Effect of pH on the performance of olive pips reactive barrier through the migration of copper-contaminated groundwater

Adsorption data are modeled using the popular Langmuir and Freundlich isotherm models. These isotherms are primarily useful for simulating data collected at a fixed pH value. This study attempted to develop an adsorption isotherm based on the Langmuir model, to simulate pH-dependent adsorption effects. It is derived based on the results of a batch of experiments conducted under appropriate conditions using olive pips as the reactive bio-sorbent on a copper-contaminated solution. This isotherm is used as a linear correlation between the maximum adsorption capacity and the initial pH values of the feed solution, while a nonlinear power correlation is used to represent the affinity coefficient-initial pH relationship. This isotherm is integrated with the advection-dispersion equation for simulating the effect of the initial pH on the contaminant transport scenarios. The integrated model, solved numerically by the implicit finite difference method, is proven, in which the initial pH has a potential effect on the retardation factor and longevity of the bed of olive pips. This bed can be used as a permeable reactive barrier in the remediation of contaminated groundwater. A good concurrence between the integrated model predictions and experimental results for breakthrough curves was recognized with the index of agreement (d), as proposed by Willmott, not less than 0.999.