Electrophoretic Studies of Turbidity Removal by Coagulation With Aluminum Sulfate

Abstract

One important factor affecting coagulation is the negative zeta potential, often referred to as the charge, that is associated with natural clay particles suspended in water. This article discusses a study of the zeta potential of clay particles that were found to be dependent on the pH and on the alum dosage. An amount of alum equivalent to several times the base‐exchange capacity of the clay suspension was required to neutralize the particle charge. Clarification was best in the range pH 7.5 – 8.5 where the particles were negative, rather than at pH values where the particle charge had been neutralized. Fair coagulation was often obtained below pH 4.5 where the particles were nearly neutral. In many instances, residual turbidities changed sharply without any accompanying change in mobility values. The eight coagulant aids used with alum all could be made to improve or inhibit coagulation by selection of dosages of alum and aid. As in the coagulation at different pH values, final particle charges could not be correlated with residual turbidities.

Kinetic study on the sedimentation behavior of Na- and Ca-kaolinite suspension in the presence of polyethyleneimine

“…According to the method of Schofield and Samson (1954) these fine particles (2 lm) were treated with 0.5 M NaCl or CaCl 2 solution to convert the kaolinite to the sodium form (Na-or Ca-kaolinite). The cation exchange capacity (CEC) of Na-kaolinite was determined by using ammonium acetate (1 M) as described by Black and Hannah (1961). The cation content was determined by atomic absorption spectrophotometer, Shimadzu Corporation, AA-6701/6601 Series.…”

Effect of Sulfate and Other Ions in Coagulation With Aluminum(iii)

“…Mattson 8 in 1928 reported on his extensive electrophoresis studies of clays and concluded that the hydrolysis products of aluminum and iron are primarily responsible for the neutralization and coagulation of electronegative colloids. He further stated that these hydrolyzed species are more effective than the three-plus ion itself.…”

“…As described by Peterson and Bartow, 1 and again by Black, Rice, and Bartow," sulfate has the effect of broadening the pH range of coagulation to the acid side. In a previous study, the present authors 8 investigated the coagulation of the Gram negative bacterium Escherichia coli by aluminum nitrate. Changes in turbidity during settling were used as an indication of aggregation and the entire aluminum nitrate concentration-pH "domain of stability" for the coagulation of the organisms was established.…”

Filetrability Techniques for Improving Water Clarification

“…Although electrophoretic mobility was recognized by Reuss in 1809, it was not related to water or water treatment before 1928, when Mattson published his ground-breaking study.' Even then, it was not until Black [2][3][4][5][6] and associates published a series of papers beginning in 1958 that ZP in water treatment received the attention it deserved.…”