No abstract

A new biosorbent, sulfuric acid (H2SO4) treated spent grated coconut (Cocus nucifera) (SSGC) showed a good ability to remove methylene blue (MB) from aqueous solutions. Equilibrium time was achieved within 300 min for all MB concentrations, and the kinetic data was best modeled by pseudo second-order. The adsorption data fitted the Langmuir isotherm model, suggesting monolayer coverage of MB over a homogeneous adsorbent surface. The experimental maximum adsorption capacity was 366.50 mg/g, obtained at 318 K, adsorbent dosage of 0.6 g/L and at pH 6. The attachment of MB on SSGC was confirmed by Fourier Transform Infrared (FTIR) spectroscopy.

No abstract

A batch system investigated the application of two types of chemically modified biosorbents derived from spent grated coconut (Cocos nucifera) powder to adsorb methylene blue (MB) from aqueous solutions. The biosorbents were characterised by spectroscopic and quantitative analyses. The assessment of MB adsorption onto the investigated biosorbents was studied at different experimental conditions with different pHs (2-9) and different initial concentrations of MB (10-400 mg/L) at three different temperatures (298, 308, and 318 K). The maximum adsorption capacity (q max ) of xanthated spent grated coconut (XSGC) was higher than that of hexane-washed spent grated coconut (HSGC). The thermodynamic study indicated that the MB adsorption process was spontaneous for both biosorbents. Desorption of MB-loaded biosorbents was carried out using HCl, NaOH, and Na 2 EDTA solutions. A desorption ratio of more than 90% was obtained over three adsorption/desorption cycles for HSGC. However, XSGC demonstrated poor MB desorption, implying a stronger MB interaction with XSGC, which could be attributed to H-bonding, Yoshida H-bonding, n-π, and π-π bonding. The study showed that HSGC and XSGC could be applied as biosorbents to remove low MB concentrations from aqueous solutions.

The effect of physicochemical parameters on methylene blue (MB) adsorption by sulfuric acid treated spent grated coconut (SSGC) was investigated. The field emission scanning electron microscope (FESEM) images showed a change in surface morphology of spent grated coconut before and after acid treatment. Energy dispersive X-ray (EDX) spectrometer suggested the mechanism of ion-exchange occurred during MB adsorption onto SSGC. The pHpzc value of SSGC was 5.40. The amount of MB adsorbed remained constant after pH 3. The optimum dosage of SSGC was observed at 0.03 g, while the stirring rate did not significantly affect the amount of MB adsorbed. This work suggested electrostatic attraction and ion-exchange as the main mechanisms involved in MB adsorption.