沸石去除污水處理廠放流水中磷酸鹽之效能評估

Abstract

本研究旨在利用天然沸石為吸附材料，吸附放流水中的磷酸鹽。研究中以中部某科學園區污水處理廠含磷酸鹽之放流水及人工合成磷酸鹽溶液為標的，進行等溫吸附和吸附動力實驗，來探討各操作條件下，天然沸石對磷酸鹽之吸附量與吸附平衡時間的影響；並評估天然沸石去除污水處理廠放流水中磷酸鹽之效能。

研究結果顯示，天然沸石對於磷酸鹽去除效率之最佳pH值為9，而利用Langmuir等溫吸附模式模擬各實驗條件的數據結果，顯示Langmuir吸附模式可用於描述天然沸石吸附水中磷酸鹽之行為。吸附動力實驗結果顯示，當反應溫度、pH值、吸附劑及吸附質條件相同下，吸附時間為1小時，其結果為吸附反應速率快、達到吸附平衡時間短，因此證明天然沸石對磷酸鹽之吸附行為，在極短的時間內達到飽和。其反應速率與操作因子的關係，符合擬二階動力模式。

本研究應用天然沸石去除中部某科學園區污水處理廠放流水中之磷酸鹽，研究結果顯示去除磷酸鹽的機制有二：其一反應溶液初始pH值為9的條件下，對於磷酸鹽的去除是有利的，由吸附實驗反應溶液pH值的變化可以推論，天然沸石表面官能基置換水中磷酸鹽的機制為吸附反應，其二為天然沸石在pH為9的鹼性條件下交換性的Ca2+、OH-和PO43- (HPO42-中的形式)可能會發生沉澱作用而被去除。

In this research, we used natural zeolites as adsorbents to adsorb phosphates in the effluent, and we chose the effluent from the sewage treatment plants of some Central-Taiwan Science Park and synthetic phosphate solution as our research targets to study the adsorption behavior of phosphates.the effects of natural zeolite on the adsorption capacity of phosphate and the equilibrium time of adsorption were investigated.the effects of natural zeolite on the removel of phosphate in effluent from wastewater treatment plant werw evaluated. Research results showed that the optimum pH value of natural zeolite for phosphate removal efficiency is 9,and the Langmuil adsorption model can be used to describe the adsorption of phosphate in natural zeolite by Langmuir isothermal adsorption model.research results of adsorption experiments show that when the reaction temperature,pH value,adsorbent and adsorbate conditions are the same the adsorption time shortened to about one hour; and the result was faster adsorption rate and shortened adsorption equilibrium time. therefore, it proved the adsorption behavior of phosphates by natural zeolites could reach saturation in a very short period of time, and reaction rate and operating factors were in accordance with quasi-second-order dynamic model.

In this research, we used natural zeolites to remove phosphates in the effluent from the wastewater treatment plants of some Central-Taiwan Science Park. There were two phosphate removal mechanisms we found from the research results. One of them was that it’s beneficial to remove phosphates when the initial pH value of the reaction solution was 9. And this can be inferred from the changes of its pH values that the mechanism of natural zeolites’surface functional groups replacing phosphates in the effluent was an adsorption reaction. The other mechanism was that , under the alkaline condition (pH 9), the exchangeable Ca2+, OH-, and PO3-4 could be precipitated by natural zeolites and got rid of.