Zero point charge measurements (pHpzc)
The pHpzc was determined using acid-base titration as detailed by Ahmed Adam.8 To begin, 0.5g of each AC was added to 12.5mL of DI water and heated to 90°C. Once cooled, the pH was recorded. Then, aliquots of 50 mL of 0.01M NaCl solutions were prepared in 100 mL beakers. The pH was adjusted using 0.1M NaOH and HCl from 2 to 12. Once a stable pH was reached, 0.15g of each AC sample was added to each beaker, sealed and stirred for three days. Blank tests were also made without and AC sample to eliminate CO2 impact on pH. The pHpzc was determined by analyzing a the curve of pHfinal vs. pHinitial and calculating where pHinitial=pHfinal. The pHpzc for some trials still had a very acidic pH. To ensure no H3PO4 was left, each AC was stirred in a solution of NaOH of matching or similar molarity for 24 hrs and the pHpzc trials were done again for the AC9M and AC13M.
MB absorption
The absorption on methylene blue (MB) dye was determined using the procedure by Reffas, etc..7 The absorption studies were conducted with 50 mg of activated carbon samples stirred into 50 mL of MB solutions of pH between 7 & 8 and initial concentrations of 50,100,200,400,600,and 1000 mg/L. The pH of the solutions were adjusted using 0.1M HNO3 and NaOH before AC was added. The suspensions were stirred while covered for about 27 hrs. After filtering off the AC, the solutions were centrifuged at 5000 rpm and 25°C for 10 minutes to separate any access carbon. Standard solutions of 2.5, 5, 15, 25, and 35 mg/L were created from 1000mg/L stock MB for the standard curve. The MB filtered concentrations and standard solutions concentrations were determined by spectroscopy using a Jasco V-750.
The pHpzc was determined using acid-base titration as detailed by Ahmed Adam.8 To begin, 0.5g of each AC was added to 12.5mL of DI water and heated to 90°C. Once cooled, the pH was recorded. Then, aliquots of 50 mL of 0.01M NaCl solutions were prepared in 100 mL beakers. The pH was adjusted using 0.1M NaOH and HCl from 2 to 12. Once a stable pH was reached, 0.15g of each AC sample was added to each beaker, sealed and stirred for three days. Blank tests were also made without and AC sample to eliminate CO2 impact on pH. The pHpzc was determined by analyzing a the curve of pHfinal vs. pHinitial and calculating where pHinitial=pHfinal. The pHpzc for some trials still had a very acidic pH. To ensure no H3PO4 was left, each AC was stirred in a solution of NaOH of matching or similar molarity for 24 hrs and the pHpzc trials were done again for the AC9M and AC13M.
MB absorption
The absorption on methylene blue (MB) dye was determined using the procedure by Reffas, etc..7 The absorption studies were conducted with 50 mg of activated carbon samples stirred into 50 mL of MB solutions of pH between 7 & 8 and initial concentrations of 50,100,200,400,600,and 1000 mg/L. The pH of the solutions were adjusted using 0.1M HNO3 and NaOH before AC was added. The suspensions were stirred while covered for about 27 hrs. After filtering off the AC, the solutions were centrifuged at 5000 rpm and 25°C for 10 minutes to separate any access carbon. Standard solutions of 2.5, 5, 15, 25, and 35 mg/L were created from 1000mg/L stock MB for the standard curve. The MB filtered concentrations and standard solutions concentrations were determined by spectroscopy using a Jasco V-750.