Biosorption Study of Zn(Ii), Cu(Ii), Pb(Ii) And Cd(Ii) Ions by Palm Leaves Activated Carbon

The aim of the present study is to investigate the efficiency of palm leaves activated carbon on the removal of lead (Pb), zinc (Zn), copper (Cu), and cadmium (Cd) from the aqueous solution. The effect of various process parameters such as pH (2 – 10), initial metal ion concentration (50 – 1000 mg/L), particle size (125, 500, 800 μm), and temperature (303, 313, 323 K) was studied using batch adsorption technique. Thermodynamic parameters were also evaluated. The maximum metal ion removal efficiency of 94.5, 94.1, 87.4, and 90.7% for Pb, Cd, Zn, and Cu, respectively, was reached at an optimum pH of 5, biosorbent dosage of 1.0 g, and initial metal ion concentration of 50 ppm. The Freundlich adsorption isotherm model best described the removal of metal ions on palm leaves activated carbon with high correlation coefficients (0.98 – 1.00). The adsorption process was found to be favorable since the intensity of adsorption, n lies within 1 to 10. The adsorption capacity values were 40.0, 38.3, 38.0, and 40.00 mg/g for lead (Pb), zinc (Zn), copper (Cu), and cadmium (Cd), respectively. The metal ion adsorption was also found to be endothermic in nature. The efficiency was increased with an increase in temperature implying the process should be performed at a controlled temperatur

The Alkaline Hydrolysis of Sulfonate Esters: Challenges in Interpreting Experimental and Theoretical Data

Sulfonate ester hydrolysis has been the subject of recent debate, with experimental evidence interpreted in terms of both stepwise and concerted mechanisms. In particular, a recent study of the alkaline hydrolysis of a series of benzene arylsulfonates (Babtie et al., Org. Biomol. Chem. 10, 2012, 8095) presented a nonlinear Brønsted plot, which was explained in terms of a change from a stepwise mechanism involving a pentavalent intermediate for poorer leaving groups to a fully concerted mechanism for good leaving groups and supported by a theoretical study. In the present work, we have performed a detailed computational study of the hydrolysis of these compounds and find no computational evidence for a thermodynamically stable intermediate for any of these compounds. Additionally, we have extended the experimental data to include pyridine-3-yl benzene sulfonate and its N-oxide and N-methylpyridinium derivatives. Inclusion of these compounds converts the Brønsted plot to a moderately scattered but linear correlation and gives a very good Hammett correlation. These data suggest a concerted pathway for this reaction that proceeds via an early transition state with little bond cleavage to the leaving group, highlighting the care that needs to be taken with the interpretation of experimental and especially theoretical data