Fe-modified Clinoptilolite is Effective to Recover Plant Biosurfactants Used for Removing Arsenic From Soil

The aim of this study was to determine the effect of the biosurfactant concentration, pH, and extraction time on arsenic (As) removal from brownfield soils by saponin (SAP), and tannic acid (TA). Sandy loam (soil 1) and silt loam (soil 2) soils containing 7598.4 and 4294.2 mg As/kg, respectively, were tested. After washing, the effluents were treated with clinoptilolite modified with FeCl3 and then their ability to remove As was compared with the control biosurfactant solutions. Removal of As increased gradually as SAP and TA concentration increased (0.005-5%). Arsenic was more efficiently removed under acidic (pH 2-3) than alkaline conditions (pH 9-11). The distribution of As in soils affected the length of extraction time. A pseudo-second-order kinetic model gave a good fit for kinetic data for both biosurfactants. The efficiency of As removal depended on the soil and biosurfactant type. Under optimized conditions (3% SAP and TA, pH 3, 24 h extraction), As removal from soil 1 and 2 was 27 and 46% with SAP and 5 and 39% with TA, respectively. Modified clinoptilolite at a dosage of 300 g/L removed >= 80% of As from SAP and TA effluents. Although the reused biosurfactants did not extract As as effectively as the original solutions, pH adjustment improved their effectiveness.