Towards finding model pollutants for predicting CEC adsorption on biochars : The suitability of using dyes as proxies for CEC removal efficiency to enable wastewater reuse

Abstract: This study evaluated the use of common dyes as model pollutants for adsorption on biochar. Pollutant removal efficiency of five dyes and three CECs on three different biochars (SWP-550, SWP-700, NDG-SW) was evaluated, using both UV-VIS spectrophotometry and LC-MS/MS, to examine similarities and differences in adsorption performance. In a parallel study, the impact of matrix effects on the adsorption of dyes and CECs was investigated by using both ultrapure water and effluent from wastewater treatment plant (WWTP). The analytes used in the study were malachite green (MG), methylene blue (MB), crystal violet, allura red, tartrazine, trimethoprim, diclofenac (DCF), and carbamazepine (CMP). MG, MB, CMP and DCF followed the same relative pattern in removal efficiency of different biochar products. This indicates that the dyes might be useful for comparing the efficiency of removal of CMP and DCF using biochar products.However, MG and MB did not prove useful in the quantification of CMP and DCF removal efficiency. NDG-SW had the highest pollutant removal efficiency. All biochar products were efficient in removing dyes at ng/mL concentrations. The matrix effect of the effluent water was considerable, with effects resulting in both the reduction and promotion of removal efficiency. Further studies, including PCA, would be useful to map out the correlations between specific dye and CEC adsorption to biochar.