Analysis of copper and calcium–fulvic acid complexation and competition effects

摘要: Abstract The binding of Cu2+ and Ca2+ to a fulvic acid (FA), simulating naturally occurring conditions, was studied. Furthermore, copper–FA complexation in the presence absence calcium compared. For this, potentiometric titrations were carried out using solution FA at concentration 100 mg L−1, ionic strength 0.1 M. Ca2+–FA reaction pH 6.5, 7.5 8.5 Cu2+–FA 5.5 both ion. ion had significant effect on copper [Ca2+]⩾2.5×10−3 M. experimental curves analyzed non-electrostatic discrete site continuous distribution models. Competition by mainly affected maximum capacity complexation, whereas slight observed constant appears indicate that only competes for specific sites, thus modifying sites function. It also found number occupied represented 20% total groups ionized values