Modeling of titration experiments by a reactive transport model

Acid mine drainage（AMD） is commonly treated by neutralization with alkaline substances.This treatment is supported by titration experiments that illustrate the buffering mechanisms and estimate the base neutralization capacity（BNC） of the AMD.Detailed explanation of titration curves requires modeling with a hydro-chemical model.In this study the titration curves of water samples from the drainage of the As Pontes mine and the corresponding dumps have been investigated and six buffers are selerted by analyzing those curves.Titration curves have been simulated by a reactive transport model to discover the detailed buffering mechanisms.These simulations show seven regions involving different buffering mechanism.The BNC is primarily from buffers of dissolved Fe,Al and hydrogen sulfate.The BNC can be approximated by：BNC = 3（C_（Fe） ＋ C_（Al）） ＋ 0.05C_（sulfate）,where the units are mol/L.The BNC of the sample from the mine is 9.25×10^（-3） mol/L and that of the dumps sample is 1.28×10^（-2） mol/L

Antacid effects of Chinese herbal prescriptions assessed by a modified artificial stomach model

AIM:To assess the antacid effects of the tonic Chinese herbal prescriptions,Si-Jun-Zi-Tang(SJZT) and Shen-Ling-Bai-Zhu-San(SLBZS).METHODS:Decoctions of the tonic Chinese herbal prescriptions,SJZT and SLBZS,were prepared according to Chinese original documents.The pH of the prescription decoctions and their neutralizing effects on artif icial gastric acids were determined and compared with water and the active controls,sodium bicarbonate and colloidal aluminum phosphate.A modified model of Vatier's artificial stomach was used to determine the duration of consistent neutralization effect on artificial gastric acids.The neutralization capacity in vitro was determined with the titration method of Fordtran's model.RESULTS:The results showed that both SJZT and SLBZS have antacid effects in vitro.Compared with the water group,SJZT and SLBZS were found to possess signif icant gastric acid neutralizing effects.The duration for consistent neutralization of SLBZS was signif icantly longer than that of water.Also,SLBZS and SJZT exhibited signif icant antacid capacities compared to water.CONCLUSION:SJZT and SLBZS were consistently active in the artificial stomach model and are suggested to have antacid effects similar to the active control drugs.