Effects Of Typical Adsorbent On Characteristics Of Adsorption And Leaching Of Atrazine

Atrazine has been widely used as an herbicide on pre-and post-emergent of crops and ithas been widely concerned because of its long half-life, nonbiodegradable, carcinogenicity,easy accumulated within the organism. The persistence of atrazine in soil could expandcontaminated area by leaching, runoff and even pollute the ground and surface water. Theadsorption-desorption characteristics of soil will affect the migration of atrazine. The batchexperiment and leaching experiment will verify whether the addition of biochar can improvesthe soil’s adsorption capacity and effectively reduce the effect of atrazine on environmentalhazards. And the adsorption of amended soil will be affected by pH. The reason that we chosewheat straw (WS) to produce biochar is not only because of its easy preparation method, butalso its abundant resources and the lower cost. The wheat straw was pyrolyzed under theoxygen-limited condition for1.5h at500°C, by10°C min-1. The ground biochar was sievedby20,60and100meshes. WS biochar particle size ranges are0.3-0.9mm (20-60mesh),0.15-0.30(60-100mesh),<0.15mm (>100mesh), respectively.The results of batch equilibrium showed that the adsorption capacity of soil after additionof biochar increased rapidly with the extension of time at the beginning, but it gradually reachesthe equilibrium state after2h. The adsorption equilibrium time is24h. The adsorption kineticsdemonstrated that the soil adsorption process of atrazine after the WS biochar addition followsclosely a pseudo-second-order kinetic model. The calculated qe(1.39mg g-1) agrees well withthe experimental values (qe,exp=1.37mg g-1) and the correlation coefficient values are1.00forall particles sizes. Results show that the values of RLis between0and1, and demonstrates theequilibrium data of atrazine in soil with WS biochar were well described by the Langmuir (R2=0.99) than the Freundlich (R2≤0.98) isotherm model. The identifying maximum adsorptioncapacity of biochar was less than0.15mm, Q0=5.24mg g-1, because the smaller particle sizewould own the bigger specific surface area and the mean greater contact area.The adsorption capacity of the soil would increase with the amount of WS biochar (0%,1%,2%,5%), and the optimum adsorption capacity of amended soil was blended with biochar(5%), R (removal rate of atrazine)=98.44±0.32%. When pH of the solution was neutralltycondition (pH=7), the sorption is most effective under the addition5%biochar. In simulated soil column, the concentration of atrazine (0to5cm) is about20times than blank sample in theamended soil with5%biochar. The concentrations of10-25cm soil were very low without athreat to the environment. Meanwhile, the concentration of leaching solution that derived fromamended soil column is lower than the drinking water quality standards. In conclusion, theamended soil with biochar can effectively inhibit the leaching of pesticides and increase itsbiodegradation time. The amended soil could prevent atrazine infiltrating into the groundwaterand avoid further water contamination...