Preparation of chemically treated rambutan (Nepheuum lappaceum L.) peel for the removal of basic and reactive dyes from aqueous solution / Rasyidah Alrozi, Norashikin Ahmad Zamanhuri and Mohamed Syazwan Osman

Commercially available adsorbents are still considered expensive due to the use of non-renewable and relatively expensive starting material such as bituminous coal. Therefore, this study investigates the potential use of tropical fruit waste such as rambutan peel (RP) that available in Malaysia, as the precursor for the preparation of chemically treated adsorbent which can be applied for the removal of two types of dyes, which are basic Methylene Blue (MB) and reactive Remazol Brilliant Blue R (RBBR) from aqueous solution. Impregnation with hydrochloric acid (HCI) and sodium hydroxide (NaOH) was used in order to modify the surface characteristics of the prepared adsorbent. In this study, adsorption of MB and RBBR dye by NaOH-treated rambutan peels (N-RP) and HCI-treated rambutan peels (H-RP) were examined. The adsorption experiments were carried out under different conditions of initial concentration (25-500 mg/L), solution pH 2-12 and adsorbent dose (0.05-1.0 g). The influence of these parameters on the adsorption capacity was studied using the batch process. MB and RBBR adsorption uptake were found to increase with increase in initial concentration and contact time. The MB adsorption was unfavourable at pH<4 whereas RBBR adsorption was favaourable at pH>4. Langmuir, Freundlich and Temkin isotherm models were used to illustrate the experimental isotherms and isotherms constant. The equilibrium data were best represented by Langmuir isothem model, showing maximum monolayer adsorption capacity of 231.34 and 112.69 mg/g for MB and RBBR dye, respectively. The rates of adsorption were found to obey the rules of pseudo-second order model with good correlation for both dyes. The result suggested that the N-RP and H-RP would be an excellent alternative for the removal of MB and RBBR dye by adsorption process.