Abstract
The agricultural crops are recognized as inexpensive and abundant biomaterials. Their use for the biosorption of pollutants has attracted great concern. Herein, powdered pergularia tomentosa fruit, a locally available biomaterial, was characterized and used for the biosorption of methylene blue in batch mode. FT–IR spectroscopy revealed that the hydroxyls (–OH) were the main groups responsible for the biosorption of methylene blue. SEM depicted a rough and heterogeneous surface with the presence of some cavities. The thermal decompositions of pergularia fruit were observed at 233 °C and 393 °C which were ascribed to the decomposition of cellulose and non-cellulose constituents, and to the depolymerization process. The effect of the operational conditions such as pH, time, dye concentration, adsorbent dose, temperature, and ionic strength on the biosorption performance was carried out. Several classical and statistical models were used to fit the experimental data. The monolayer model with two energies was the most appropriate. This statistical model revealed that two functional groups of the pergularia tomentosa fruit surface contributed to the adsorption of methylene blue. Each group is characterized by a particular energy and a stoichiometric number. The pergularia tomentosa fruit could be anchored by one or more dye molecules per site. The adsorption energy is lesser than 20 kJ/mol. The results confirmed a physio-sorption process. The maximum biosorption was 152 mg/g. The ionic strength disfavored the biosorption system. The results demonstrated that pergularia tomentosa fruit is an attractive candidate for removing cationic dyes from contaminated water.