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 neutralizati...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展开更多
The cost of raw materials has the largest contribution to the final price of biodiesel produced by traditional routes, currently adopted in most industrial scale processes. That contribution comes from the need to use...The cost of raw materials has the largest contribution to the final price of biodiesel produced by traditional routes, currently adopted in most industrial scale processes. That contribution comes from the need to use edible and noble oils, with low acidity, such as soybean oil. This work proposes＇the use of Macauba oil, a vegetable oil in focus in the State of Minas Gerais, Brazil, in which the current extractive yield generates a raw material with high acidity, therefore, not suitable to be used in biodiesel production. To make it technically feasible, a cationic exchange resin, the Purolite CT275DR, was used as a catalyst for esterification reaction with samples of Macauba oil, aiming to reduce its acidity. The resin can be reused, regenerated and easily removed from the reaction product, reducing costs with catalyst and purification stages. As a result of this work, in a sample of oil with an initial acidity of about 10% m/m were achieved acidity reductions up to 97% by using cationic resins as catalyst, demonstrating its potential use in the oil pretreatrnent step. Additionally, the data collected during all the analysis made it possible to define the chemical kinetic of the esterification reaction.展开更多
文摘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
文摘The cost of raw materials has the largest contribution to the final price of biodiesel produced by traditional routes, currently adopted in most industrial scale processes. That contribution comes from the need to use edible and noble oils, with low acidity, such as soybean oil. This work proposes＇the use of Macauba oil, a vegetable oil in focus in the State of Minas Gerais, Brazil, in which the current extractive yield generates a raw material with high acidity, therefore, not suitable to be used in biodiesel production. To make it technically feasible, a cationic exchange resin, the Purolite CT275DR, was used as a catalyst for esterification reaction with samples of Macauba oil, aiming to reduce its acidity. The resin can be reused, regenerated and easily removed from the reaction product, reducing costs with catalyst and purification stages. As a result of this work, in a sample of oil with an initial acidity of about 10% m/m were achieved acidity reductions up to 97% by using cationic resins as catalyst, demonstrating its potential use in the oil pretreatrnent step. Additionally, the data collected during all the analysis made it possible to define the chemical kinetic of the esterification reaction.
