Complexations in illite–fulvic acid–Cu2+ systems

As part of an extended project to illustrate how heavy metals are complexed by natural aquatic particles, we conducted various experiments to study the adsorption of fulvic acid (FA) at aqueous illite surfaces and the complexation of heavy metal copper(II) in illite–FA bi-complexant systems. By analyzing batch adsorption and potentiometric titration data, we found that (i) the adsorption of FA by illite decreases with increases in pH values and its pH adsorption edge resembles those of SiO2–FA and montmorillonite–FA systems described by other researchers, (ii) it is possible to effectively simulate the complexation of Cu2+ ions in illite–FA bi-complexant systems by taking it to be an additive complexation of two mono-complexant systems (FA–Cu2+ and illite–Cu2+) and (iii) FA can inhibit the retention of heavy metals at solid surfaces by forming soluble complexes with metal ions. The above results and conclusions are supported by FT-IR analysis of various illite–FA–Cu2+ systems.