Determination of very low levels of gold and palladium in wastewater and soil samples by atomic absorption after preconcentration on modified MCM-48 and MCM-41 silica

A simple and rapid method was applied for extraction, preconcentration and determination of trace amounts of gold and palladium in wastewater by using functionalized mesoporous silica. Extraction was investigated on adsorbents prepared by grafting aminopropyl on the surface of MCM-41 and MCM-48 mesoporous silica. The optimum experimental conditions such as pH, flow rates, type and the smallest amount of eluent for elution of Au and Pd, break through volume and the influence of various cationic interferences on the sorption of gold(III) and palladium(II) were evaluated. The extraction efficiency for gold and palladium were greater than 98% and limit of detection (LOD) was lower than 0.06 ng mL−1 for gold and 0.1 ng mL−1 for palladium on both functionalized MCM-41 and MCM-48 silica. The preconcentration factor was greater than 800 for gold and 400 for palladium and the relative standard deviation (RSD) of the method was <1%. The adsorption capacity of the mesoporous silica was greater than 285 mg g−1 for Au and 145 mg g−1 for Pd on both functionalized MCM-41 and MCM-48 silica. The results of MCM-41 were compared with those of MCM-48 under similar experimental conditions, the results show that flow rate was the single point of difference among the procedures. MCM-48 has similar recovery to MCM-41 at higher flow rates only under identical conditions. The proposed method was applied for the determination of gold(III) and palladium(II) in some real samples, including wastewater and soil samples.