of 12.0, air flow rate of 0.500 m³/(h·L), APW temperature of 60 °C and stripping time of 120 min. One volume of H₂SO₄ solution (0.2 mol/L) could absorb about 93% of the NH₃ stripped from 54 volumes of the APW.