Modified Bentonite As PRB Medium Experimental Research On Removal Of Heavy Metals From Groundwater

China is the world's largest freshwater resource reserves,ranking fourth in the world,but also the world's per capita fresh water resources,one of the most scarce countries.With the rapid development of urbanization,the rapid development of industrialization and mining and smelting and other factors,the heavy pollution of groundwater pollution is becoming increasingly serious.Groundwater pollution remediation concerns the well-being of all human development,the current repair of groundwater pollution is imminent.Permeable Reactive Barrier technology is a new type of groundwater in situ repair technology,and it is also a hot research topic of groundwater pollution remediation.It has the advantages of low energy consumption,low cost and no pollution to the surface environment.Bentonite is a kind of mineral clay rich in our country,it is also an adsorbent.It has the advantages of cheap price,large adsorption capacity,good ion exchange capacity and no harm to the environment.It has a wide application prospect in water pollution remediation.Water with Cu²⁺,Cd²⁺,Pb²⁺was used as groundwater in experimental progress,which was the object of treatment,the commodity bentonite of Zhengzhou in Henan was used as the raw material,the bentonite was modified with Mg-Al,Fe-Al?1?and Fe-Al?2?three groups of polyhydroxy polymers as pillar modifiers;A series of factors influencing the adsorption effect of modified bentonite were studied;PRB simulation experiment on heavy metal pollution of groundwater with modified bentonite as PRB reaction medium was carried out to explore the feasibility and effectiveness of PRB in remediation of groundwater pollution.The results were as follow.?1?It can be seen from the orthogonal test that different modification factors on the modification of bentonite have different degrees of impact.The optimum conditions for the modification of bentonite were as follows:modifier:Mg-Al polymerization hydroxyl modifier;suspension concentration:3g/L;pillared temperature:?90±1??;aging temperature:?90±1??;Aging time:36h.The single factor test results of the respectively best group of modified bentonite in Mg-Al,Fe-Al?1?and Fe-Al?2?showed that the increase of the reaction temperature and the pH value of the solution could improve the adsorption rate of bentonite to heavy metal ions.The increase of the reaction time and the increase of the reaction time could improve the adsorption rate to a certain extent,but beyond this level,the adsorption rate remained stable.The X-ray diffraction?XRD?and scanning electron microscopy?SEM?of modified bentonite and raw bentonite were studied.The layer spacingof modified bentonite increased and the adsorption capacity increased,which improved the ability of bentonite to repair Cu²⁺,Cd²⁺and Pb²⁺in groundwater.?2?A PRB test was performed using an indoor columns which used Mg-Al modified bentonite,activated carbon,quartz sand and iron powder as the reaction media of PRB simulated columns,The feasibility and timeliness of heavy metals single pollution and complex pollution were investigated.The test results showed that it is feasible to treat contaminated groundwater uesd Mg-Al modified bentonite as reaction media of PRB;With the Bentonite-quartz sand as reaction media,the reaction column was clogged after several days of operation and the reaction was terminated;With bentonite-activated carbon-quartz sand as reaction media,decreasing the amount of bentonite or increasing the amount of activated carbon decrease the remova leffects of heavy metals;With bentonite-activated carbon-iron powder-quartz sand as reaction media,the overall removal rate of heavy metals was higher than the overall removal rate of the reaction medium as bentonite-activated carbon-quartz sand,the addition of iron powder in the medium improved the removal of heavy metals by the reaction medium.The synergistic effect of adsorption of Mg-Al modified bentonite,activated carbon and of Oxidation-reduction of zero-valent iron reduced the amount of Heavy metals in groundwater...