Classification and determination of total hardness of water using silver nanoparticles

Herein a semi-quantitative and quantitative method for rapid determination of water hardness was introduced. The method was based on color change of silver nanoparticles (AgNPs) in the presence of real water samples. Carbon dots were prepared from mulberry in a hydrothermal procedure and used as reductant of silver ion for synthesis of AgNPs. A classification method based on the color change of AgNPs in the presence of different water samples was also founded. The analysis based of the proposed method was cheap and rapid. On site semi-quantitative determination of total hardness of water can be performed by the proposed method. A linear calibration model based on the color analysis of the images of AgNPs in the presence of water samples was constructed. The model was applicable for determination of total hardness of water in the range of 116-248 mg L^-1 of calcium carbonate. A variety of real water samples were included in the calibration model. The calibration method can be used to predict total hardness of water in a critical range above the soft water and below the very hard water. The results were compared by the standard titrimetric method based on ethylenediaminetetraacetic acid. Prediction of total hardness of real water samples based on the color model was in most cases below 20%.