Degradation Of Persistent Organic Pollutants-Pentachlorophenol By Mechanochemical

Fore a long time, the treatment of the Persistent Organic Pollutants(POPs) is difficult in environment governance, chlorophenols aromatic compounds is one of the typical. It might cause disturbance in ecosystem and threaten human being's health because of its difficulty to be decomposed owing to the stable chemical property. Traditional methods of degradation of POPs is difficult to commercialize for they have so many disadvantages, including severe restriction on reaction condition, extortionate handing cost, complicated technological process and secondary pollution etc.We used mechanochemical method to degrade the Pentachlorophenol (PCP) that one is the typical of the POPs in this experiment. Ball and waste particles became thin and occurred continuously collision under the action of mechanical forces, consequently, the inert halogen atomic's reactivity of PCP would be boosted up, halogen atoms removed from organic carbon chains and transform to Metal halide, through the reaction between PCP and dehalogenation reagent occurred. The specific experiment process:PCP, metallic oxide and ball-grinder medium steel beads are ground together in a ball-grinder under ordinary temperature and pressure, which is a mechanochemical way of degrading PCP. A AgNO3 standard solution was used to titrate the Cl--containing solution made from grinding product. The dechlorination rate, which can show the degradation result of PCP, was calculated through the amount of AgNO3 standard solution.The results are presented as follows:1. The bigger the Metal Oxide/PCP molar ratio was, the better the dechlorination rate was:when the molar ratio is 60:1, the dechlorination rate was almost over 98%. So, the best molar ratio is 60:1 in this experiment.2. PCP dechlorination rate increased as grinding time. With increased the ball milling time, the product showed a black hue after 2.5h's grinding, which might be a sigh of formation of elemental carbon. In this experiment, the best ball milling time is 2.5h, and the radio of organochlorine transformed to inorganic chlorine was almost 2/3.3. Metal oxide species has a direct impact on the degradation of PCP. CaO is better than MgO as a grinding material for dechlorination in the same time.4. Confirmed by valence bond theory, CaO and MgO as a dehalogenation reagent can trigger the chemical degradation of PCP more easily under the action of mechanical forces.Due to its simple technological process, normal reaction condition, noticeable effect can get good treatment effect in short time, does not involved the operation of the traditional chemical unit, the mechano-chemical de-halogenations of halogenated organic has received attentions as a promising technology to destroy solid waste containing persistent organic pollutants.