Characterisation of dairy processing sludge using energy dispersive X-ray fluorescence spectroscopy

The dairy processing industry generates significant volumes of dairy sludge and recycling onto land could provide a source of nutrients for crop production. This work assessed the feasibility of energy dispersive X-ray fluorescence spectroscopy (XRF) for the direct, elemental analysis for land application. XRF intensities were calibrated using fundamental parameters (FP), matching libraries (ML) and empirical (EMP) standards. For major nutrients phosphorus (P), potassium (K), magnesium (Mg), sulphur (S) and aluminium (Al) each calibration method provided an excellent fit to conventional analysis. Agreement statistics computed the Concordance Correlation Coefficient (CCC) that expresses agreement in which a value of 1 represents perfect agreement and a value of 0 represents no agreement. The CCC values for FP calibrations fell between 0.8820 and 0.9925 representing excellent agreement with ICP values, and outperformed other calibration methods in XRF. Copper (Cu), manganese (Mn), zinc (Zn) and nickel (Ni) recorded R-2 between 0.8037 and 0.9868, for FP and ML calibrated values with empirical calibrations showing moderate agreement (R-2 0.6510 to 0.8855). Trace elements fell within narrow limits of agreement with negligible bias with CCC values between 0.8335 to 0.9930. XRF can provide rapid and accurate analysis of dairy sludge without the need for empirical standards. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.