Research On Photodegradation And Volatilization Of Naphthalene In Natural Waters

Naphthalene has the strongest volatility and solubility in PAHs.It is used widely in plastic industry,chemical industry,textile industry,drugs manufacture, petroleum and coal processing.Naphthalene can be detected in the wastewater of the industries mentioned above.Many water bodies such as lakes,rivers,even the under groundwater are polluted by naphthalene;it's also distributed in the harbors,soil and trash treatment plant polluted by oil.It can course changing of human blood ingredient and jaundice in long-term contact of naphthalene so it's a serious threaten to human health;naphthalene can also create toxic action to aquatic plants,it can be expressed in the way of suppressing the breath,reducing the chlorophyll content and finally lead the aquatic organism to death.Because of its high harm to human body,zoology and botany,moreover,it's a common pollutant has a high concentration in the environment that human can easily have contacts with it in this article we chose naphthalene to study its photo degradation and volatilization in nature water body.Naphthalene is a major pollutant in the Songhua River and it's also a typical sort of PAHs in the environment In this article we studied the photo degradation and volatilization in both pure water and the water of Songhua River the conclusions were listed below:Several conditions were studied to discuss the photo degradation of naphthalene such as the initial concentration,pH values,luminous intensity and the effect of NO₂^-,NO₃^-,Fe³⁺,Fe²⁺,Mn²⁺were also discussed.1.Under the conditions listed above the reaction conformed to the first-level dynamics rule. 2.Under different initial concentrations there were different naphthalene reaction rates.In the concentration range of 0.5mg/L～3.0mg/L the reaction rates of naphthalene were decreasing with the increasing of the initial concentration. In the concentration range of 0.5～1.5mg/L the reaction rate in the water of Songhua river was obviously slower than it was in pure water,when in the range of 1.5～3.0mg/L the difference became smaller.When the initial concentration of naphthalene was 2mg/L,k_p=0.1758h^-1(pure water);k_r=0.1651h^-1(river water).3.The degradation rate of naphthalene was very different under various luminous intensity.The degradation increased rapidly along with the increasing of the luminous intensity.When the luminous intensity was among 5000～21000Lux there was only slight differences between the reaction of naphthalene in pure water and river water;The difference(reaction rate was slower in the river water)became obvious under the luminous intensity of 32000Lux,when the luminous intensity was 42000Lux it reached the greatest difference.When the luminous intensity was 32000Lx,k_p=0.1758h^-1;k_r=0.1651h^-1.4.In the pH range of 2.15～11 there wasn't any difference in the degradation of naphthalene in pure water.In the river water there was also not any difference in the pH value range of 5.2～9;when pH value was 2.45 the reaction rate was promoted,k=0.1952h^-1;when the pH value was 10.95 the reaction rate was suppressed,k=0.1315.The degradation rate was promoted under strong acid condition,strong alkaline condition suppressed the rate,there wasn't any effect under slight acid or slight alkaline condition,it can be concluded pH value didn't play an important role in nature water.5.There wasn't any difference when NO₂^- existed in pure water.The degradation rate was promoted when NO₃^- existed in pure water,when the concentration of NO₃^- was 2mg/L,k=0.1921h^-1.The degradation in river water was suppressed when NO₂^- and NO₃^- existed,when the concentration of NO₂^-was 2mg/L,k=0.1330;when the concentration of NO₃^- was 2mg/L,k=0.1328.A very strong promote effect of the degradation of naphthalene could be observed when Fe³⁺and Fe²⁺were added in pure water,when the concentration of Fe³⁺ was 2mg/L,k=0.9352h^-1;when the concentration of Fe²⁺was 2mg/L, k=0.5929h^-1.There was a suppression effect when Fe³⁺was added in the river water,when the concentration of Fe³⁺was 2mg/L,k=0.1599h^-1.The reaction was strongly suppressed when Fe²⁺was added in the river water,when the concentration of Fe²⁺was 2mg/L,k=0.1147.There was a promotion of the reaction when Mn²⁺was added in pure water,but there wasn't a relationship between the promotion effect and the concentration of Mn²⁺,when the concentration of Mn²⁺was 2mg/L,k=0.1957h^-1.The reaction was suppresses when Mn²⁺was added in the river water,the suppression effect became strong along with the increasing of the Mn²⁺concentration,when the concentration of Mn²⁺was 2mg/L,k=0.1119h^-1..It could be seen under all the conditions the reaction was slower in the river water than that in pure water,except that at pH=2.45 the reaction was quicker in the river water.The trace existence of NO₂^-,NO₃^-,Fe³⁺,Fe²⁺,and Mn²⁺could also be the reason of suppression,because in the experiment they all presented suppression effects in the river water.In the study of volatilization temperature,speed of flow and wind speed was considered.6.Under the conditions mentioned above the volatilization of naphthalene conformed to the first-level dynamics rule.7.When the temperature raised of 10℃to 25℃the rate of volatilization increased three times.When the temperature was 10℃in pure water and river separately,the value of k was 0.0279h^-1and 0.0301h^-1;When the temperature was 25℃in pure water and river separately,the value of k was 0.1090h^-1and 0.1121h^-1;It could be concluded the volatilization of naphthalene is fast in summer than spring and autumn.2.The volatilization of naphthalene was quicker when there was a flow in the water.When the flowing speed was high the value of k was 0.8667h^-1and 0.7721h^-1in pure water and river water separately.It can be concluded the ability of self purify is stronger in a flowing water body than that in a lake or pond.3.The volatilization of naphthalene is promoted along with the increasing of wind speed,especially in the first 0.5h.When the wind speed was high the value of k was 0.1730h^-1and 0.1703h^-1in pure water and river water separately.