Research On Volcanic Materials Used For Remediation Of Copper Contamined Groundwater As The PRB Media

With the scoria and pumice of natural volcanic materials as the study object,the effects of adsorption time,dosage,solution p H and initial concentration on the removal of Cu???in groundwater from scoria and pumice were investigated in this study.The optimal modification methods and conditions of scoria were also discussed.The optimum technological conditions of Cu???from aqueous by iron-modified scoria and then the feasibility of two kinds of PRB reactivity media to remediate copper contaminated groundwater by continuous experiments were discussed.And the regeneration methods and optimum regeneration conditions of the volcanic materials were also explored.The main conclusions of this study are as follows:?1?The study parameters such as initial copper concentrations of the solution,the paiticle sizes,adsorbent/solution ratios,p H,contact times,agitation speed significantly affected the removal efficiency.The optimum conditions were obtained through the batch experiments: 20mg/L,0.15 0.425 mm,8g/L,p H=6,2h,200r/min,respectively.Additionally,the sorption data of copper were correlated well by the Langmuir isotherm and the adsorption processes fitted well with the pseudo-second-order kinetic model.?2?The result indicated that the adsorption of Cu???by pumice was more efficient than scoria,So it was necessary to carry out modification of scoria for further meeting application requirements.The results showed that removal efficiency can be improved by 2mol/L FeCl₃,which the optimum modification conditions were solid liquid ratio of 30:1 and modification time of 12 h.The optimum adsorption conditions of the iron-modified scoria were the same as those of pumice.Compared with the Freundlich model,the adsorption isotherm of Cu???fitted well with the Langmuir equation,indicating that the adsorption of Cu???by iron-modified scoria was monolayer adsorption,and the maximum adsorption capacity was 2.524mg/g.Since the pseudo-second-order kinetic model gave a good fit over the whole range of the adsorption process,the adsorption process of metal ions on the modified scoria would mainly via chemisorption process.The results indicated that the iron-modified scoria can significantly enhance the adsorption capacity due to its high specific surface area,extensively micropore structure and the increase in the amount of iron oxides on the surface of the scoria.?3?In the dynamic column tests with different flow velocity,the removal rate ofcopper under different initial concentrations for pumice PRB and iron-modified scoria PRB was above 96% and 92% at low velocity?0.3m L/min?,respectively.When the flow rate was 0.5m L/min and 1.0m L/min,the removal rate of the reaction column decreased with the treatment time.Pumice PRB and iron-modified scoria PRB had the best effect on the removal of Cu???in the initial concentration of 10mg/L,which satisfied the class III standard of "groundwater quality standard".The results showed that it was conducive to the removal of Cu???at the initial concentration of 10mg/L under present experimental conditions.?4?In the dynamic column tests in different initial Cu???concentration,the effect of pumice PRB on copper removal was better than iron-modified scoria PRB under different concentration gradient.Compared with the modified scoria PRB,pumice PRB was more suitable for the removal of Cu???in groundwater at high flow rate?1.0m L/min?.?5?Volcanic PRB has a good performance during the practical application process.After 54 days of operation,the removal rate were still about 85%,which meets the class III water quality standard of "groundwater quality standard".Therefore,pumice and iron-modified scoria could be employed as novel reaction medium for in-situ remediation of copper contaminated groundwater.?6?Regeneration efficacy with HC1 was better than high temperature activation regeneration,The optimum regeneration conditions were as follows:0.3mol/L of concentration and 60 min of regeneration duration.After five cycles of continuous adsorption/regeneration,the removal rate of Cu???by modified scoria and pumice can reach more than 80%,which shows that the two regenerated volcanic rocks still have good adsorption performance.