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Coconut oil mill waste (CMW) contained high free fatty acid (FFA) content which potentially could be converted into a value-added product such as fatty acid methyl ester (FAME). In this study, a montmorillonite-sulfonated carbon catalyst was used to evaluate the kinetic parameter of FFA conversion from CMW into FAME. The characterization of FTIR and SEM-EDX confirmed that the -SO3H groups were successfully incorporated into montmorillonite- carbon catalyst. The highest catalyst acidity (9.4 mmol/g) was achieved by a ratio of montmorillonite to sulfonated carbon of 1:3 % w/w. The kinetic study using montmorillonite-sulfonated carbon 1:3 % w/w showed that the reaction temperature and molar ratio of methanol to FFA (% v/v) were positively correlated to the reaction rate. The highest rate constant of esterification towards the product (k1), reactant (k2), and equilibrium were 0.1187, 0.0595, and 1.995, achieved by a temperature of 80 ˚C, respectively. The Arrhenius constant and activation energy towards the product were 3.3085×106 and 50.3 J/mole, respectively. The reaction temperature was positively correlated to the equilibrium constant, which indicated that the reaction was endothermic. The kinetic model validation revealed that the predicted value from the model was adequately in accordance with the experimental value, as indicated by a high coefficient of determination.

Bagasse is the solid waste derived from the sugar-making process. A large amount of silica in bagasse is a potential source of silica. In this study, extraction of silica from bagasse was carried out in the following steps: pretreatment of bagasse using HCl solution, followed by calcination at varying temperatures (700℃, 800℃, and 900℃) using a furnace. Furthermore, extraction using NaOH solution and precipitation using HCl. Silica characteristics were obtained using X-Ray Diffraction (XRD), Scanning Electron Microscopy-Electron Dispersive Spectrometry (SEM-EDS), and BET surface area. The results showed that calcination temperature affected the characteristics of the silica produced. The silica extracted at 700℃ produced an amorphous phase with a broad peak at an angle of 2θ = 20-24°. It contained the most considerable silica content and surface area, 42.46% and 796.89 cm2/g, respectively. The extracted silica had an average diameter of 5.67 mm and a pore volume of 1.184 cm3/g.

The composites of hydroxyapatite and SiO2 were successfully synthesized. The hydroxyapatite was prepared from golden snail shells (Pomacea canaliculata L). The hydroxyapatite and hydroxyapatite-SiO2 composites were characterized using XRD, FTIR, SEM-EDS. Furthermore, hydroxyapatite and hydroxyapatite-SiO2 composites were used to remove Pb(II) from aqueous solution. Various adsorption parameters such as pH of the solution, contact time, and initial Pb(II) concentration were used to study the adsorption process. The optimum pH of the solution for removal of Pb(II) by hydroxyapatite and hydroxyapatite-SiO2 composite at pH 6 and contact time at 60 minutes. Both adsorbents follow the Langmuir isotherm. The maximum adsorption capacity of the hydroxyapatite-SiO2 composite is greater compare to hydroxyapatite, respectively 135.14 and 123.46 mg/g. The pseudo-second order kinetic model had a correlation coefficient (R2) greater than the pseudo-first order so pseudo-second order kinetic is better to describe adsorption kinetics

In this study, MnFe2O4-activated carbon composite was synthesized by co-precipitation method and applied to adsorb methyl red dye. MnFe2O4-activated carbon composite was made with the mass ratio of activated carbon and MnFe2O4 of 1:2. The composite characterization by using X-Ray Diffraction, Fourier Transform Infrared Spectroscopy, Scanning Electron Micrograph, and Energy-Dispersive X-Ray Spectroscopy, the surface area using the Brunauer, Emmett and Teller and magnetic properties by using Vibrating Sample Magnetometer. The adsorption parameters include contact time, and adsorbent weight. The spectra of FTIR MnFe2O4-activated carbon composite analysis show the presence of Fe-O and Mn-O which is not present in the spectra of activated carbon. SEM analysis shows that the composite has pores and MnFe2O4 oxides are spread on its surface. The composition of the composite consists of C, O, Fe, and Mn. The composite has a surface area of 143.992 smaller than that of the activated carbon of 217.697 m2/g. However, the composite has magnetic properties with the saturatization magnetization of 17.91 emu/g. The optimum condition of the composite for adsorption of methyl red was obtained at a weight of 0.15 g, and contact time of 100 minutes. The adsorption of the composite was in accordance by pseudo-second-order kinetic and Langmuir isotherms with adsorption capacity of 81.97 mg/g.

The alumina-activated carbon has the ability to adsorb and desorb the procion red MX-5B. The research evaluated the influence of desorption agent, contact time, and temperature on desorption process of procion red MX-5B dye with alumina-activated carbon composite and the adsorption capacity of the composite after desorption process. The desorption agents used in desorption process were solution with pH 2−10, H2O2 30 % (v/v), methanol 70% (v/v) and ethanol 70% (v/v). The variation of contact time was in the range from 30 to 270 min and the temperature was set between 30−75 °C. The result concluded that the highest desorption efficiency up to 98.56% was achieved using ethanol 70% (v/v) for 240 min at 45 °C. The desorption kinetic followed the pseudo-first-order with the release constant (kdes) of 6.56 × 10-2 min-1. The SEM micrograph showed there is a more porous surface on the composite after the desorption compared to before the desorption. The EDX analysis indicated that alumina content in the composite was reduced after desorption process. FTIR spectra of the composite before and after desorption process showed a peak of Al−O at 592 and 590 cm-1 which was proved that alumina still exists in the composite after the desorption process. The alumina-activated carbon composite was re-used to adsorb procion red MX-5B dye. After three times of desorption and re-adsorption process, the capacity adsorption was decreased from 12.38 to 7.38 mg/g.

The aim of the research was to extract a cellulose from kepok banana peel (Musa parasidiaca L.) and application to removal Procion dye. The extracted cellulose was prepared by dewaxing process to releasing of lignin, bleaching and hemicellulose removal. The cellulose identified by FTIR and SEM-EDS. The efficiency of the cellulose to adsorp Procion dye was evaluated by variation in the initial concentration of dye (5, 10, 15, 20, 25, 30, 35, 40, 45 and 50 mg/L), solution pH (3, 4, 5, 6, 7, 8 and 9), and the contact time (15, 30, 45, 60, 75 and 90 minutes) at room temperature. The result showed that FTIR spectra of cellulose from kepok banana peel were similar with FTIR spectra of standard cellulose. The morphology of cellulose more homogenous than kepok banana peel powder. It was observed that the optimum adsorption of Procion dye by cellulose was on the initial concentration of 30 mg/L, pH solution of 5 and contact time within 30 minutes. The obtained result that cellulose has removal percentage to adsorp Procion dye more higher than kepok banana peel powder. The adsorption equilibrium showed the Langmuir isotherm was described well for adsorption process (R2 = 0.991) than Freundlich isotherm (R2 = 0.922).