Numerical simulation of chemical reaction – solute transport coupling model of 2,4-DCP in groundwater

• Published in: Desalination and water treatment 2020-04, Vol.183, p.346-354
• Main Authors: Zhang, Yongxiang, Huang, Xuezheng, Gao, Weichun, Wang, Youhao, Chang, Shan
• Format: Article
• Language: English
• Subjects: Coarse sand; Coupling model; Groundwater; Simulation; Zero-valent iron
• ISSN: 1944-3986; 1944-3986
• DOI: 10.5004/dwt.2020.25190

A permeable reactive barrier (PRB) remediation test trough with coarse sand-supported zero-valent iron (ZVI) composite filler was designed and built. Considering the convection-dispersion and chemical reaction of 2,4-dichlorophenol (2,4-DCP) in groundwater, a coupled model of chemical reaction and solute transport of 2,4-DCP was built. The adsorption kinetics data of 2,4-DCP were fitted, the results showed the pseudo-second-order kinetic model could better describe 2,4-DCP adsorption process than the pseudo-first-order kinetic model. The model parameters were determined by static adsorption test and continuous flow dynamic tracer test. Compared with the linear model and the Langmuir model, the Freundlich model fits better with the adsorption test data, it shows that the adsorption of 2,4-DCP by coarse sand and coarse sand-supported ZVI filler was more in line with the Freundlich model. A Freundlich model showed a satisfactory fit to the equilibrium adsorption data with a correlation coefficient R2 = 0.968 for coarse sand and R2 = 0.954 for coarse sand-supported ZVI. The adsorption coefficient KF of 2,4-DCP on coarse sand and coarse sand-supported ZVI are 4.456 × 10–6 and 0.00846 respectively, the dispersion coefficient is 0.345 cm2/min, the porosity is 0.38, the specific yield is 0.1, the permeability coefficient is 4.15 × 10–2 cm/s, and the seepage velocity is 1.245 × 10–4 cm/s. The FEMWATER software and the TOUGHREACT software are used to calculate the coupling model to simulate the migration and transformation process of 2,4-DCP in groundwater. The results show that the calculated values by software TOUGHREACT do not agree well with the measured values for the failure zone of composite filler, the values calculated by software FEMWATER has better fitting effect with the measured values.