Kinetics of Cd^2＋ and Cr^3＋ Sorption from Aqueous Solutions Using Mercaptoacetic Acid Modified and Unmodified Oil Palm Fruit Fibre（Elaeis guineensis） Adsorbents

In this paper, we mainly study the relation of two cyclically reduced words w and w ′on the condi- tion they have the same trace polynomial (i.e., tr w= trw ′). By defining an equivalence relation through such operators on words as inverse, cyclically left shift, and mirror, it is straightforward to get that w ~ w ′ implies tr w = tr w ′. We show by a counter example that tr w = tr w ′ does not imply w ~ w ′. And in two special cases, we prove that tr w = tr w ′ if and only if w ~ w ′.

Kinetics of Cd2+ and Cr3+ Sorption from Aqueous Solutions Using Mercaptoacetic Acid Modified and Unmodified Oil Palm Fruit Fibre(Elaeis guineensis) Adsorbents

The kinetics of the sorption of Cd2 and Cr3 from aqueous solutions by mercaptoacetic acid modified and unmodified oil palm fruit fibre adsorbents were investigated. The results indicate that sorption equilibrium was reached within 60 min for both metals. Also, the removal efficiency of the three adsorbents was observed to increase for both metals with stronger treatments with mercaptoacetic acid. This may be attributed to the influence of the thiolation of the adsorbents. Furthermore, Cr3 had higher removal percentages than Cd2 for all the adsorbents. The sorption mechanism based on the intraparticle diffusion model shows that Cd2 sorption is better described than Cr3 . The intraparticle diffusion rate constants, K1d, for Cd2 are 62.04 min-1 (untreated), 67.01 min-1 (treated with 0.5 mol/L mercaptoacetic acid), and 71.43 min-1(treated with 1.0 mol/L mercaptocacetic acid) while those for Cr3 are 63.41 min-1 (untreated), 65.79 min-1(0.5 mol/L acid treated), and 66.25 min-1 (1.0 mol/L acid treated).