Performance of zero-valent iron barrier through the migration of lead-contaminated groundwater

Abstract

The Freundlich and Langmuir isotherm models are frequently used for modeling of sorption data at constant value of pH. The present study modified the Langmuir isotherm model for simulating the sorption effects as a function of initial pH of the aqueous solutions. This model was developed using the batch results for sorption of lead from contaminated solution onto zero-valent iron (ZVI) sorbent under specified parameters. These parameters were; initial pH of (2–7), contact time (≤120 min), agitation speed of (0–250 rpm) and ZVI weight not exceeding 2 g/100 mL) for initial lead concentration ranged from 50 to 250 mg/L. Experimental results proved that the sorption capacity and affinity constants of the developed isotherm model are changed dramatically with initial pH of aqueous solution. These constants have values of 23.62 mg/g and 0.3566 L/mg at best initial pH of 5. The sorption capacity-initial pH was correlated using polynomial regression, while the affinity coefficient–initial pH was represented by linear relationship. In addition, stoichiometric ratios between cumulative iron elution and cumulative lead removal at best operation conditions proved that about 0.34 mg of iron is required to remove 1 mg of lead ions. The kinetic rate constants showed that the lead uptake was increased threefold when pH changed from 2 to 5, while this value decreased to its half when pH changed from 5 to 7.