-Synthetic dye wastewater from textile industries is characterized by strong color, high temperature, variable pH and high chemical oxygen demand (COD). The strong color of wastewater affects aesthetic and water transparency of water bodies. One of method that has advantages in term of simplicity to remove synthetic dyes is adsorption. Two different biomaterial wastes of rice straw and palm oil midrib were used in this study to develop activated carbon adsorbents. These adsorbents were applied for the removal of Naphtol AS-G dye in aqueous solution. The effects of solution pH, adsorbents masses and contact time on dye adsorption were evaluated based on batch experiments. Removal of dye can be achieved within 60 minutes at a wide pH range starting from 4 to 8. At lower pH, synthetic dye removal was decreasing probably due to protonation of adsorbent's active sites. The adsorption isotherms based on Langmuir and Freundlich models were analyzed. The isotherms analysis indicated that the adsorption by rice straw and palm oil can be represented by Langmuir and Freundlich isotherm model, respectively. Adsorption isotherms of Naphtol AS-G onto activated carbon are favorable with high adsorption capacity for both biomaterials. The mechanisms of color removal by activated carbon involved chemical and physical adsorption, in accordance with both the Langmuir and Freundlich models. The calculated maximum dye adsorption capacities onto rice straw and palm oil midrib activated carbon were 55.86 and 69.44 mg/g, respectively. Adsorption using biomass-based activated carbon offers a good technique for textile wastewater treatment as it could remove up to 95% of the color intensity besides reducing other pollutants such as COD, nitrate and phosphate.

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Synthesis of silver nanoparticles, as potential mercury metal detection, using Lamtoro Pods extracts has been successfully carried out by the green reduction method. The peak spectrum of plasmon resonance (SPR) at 415 nm confirmed the formation of silver nanoparticles. The Fourier transform infrared (FTIR) test obtained a characteristic functional group vibration spectrum in Lamtoro Pods. A shift of wavenumber was distinguished by comparing the FTIR spectrum between Lamtoro pods extract and silver nanoparticles. This indicated the involvement of phenol and flavonoid compounds found in the Lamtoro act as a reducing agent of Ag + to Ag 0 (silver nanoparticles). The X-ray diffractometer (XRD) pattern showed that the material synthesized as silver nanoparticles. The transmission electron microscopy (TEM) characterization showed that the nanoparticles have an average size 15.70 nm. The color intensity of silver nanoparticles decreased to be colorless after being contacted with mercury ion, indicating its potential for mercury metal ions detection.

In this study, the effectiveness of Ce(III) ions adsorption in aqueous solution was investigated by modifying sodium alginate with magnetite nanoparticles. The magnetite nanoparticles were coated with sodium alginate (Alg-Fe 3 O 4 nanoparticles), which was prepared by the co-precipitation method.The average size of the Alg-Fe 3 O 4 nanoparticles was 13.70 nm. The optimum conditions for the adsorption process were found at pH 4, 4 hours of contact time and 0.15 g of adsorbent dosage in the batch condition. The adsorption process of Ce(III) ions followed the Langmuir isotherm. The kinetic data indicated that the intraparticle diffusion process was pseudo-second order with maximum adsorption capacity (q m ) of 31.83 mg g À1 . From this experiment, it can be concluded that Alg-Fe 3 O 4 nanoparticles had good reusability shown by their adsorption-desorption ability using 0.01 M HNO 3 as the desorption agent.

The Magnetic compound, Fe3O4, is one of the compounds that is easily hydrolyzed and oxidized. A coating method was presented in this study to prevent the process. The modifications of Fe3O4 were carried out by supporting alginate as natural polymers on the surface of Fe3O4. Preparation of magnetic alginate/Fe3O4 (Alg/Fe3O4) nanocomposite has been successfully synthesized. Alg/Fe3O4 material was synthesized using the coprecipitation method with Fe2+; Fe3+ (with molar ratio 1:2) and alginate 1% as precursors. Synthesized Alg/Fe3O4 nanoparticles were characterized by Fourier Transform Infrared Spectroscopy (FTIR), DelsaTM Nano C Particle Analyzer, Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), and Energy Dispersive Spectroscopy (EDS). The Alg/Fe3O4 has an average diameter of 13.70 nm. Photodegradation test of synthetic methylene blue (MB) dye was found at pH 5.0 and irradiation time under UV245 for 60 minutes. The degradation results showed that the percentage of MB dye removal reached more than 90%.