Charge characteristics of humic and fulvic acids: Comparative analysis by colloid titration and potentiometric titration with continuous pK-distribution function model

Humic substance charge determination by titration with a flexible cationic polyelectrolyte

“…The fact that both at pH < 6 and pH > 6 an increased dissociation is observed indicates that the nature of the PAHA functional groups are not of dominant importance for the charge regulation. The better screening of the HA charges by polyDADMAC than by 1-1 salt ions is a generic electrostatic effect, and the present findings do not support the overestimation or underestimation the charge density depending on pH as found by Bratskaya et al (2008).…”

“…Weis and Frimmel (1989) were the first who used HS-polyelectrolyte interaction for HS charge determination and poly-diallyldimethylammonium chloride (polyDADMAC) was used as the strong cationic complexing agent. More recent investigations and a discussion of the method for HS have been presented by Gregory (1999, 2001) and Bratskaya et al (2008). Kam and Gregory (1999) have compared various end-point detection methods and in a second paper (2001) specific attention has been paid to HS.…”

“…Their results show: (1) that electrokinetic methods for the end-point determination are relatively simple and give good results, also for HS, and (2) for a 1-1 stoichiometry with HS cationic polyelectrolytes with a charge density larger than 3 mmol charges g À1 should be used. Bratskaya et al (2008) have compared the results of polyDADMAC titrations at different pH values with charge-pH curves obtained by proton titrations for several HS. For fulvic acids (FA) the agreement between both methods was reasonable, except for a sample that contained a high fraction with molar mass < 1.5 kDa.…”

Characterization of pH-fractionated humic acids with respect to their dissociation behaviour

“…Humic acids are composed of natural polydispersed polyelectrolyte bio-colloids occurring in water as dissolved organic matter or in sediments and soil (Bratskaya et al 2008;Davies et al 2001;Koopal et al 2001;Michalowski and Asuero 2012;Steelink 2002). A major fraction of organic matter in natural ecosystems is in fact formed by humic acids, which are characterized by the presence of several functional groups with labile protons such as carboxylic acids, phenols and amines.…”

Eletrochemical Study of the Interaction between Humic Acids Extracted from Soil and the Pb2+ Ion in Aqueous Solution

“…The main factors responsible by the lead adsorption soil capacity are the cation exchange capacity of humic acids, soil pH, soil organic matter and presence of clay minerals and CaCO 3 [4,5].…”