Study On Adsorption Capacity Of Modified Biochar For Cd In Water

Biochar is a solid carbon-rich material obtained by pyrolysis(generally below 700“C)under anaerobic or anoxic conditions using biomass as the main raw material.The utilization of biochar can not only enrich soil carbon sinks and nutrients.Structure,enhance soil porosity,and can promote good adsorption of heavy metal pollution,effectively reducing the bioavailability of heavy metals.With the deepening of research,the adsorption of heavy metal Cd by biochar prepared by ordinary methods can not be matched with its developed pore structure.and the temperature of biochar preparation has an important influence on the structure and properties of biochar.Therefore,this paper mainly studies the physicochemical properties,adsorption characteristics and practical application of conventional biochar prepared by conventional biochar and rice stalk(3?scm)under different temperature gradients(300?600?).The comparison of the adsorption effects in the following results:(1)Comparing the physicochemical properties of general biochar and modified biochar prepared at different temperatures,cation exchange capacity and elemental composition,it was found that the yield of two types of biochar increased with the increase of pyrolysis temperature.The content of functional groups showed a downward trencl,the porosity of biochar increased continuously.the degree of aromatization and stabilization of biochar increased,and the structure of biochar changed from "carbon skeleton" which was gradually and obviously changed to "crushed" and "collapsed";(2)Through the study on the adsorption properties of general biochar and modified biochar prepared by different temperature gradients,it was found that the modified biochar(M-300)prepared at 300? was heavy metal Cd under the condition of a certain amount of addition.The best removal effect is obtained.The adsorption of heavy metal Cd by different biochar additions shows that the biochar prepared at low texnperature has good adsorption capacity.When the same removal rate is reached,the addition amount of M-300 is only half of general biochar;(3)The adsorption characteristics of biochar at different adsorption temperatures have been found.With the increase of external temperature(15?45?).the adsorption rate of biochar on heavy metal Cd increases,and the adsorption process ot biochar on heavy metal Cd can it is well expressed by the Lagerence quasi-secondary adsorption kinetics equation.The calculated qe(mod)is not much different from the actual adsorption amount qe(exp).It can be further inferred that the ion and exchange processes of biochar and Cd are mainly chemical.Adsorption is dominant;(4)It can be seen from the results of isothermal adsorption experiments of two types of biochar that the adsorption process ot Cd by two types of biochar can be well described by Langmuir equation,and the adsorption of biochar prepared at low temperature is better,300?.The specific adsorption amount of common biochar produced at 45? to Cd reached 17.80 mg/g,and the specific adsorption capacity of modified biochar prepared at 300? to Cd reached 22.93 mg/g at 45?;(5)The results of the adsorption process of two types of biochar on Cd-contaminated hydroponic lettuce showed that the enrichment factor of Cd was significantly decreased in the roots and leaves of lettuce after adding biochar,and the presence of lower concentration of Cd could stimulate The growth and development of lettuce,in which modified biochar prepared at 300?,had the best removal effect on Cd.In summary,the adsorption effect of M-300 prepared by the FeC13 modification method at 300? is the best.