REMOVAL OF LEAD WITH ORANGE PEEL (CITRUS SINENSIS) IN AQUEOUS SOLUTIONS

The presence of heavy metals such as Hg, Cd and Pb in water is an environmental problem because of its high toxicity. Therefore, national and international normatively restrictive limits imposed as to their concentrations in all water types. The European Community (EC) under Directive 2008/105/EC provides for all cases lower values 10 μg L^-1 while Mexican Norm allows ranges from 0.5 to 0.2 mg L^-1 depending of water use. The adsorption of waste materials with some functional chemical groups is an effective technique to remove metals. The orange peel (Citrus sinensis) containing cellulose polymers and pectin with electronegative hydroxyl (OH-) groups is capable of interacting with metal species. The objective was to evaluate the removal efficiency of Pb⁺² soluble in solutions with concentrations above 0.2 ppm using orange peel demethylated. Demethoxylation process consisted of washes with deionized water at 60°C and 96% alcohol and subsequently treated with 0.2M NaOH to pH 10, dried and milled. Solutions at pH 3 and concentration ranges near 0.3 and 0.8 ppm were stirred at times 1, 3 and 6 h with 0.5 g of previously shell demethylated. The remaining soluble Pb⁺² of each solution were measured by atomic absorption at 283 nm and the absorbance values were correlated with corresponding levels of Pb⁺² in calibration curves. Removal percentages were estimated by difference of initial and final concentration. Maximum values (85.82% ± 3.975) were reached at 0.375 ppm. At higher levels, there was a downward trend. Similar behavior was observed to correlate concentration and stirring times. Low percentages of removal (24.96±4.869) were found to 0.757 ppm and 6 h while 0.375 ppm maximum values were achieved with increasing trends. The analysis of data showed a double interaction (P≤0.01).It is recommended to carry out more studies to elucidate possibly interactions among treatments, concentrations, agitation times and effects of temperature, pH and amount of biomass.