Calcium carbonate

All of the chemicals were of analytical reagent (AR) grade. 4-nitrophenol (99%) was obtained from Alfa Aesar (Tewksbury, MA, USA). Naphthalene (99.7%) was acquired from Mallinckrodt Pharmaceuticals (Blanchardstown, Dublin, Ireland). Potassium phosphate dibasic (98%) and potassium phosphate monobasic (99%) were purchased from Fisher Scientific (New York, NY, USA). Calcium carbonate (99%) was obtained from BDH Chemicals (Mississauga, ON, Canada). All of the stock solutions were prepared using 18 MΩ cm Millipore water (Burlington, MA, USA), unless specified otherwise. Ferric sulfate (60% w/v), lime (10% w/v) solutions, and water samples were obtained from the South Saskatchewan River water samples after primary treatment at the City of Saskatoon Water Treatment Plant (Saskatoon, SK, Canada). Aluminum sulfate (48.5% w/v) was contributed by Chemtrade Logistics (Saskatoon, SK, Canada).

2, 2-Diphenyl-1-picrylhydrazyl (DPPH), Catechin, Folin-Ciocalteu reagent and Trolox were purchased from Sigma-Aldrich Chemical Co. (St. Louis, MO, USA). Sodium phosphate, aluminium trichloride (AlCl₃) and sodium carbonate were purchased from Daejung Co. Ltd., Korea. Calcium carbonate was purchased from BDH Laboratory Supplies, England. All other chemicals were of analytical grade.