Property And Mechanism Studies Of The Activated Caobon(Fiber) Adsorption And Regeneration Toward Cr Under Electrochemical Conducts

In this study, activated carbon granule (AGG) and activated carbon fiber felt (ACFF) were used to study the mechanism and influence factors of the Cr adsorption in the wastewaters under different electrochemical environment. Voltage polarity, voltage size, ionic strength and initial pH were considered as the main influence factors. Both Cr(VI) and total Cr concentration in the solution were determined. In order to study the mechanism of the adsorption, SEM and XPS methods were usd to analysis the AGG/ACFF properties before and after adsorption. Electrochemical regeneration was also conducted in order to form an integration technology of electrochemical adsorption and regeneration.When the electric field applied to the system was rounded and uneven, the influence of the acticated carbon granule adsorption was remarkable. Both adsorption rate and capacity increased under electrochemical conducts. The adsorption improved with the inciease of the voltage within limits, but if the concentration of the aqueous solution was too high, the effects of the electric field reduced. If the elecrric field was inverted after adsorption, the sdsorption and desorption would conducted simultaneously, but adsorption outstripped desorption generally.When the electric field applied to the system was even, positive voltage can improve the avtivated carbon fiber felt (ACFF) adsorption of Cr. Both electric field and ionic strength of the solution were important influence factors of the ACFF adsorption. Moreover, the adsorption performed best under acid conditions. Results showed that, the best electrochemical adsorption condition was:1g/L NaCl,5V of voltage. The adsorption process contained four typical steps without electric field existed:the external surface adsorption, the intraparticle diffusion stage, the reaction with electron and the final equilibrium stage. After reaction, Cr(Ⅵ) was reduced to Cr(Ⅲ), which was adsorbed by ACFF or partly released into the solution. However, when the electric field existed, chrome-contained ions moved faster toward the electrode covered with ACFF under the application of electric field, thus the speed of the surface adsorption in the first step accelerated. Moreover, the existence of other ions (such as Cl-) and electric field enhanced the reaction with electron of Cr(Ⅵ), leading to larger percentage of the reduction from toxic Cr(Ⅵ) to Cr(Ⅲ) on the adsorbent surface, thus improved the adsorption capacity and speed of ACFF. Electrochemical regeneration ratio can be above100%under suitable condition (1g/L NaCl,5V of voltage). The electrochemical adsorption and regeneration technology can be integrated together, and a kind of new efficient, energy saving and environmental friendly water treatment process is formed.