Simulate permeable reactive barrier by using a COMSOL model and comparison with the Thomas, Yoon–Nelson and Clark models for CR dye remediation by composite adsorbent (sewage and waterworks sludge)

The remediation of Congo Red (CR) dye by the synthetic sorbent composited from sewage and waterworks sludge was studied in batch and continuous experiments. The continuous experiments studied the composite synthetic after mixing with composite synthetic sorbent filter (CSF) glass waste to increase the hydraulic conductivity of the permeable reactive barrier (PRB). The synthetic composite sorbent was characterised by the nitrogen adsorption–desorption tests, field emission-scanning electron microscopy and X-ray diffraction. For evaluating the batch tests, the variable conditions of initial concentration, solution pH, agitation time and agitation speed were studied. The synthetic sorbent showed a high ability to remove the CR from a contaminated water, with maximum sorbent uptake equal to 9,469.211 mg/g and composite adsorbent-filter CSF equal to 4,415.946 mg/g. Pseudo-second-order kinetic model and Langmuir isotherm model governed the adsorption process. The column tests showed the highest reactivity, with 50:50 weight ratios of the adsorbent to filter glass waste. The experiments were done with different concentrations of CR and different bed heights of CSF as the PRB for 90 days. There was a delay in the breakthrough time when decreasing the contaminant concentrations and when increasing the composite adsorbent-filter CSF bed height. The breakthrough curves were well represented by the COMSOL model.