Study On Removal Of Pb²⁺、Cd²⁺、Cr⁶⁺ In Water By Ulothrix

With the rapid development of industrialization,Water heavy metal pollution is getting more and more serious.The algae biosorption technology is Environment friendly which attracts the scholars’ s attention in recent years. This paper selected Ulothrix as study objects,which collected from a ditch in the high-tech zone in Chengdu city. Firstly,Single factor experiments was used to research the effect of time,p H,dosage and initial concentration to the removal efficiency by alive Ulothrix. Secondly, Single factor experiments was used to research the effect of time,p H,dosage,initial concentration and temprture to the removal efficiency by non-alive Ulothrix(alive Ulothrix dried at 100℃),besides, Ulothrix’s selection to Pb2+,Cd2+. was studied.The adsorption kinetics and adsorption isotherm of non-alive Ulothrix were studied.The influence degree of factors were researched though orthogonal experiment. the main conclusions were as follows:(1) The paper showed that the removal of Pb2+,Cd2+and Cr6+by alive Ulothrix involved two steps: rapid surface adsorption and slow active absorption. The adsorption of Pb2+,Cd2+and Cr6+by non-alive Ulothrix was rapid,and equilibrium was established in two hours.(2) The influence of p H on alive Ulothrix’s removal efficiency of Pb2+,Cd2+was similar to non-alive Ulothrix’s. In a certain p H range,the removal efficiency of Pb2+,Cd2+increased with the increase of p H value;When the p H exceeded the certain range, the removal rate would decrease. There was an optimum p H range. Cr6+removal efficiency decreased with increase of the p H value.(3) The temperature almost didn’t affect the removal efficiency of Pb2+、Cr6+ by non-alive Ulothrix the removal efficiency of Cd2+affected a little by temperature,which the removal efficiency increased by 5% with the 20 degree’s increases.(4) Ulothrix’s adsorption to heavy metals was selective. When Pb2+、Cd2+ coexist, the adsorption capacity of Pb2+was more than Cd2+.(5)There were three steps for adsorption of Pb2+、Cd2+、Cr6+by non-alive Ulothrix,which were rapid adsorption,slow adsorption, equilibrium.The adsorption equilibrium of Pb2+、Cd2+、 Cr6+were established in 120,120,60 minutes respectively. It was found that the pseudo-second order equation provided the best correlation to the data. The correlation coefficients were over 0.99.(6) The adsorption of Pb2+、Cd2+、Cr6+by non-alive Ulothrix accorded with Langmuir adsorption isotherm.The high correlation coefficients of Langmuir adsorption isotherm indicated that the adsorption by non--alive Ulothrix was Single molecule adsorption. At 25 ℃, the maximum adsorption capacity of Pb2+、Cd2+、Cr6+ were 125mg/g,14.7mg/g,11.9mg/g under fitting for Langmuir adsorption isotherm. Ulothrix was one of the promising adsorbents for heavy metal wastewater treatment.Using a large freshwater green algae--- Ulothrix removing heavy metals in water was the innovation of this paper. It aimed to find a new kinds of biological adsorbents, which was efficient and cheap.