Study On Phytoremediation Of Phenol In Water By Two Aquatic Plants

With the rapid development of chemical industry worldwide (including oil, chemical engineering, pesticide, printing, paper making, medicine, monosodium glutamate, dye, fuel and coal coking), a large amount of phenol compounds are used widely as raw materials. Excessive discharge of phenol wastewater and utilization of phenol pesticide are beyond the self-purification ability of environment, which have caused serious pollution. The industrial effluent, especially the phenolic wastewater, have produced various toxic effects on living matters including humans. So it is becoming increasingly important to treat the phenol compounds in water effectively.So far, technologies for treating phenol compounds consist of chemical, physic-chemical and biological technologies. Using aquatic plants in water restoration is a branch of biological technologies. It is popular due to features of new-type, economical, effective, having no second pollution and non-breaking. Especially some plants are environmental adaptability, distributed widely and easy to cultivate and collect, which are considered as excellent water-cleaning materials. Thus they have great potential to treat the industrial waste water and domestic sewage.Two widely distributed aquatic plants, Polygonum orientale Linn, and Typha orientalis Presl, have great exploiting value, including edible, economical, medical, ecological and tourism values. However, abundant resources of Polygonum orientale and Typha orientalis in Shanxi province are ignored in the past. Inefficient use of resources caused great waste. Furthermore, large amount of dry and dead plant body pile up on the river sides, which making the watercourse blocked.Based on the above reasons, Polygonum orientale and Typha orientalis were selected as experimental materials, which were ground in powder, and investigated their cleaning ability on phenol in the water. Effects on adsorption action of adsorption time, usage amount of adsorption agent, ion concentration and solution pH were studied concretely. The kinetic and thermodynamic models were established to analyze adsorption process and mechanism. In order to verify results and reuse the resources, desorption experiments were conducted on saturate adsorption of Polygonum orientate and Typha orientalis. The results showed as follows:(1) The adsorption equilibrium time of dry Polygonum orientale and Typha orientalis was 120 and 135 minutes respectively, while the optimal adsorbent dosage was 20 and 14.3 g/L respectively.(2) The effects of temperature were obvious and the adsorption both increased with increasing temperature. The effects of solution pH were also obvious. The adsorption results of dry Polygonum orientale increased with increasing pH, but decreased when in over alkaline environment. But solution pH showed contrary effect on dry Typha orientalis.(3) Based on pseudo-first-order, pseudo-second-order and kernel interior diffusion models, the kinetic features of adsorption process to phenol were analyzed and discussed. The results showed that adsorption process of dry Polygonum orientale and Typha orientalis could be described accurately by pseudo-second-order kinetic model. Kernel interior diffusion process was not the only control step.(4) Langmuir and Freundlich models were used to analyze the thermodynamic characters. Results showed that Langmuir model could well represent thermodynamic adsorption characters of dry Polygonum orientale on phenol in the solution; phenol was adsorbed by dry Polygonum orientale automatically and this process was endothermic. Results showed that Freundlich model coul well describe thermodynamic adsorption characters of dry Typha orientalis on phenol in the solution; phenol was not adsorbed by dry Typha orientalis automatically and this process was not endothermic.(5) Desorption experiments were conducted on saturate adsorption of Polygonum orientale and Typha orientalis using sterilized water, NaOH and ethanol. Results reflected that the two plants showed good analytical effects when using ethanol as desorption agent; dry Typha orientalis showed good desorption effects when using sterilized water and NaOH as desorption agent, with dry Polygonum orientale the opposite was the case. The two plants had potential to be reused.In a word, both dry Polygonum orientale and Typha orientalis showed good adsorption effects on phenol. They were able to treat phenol in water, and had higher application values and prospects.