Removal of a basic dye from aqueous solution by adsorption using Parthenium hysterophorus: An agricultural waste

Adsorbents prepared from Parthenium hysterophorus – unwanted weed – were successfully used to remove methylene blue from an aqueous solution in a batch reactor. The adsorbents included sulphuric acid treated Parthenium (SWC) and phosphoric acid treated Parthenium (PWC). Aqueous solutions of various concentrations (50–250 mg/L) were shaken with certain amount of adsorbent to determine the adsorption capacity on SWC and PWC for methylene blue. The effects of adsorbent surface change, initial pH, initial dye concentration, adsorbent dose and contact time on dye removal have been determined. Similar experiments were carried out with commercially available activated carbon (AC) for comparison. Initial pH of aqueous solution had negligible effect on the adsorption capacity of all the studied adsorbents. Maximum dye was sequestered from the solution within 60–90 min after the beginning of every experiment. At 500 mg/L methylene blue concentration, AC had 1.93 and 3.4 times more adsorption capacity than PWC and SWC, respectively. The adsorption capacity of the studied adsorbents was in the order AC > PWC > SWC. Adsorption follows both Langmuir and Freundlich isotherm models. The results showed that SWC and PWC can be considered as potential adsorbents for methylene blue removal from dilute aqueous solutions.