Flocculation efficiency of phosphorylated hemoglobin on kaolin and hematite systems

Abstract

Hemoglobin recovered from slaughterhouse blood has proven to be an effective flocculant of negatively charged particulate contaminants, but it is ineffective against positively charged contaminants. Phosphorylation is useful for modifying proteins to increase the number of negatively charged sites. Dry‐heat phosphorylation and chemical phosphorylation were applied to hemoglobin. The kaolin/hematite clarification efficiencies of modified hemoglobin at different dosages and pH values were determined. ζ‐potential and total phosphorus content were also measured. Chemical phosphorylation was generally more effective than dry heat phosphorylation at achieving the desired modification of properties; it produced modified hemoglobin (CPhosHb) with higher phosphorus content and lower isoelectric point, and it had greater efficiency in flocculating hematite suspensions. At the optimal dosage of 5 mg/g hematite, treatment with CPhosHb resulted in a 99% turbidity reduction in the hematite suspension after 24 h. When 500 mM calcium chloride was applied to CPhosHb, it exhibited a positive charge in the overall pH range and was capable of clarifying suspensions of negatively charged kaolin particles at low doses. From these results, the effectiveness of chemical phosphorylation on hemoglobin is demonstrated and CPhosHb can be used as a flocculant of either negatively charged or positively charged contaminants in wastewater.