Transport Behavior of Cu2+ Under Binary and Multi-Component Systems in the Columns of Polyaluminium Chloride and Anionic Polyacrylamide Water Treatment Residuals: Implication for Reuse in Stormwater Bioretention Systems [Erratum: August 2022, v.233(8); p.348]
2022
Duan, Runbin | Chen, Jing
The lack of information from column studies of Cu²⁺ transport in polyaluminium chloride and anionic polyacrylamide water treatment residuals (PAC-APAM WTRs) has been hampering their reuse as a media in stormwater bioretention systems. The transport behavior of inactive tracer Br⁻ and Cu²⁺ in various systems with and without the presence of Pb²⁺, Cd²⁺, and Zn²⁺ was investigated in the columns of PAC-APAM WTRs under saturated steady flow conditions. Modeling Br⁻ breakthrough curves (BTCs) using CXTFIT revealed that the transport of a solute in the columns was an equilibrium process almost without stagnant water, with all active sites on PAC-APAM WTRs being instantaneously available for the adsorption reaction during transport (βₚ = 0.99 and ωL = 100). The results of modeling Cu²⁺ BTCs with HYDRUS-1D showed that the chemical non-equilibrium two-site model (R² 0.8911–0.9999; RMSE 0.00–0.05) described the experimental data of Cu²⁺ better than the equilibrium convection–dispersion model using the linear isotherm (R² 0.4877–0.9901; RMSE 0.02–0.12) and the Langmuir isotherm (R² 0.7083–0.9938; RMSE 0.01–0.10). The fraction of instantaneous adsorption sites at the equilibrium (fₑ) of Cu²⁺ decreased with the increase of co-existing heavy metal ions from 0.27 (monocomponent system) to 0.06 (quaternary system) due to competitive adsorption with the Cu²⁺, Cd²⁺, and Zn²⁺ systems as an exception. The first kinetic rate (ω) of Cu²⁺ increased with the increase of competitive heavy metal ions from 0.0076 (monocomponent system) to 0.0410 (quaternary system). This research could contribute to the understanding of Cu²⁺ transport and potential leaching in stormwater bioretention systems.
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