Effect of alkyl tail and oxyethylation degree on the cosorption of nonionic surfactant and nickel (II) by polyacrylic acid-functionalized cation exchanger

Mutual effect of nickel (II) and oxyethylated higher fatty alcohols CnH2n+1O(C2H4O)mH (nonionic surfactants ALM-10 at n of 12–14, m ∼ 10 and OS-20 at n ∼ 18, m ∼ 20) on kinetics and equilibrium of their cosorption, needed for designing the industrial adsorption columns, has been investigated to establish the adequacy of polyacrylic acid-functionalized cation exchanger Duolite ES-468 for the treatment of nickel plating rinse water in closed loop systems. Mutual effect depends on the length of hydrophobic chain (number of carbon atoms in alkyl tail n) and the length of hydrophilic chain (oxyethylation degree, number of –C2H4O– head groups m in the molecule of nonionic surfactant), and is affected by the solution acidity. External mass transfer of ALM-10 through the liquid film, surrounding the bead of cation exchanger, proceeds faster than that of OS-20, although is slower than that of nickel (II).Mutual interference with the external mass transfer, arising from the simultaneous film diffusion of not only nickel (II) free cations and ALM-10 free molecules but also their associates, has been observed. Although the action of nickel (II) onto the external mass transfer of OS-20, having the oxyethylation degree and mean molecular mass twice as high as those of ALM-10, was insignificant.Effective intraparticle diffusivity (Def), determined using Vermeulen model, valid for the whole range of the fractional attainment of equilibrium, is considerably higher for OS-20 than that for ALM-10. The action of nickel (II) promotes the intraparticle diffusion of ALM-10 but hinders that of OS-20. Intraparticle diffusion of nickel (II) is enhanced greatly by the action of ALM-10 and OS-20. Kinetic curves refer to the monolayer sorption, corresponding to Lagergren pseudo-first-order kinetic equation; equilibrium specific sorption (aeq) of nickel (II) and nonionic surfactants, predicted using Lagergren model, corresponds to that, determined experimentally.On increasing the solution pH from 3 to 5 the sorption of nonionic surfactant, proceeding by hydrogen bonding of oxygen in –C2H4O– head groups with hydrogen in protonated carboxyl groups decreases, whereas the sorption of nickel (II), proceeding mostly by ion exchange, increases. aeq of ALM-10, having length of alkyl tail and degree of oxyethylation twice as low as those of OS-20, is higher, and at low concentration (C < 0.5C0) breakthrough the break point occurs later than that of OS-20. The action of nickel (II) results in an increase in aeq for both ALM-10 and OS-20.Duolite ES 468 cation exchanger is applicable for recycling wastewater, containing nonionic surfactant and nickel (II), including nickel plating rinse water, preventing pollution of environment with heavy metal (II) and nonionic surfactant, and reducing water consumption.