Simulation Of Copper And Zinc Ion Adsorption Process And Spectral Induced Polarization Monitoring

In recent years,heavy metal pollution has become an extremely severe problem due to the increasing frequency of human activities such as industrialization,urbanization,and energy consumption,resulting in the release of large amounts of heavy metals such as lead,copper,and cadmium that pose significant harm to the environment and human health.These heavy metals are difficult to degrade and migrate in the environment,accumulate in organisms,and further transmit through the food chain,causing chronic and acute toxic reactions and even diseases such as cancer.Permeable Reactive Barrier(PRB)technology is a widely used in-situ groundwater treatment method for remediation of heavy metal pollutants in groundwater and one of the most commonly used methods in site remediation.Therefore,exploring barrier materials in PRB for repairing heavy metal pollution has important engineering significance.The effective adsorption and removal of heavy metals is essential for the remediation of heavy metal pollution,and the achievement of successful removal is closely related to the characterization and study of heavy metal adsorption processes.Traditional pollutant transport detection methods,such as groundwater observation wells,soil drilling,sampling,etc.,are time-consuming,labor-intensive,costly,and greatly influenced by sample acquisition.Therefore,emerging geophysical methods have attracted the attention of many scholars in the study of pollutant transport characterization due to their non-invasiveness,comprehensiveness,high accuracy,and economic efficiency.Among these methods,electrical resistivity tomography(ERT)and induced polarization(IP)are currently the most widely used techniques.However,compared to these two methods,spectral induced polarization(SIP),due to its high sensitivity to the electrochemical properties of porous media surfaces,is more suitable for exploring the adsorption mechanism and microstructure of pollutants.Currently,research on using SIP technology to monitor heavy metal adsorption in barrier materials is relatively scarce.Taking into account the insufficiency of previous studies,this paper investigates the adsorption process of heavy metal ions Cu(II)and Zn(II)onto activated carbon and biochar using spectral induced polarization(SIP)technology,which provides a support basis for field applications.The main content is presented as follows:(1)The primary mechanisms for adsorption of activated carbon are ion exchange and physical adsorption,whereas biochar exhibits a more complex adsorption mechanism due to its richer functional groups,including ion exchange,surface complexation,and precipitation.The better blocking effect caused by the more diverse adsorption mechanisms can be reflected by the SIP signal response.(2)The adsorption kinetics of both activated carbon and biochar follow the pseudo-second-order kinetic model,while the Freundlich model better fits the adsorption isotherm of activated carbon.The adsorption isotherm of biochar fits the Langmuir model at low concentrations and the Freundlich model at high concentrations.The thermodynamic study of adsorption at 298,308,and 318 K indicates that all adsorption processes are spontaneous and endothermic.(3)The SIP signal response exhibits significantly different trends during the column breakthrough experiments of activated carbon and biochar,and different adsorption ion species also affect the SIP signal.This demonstrates the ability of SIP technology to differentiate between different porous media materials and different pollutants.(4)The corresponding relationship between relaxation time and primary pore size distribution was validated by fitting the SIP signal with a double Cole-Cole model.Normalized chargeability displays a linear relationship with adsorption amount and maximum adsorption capacity,indicating thatm_n can serve as an indicator for monitoring the adsorption process.Ion concentration and species affect the relaxation time and normalized chargeability.The overlapping of multiple Cole-Cole terms indicates that the polarization mechanism is not singular.