Equilibrium modeling of single and binary adsorption of Cd(II) and Cu(II) onto agglomerated nano structured titanium(IV) oxide

Adsorption reactions of Cd(II) and Cu(II) with nanoparticle agglomerates of titanium(IV) oxide (NHTO) were investigated from single and bi-component systems at optimized pH 5.0. Kinetic data of metal ion removal reactions described the pseudo-second order equation very well. Both Langmuir and Redlich–Peterson models described the equilibrium data well (R2 > 0.95). Values of the monolayer adsorption capacities (mg·g− 1) of Cd(II) (49.50 to 60.24) and Cu(II) (42.02 to 52.63) were high, and that increased with increasing temperature on the reactions. Thermodynamic analyses of the equilibrium data suggested that the removal reactions were spontaneous [−∆G0, kJ·mol− 1 = 24.31 to 32.73 for Cd(II); and 19.62 to 27.38 for Cu(II)]. Spontaneity of the reactions increased with increasing temperature. Langmuir monolayer adsorption capacity of either Cd(II) or Cu(II) was less in presence of each other than that of single component systems. The mean adsorption energy estimation suggested that the interaction between either of the metal ions with NHTO was columbic type. About 71 to 75% of adsorbed metal ions could be recovered as the metal oxide from their solutions, which were obtained by the desorption reaction with 0.1 M HCl.

Research Highlights
► TiO2 is a novel, non-toxic and insoluble material with high surface active property.
► Nano-structure makes it more effective material for removing inorganic water contaminants.
► Adsorption of Cd(II) and Cu(II) from single and binary system by TiO2 showed good information.
► Adsorption capacity for the metal ions is quiet higher than many of the materials.
► Adsorbent is not leached, even in strong acid or basic medium.