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Zeta Potential and Surface Area of Calcium Carbonate as Related to Phosphate Sorption
Author(s) -
Amer Fathi,
Mahmoud A. A.,
Sabet Violette
Publication year - 1985
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1985.03615995004900050013x
Subject(s) - adsorption , sorption , chemistry , zeta potential , phosphate , precipitation , pyrophosphate , reagent , nuclear chemistry , mineralogy , chromatography , biochemistry , chemical engineering , organic chemistry , nanoparticle , physics , meteorology , engineering , enzyme
Orthophosphate (OP) sorption by eight reagent‐grade CaCO 3 samples and a natural limestone, as influenced by the surface area and zeta potential (ZP), was investigated in the absence and presence of pyrophosphate (PP) as a crystal growth inhibitor. Reacting the nine CaCO 3 samples for 24 h with 1 mmol OP L −1 indicated a rapid 0.08‐h adsorption reaction and a 2‐h induction period that preceded OP precipitation. The amount of adsorbed OP was proportional to the CaCO 3 surface area which ranged from 250 to 12 780 m 2 kg −1 and accounted for 92.8% of the variation in OP adsorption. The surface area was generally proportional to the ZP, as five CaCO 3 samples were positively charged with ZP values ranging from 17.7 to 25.3 mV, three samples were noncharged, and only limestone was negatively charged with a ZP of −6 mV. The ZP decreased with OP adsorption and again increased after OP precipitation. Addition of PP did not interfere with OP adsorption, but inhibited OP precipitation during the 24‐h reaction period by extending the induction period, and markedly reduced the ZP. Negativity of the CaCO 3 particles per se was not considered the main factor in retarding P precipitation, as polyacrylamide was very effective in lowering ZP but had no effect on OP sorption. The added PP was also subject to adsorption by the CaCO 3 and, therefore, the amount of PP needed for inhibiting growth of the calcium phosphate crystals depended on CaCO 3 reactivity as well as on OP concentration.