Application of response surface methodology for chromium removal by adsorption on low-cost biosorbent

This work focuses on the efficiency of the response surface methodology to optimize the parameters affecting the chromium removal by biosorption on orange peels. A Doehlert experimental design was applied to determine the optimum conditions. Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), Brunauer-Emmett-Teller (BET), and Boehm method were used to characterize the biosorbent. The characterization of the adsorbent revealed that the pH of zero charge is equal to 2, the specific area is about 2 m(2) g(-1). The experimental results were analyzed by the ANOVA test and showed that the model regression is acceptable. The determination coefficient R-2 was equal to 0.995 suggesting an excellent relationship between predicted and experimental responses. The highest removal yield (97%) was obtained under the following conditions: adsorbent amount of 1.12 g, a pH equal to 2 and a temperature of 34.17 degrees C. Langmuir and Temkin isotherms were found to be the best fitted models, and the maximum adsorption capacity was 7.14 mg g(-1). The adsorption process is endothermic and fits the pseudo second order model.