Removal of Copper Ions from Aqueous Solution by Bentonite Clay Applied in Soil in Leaching Columns

The objective of this research was to evaluate the effect of bentonite applied in soil, on the removal of copper (Cu) from aqueous solutions, in leaching columns. The experiment was carried out at laboratory using leaching columns filled with 4 kg of soil mixed with bentonite according to treatments B0, B30, B60 and B90, that is, 0; 30; 60 and 90 t ha-1 of bentonite. Each leaching column (experimental unit) was constituted of a PVC tube, with 0.10m of diameter and 0.50m height sectioned in two 0.20 m rings (10-30 cm and 30-40 cm) and one, on the top, of 0.10 m high, reserved for a hydraulic head of 0.08 m. The columns were placed in a vertical support and saturated with distilled water by capillary ascension. Then percolation began, passing through the column five volumes of pores (initially four liters of water contaminated with 1000 mg of Cu and afterwards one liter of distilled water). Ten leached aliquots of 0.5 volume of pores were collected and stored in polypropylene flasks in a refrigerator for quantification of copper (Cu) by atomic absorption spectrophotometry. At the end of the tests, the solid material contained in each ring was collected and the Cu concentration determinated. Increasing doses of bentonite increased Cu retention in soil; Cu was more retained in the surface layer in all treatments; there was no copper leaching from the columns with 60 and 90 t ha-1 of bentonite application, indicating that all copper was retained in the soil avoiding thus potential risks for groundwater contamination.