Dye wastewater treatment with rice husk-derived silica xerogel: An eco-friendly process

Removal of dye contamination from wastewater is crucial for protecting human health and the environment, and adsorption is considered an effective removal method. In addition, agricultural residues are attractive for use as adsorbents for the adsorption due to their renewability. Therefore, the present work aimed to develop silica xerogel from rice husk (agricultural residue in rice production) into an adsorbent for dye wastewater treatment. In the xerogel synthesis, a non-toxic organic acid (citric acid) was used instead of a toxic inorganic acid for leaching and precipitation steps to lower the environmental impact of the process. It was found that the obtained silica xerogel has physical properties such as a surface area and pore volume, comparable with silica xerogels in other literature. When applying it in the dye (methylene blue) wastewater treatment, the obtained silica xerogel showed better adsorption capacity than unprocessed silica at all studied conditions, i.e. various times, pH and initial concentration. The maximum adsorption capacity of the xerogel and unprocessed silica were 103.45 and 61.78 mg/g, respectively. This indicates the benefit of silica xerogel with low environmental impact when applied in dye wastewater treatment. The adsorption isotherms and kinetic for both types of silica were also conducted. It was found that the adsorption process of methylene blue on the silica fitted the Langmuir adsorption isotherm and followed the pseudo-second-order kinetic model. This provides valuable information for optimizing the operating parameters for best performance in a given situation.

การผลิตและคุณลักษณะของแบคทีเรียลเซลลูโลสที่ผลิตด้วย Acetobacter xylinum TISTR 978 จากน้ำคั้นเปลือกสับปะรด

วารสารวิชาการและวิจัย มทร.พระนคร, 13(1) : 180-192This research studies the production of bacterial cellulose from Acetobacter xylinum TISTR 975 with pineapple peel juice, a low cost carbon source, and coconut water as nutrient and carbon source. The factors influencing the production were studied including incubation time, type of carbon sources and ratio of mixed carbon sources. In addition, the characteristics of the produced bacterial cellulose were investigated using Fourier Transform Infrared Spectrophotometer (FTIR), Scanning Electron Microscope (SEM), Thermogravimetric Analyzer (TGA), Differential Scanning Colorimeter (DSC) and x-ray Diffractometer (xRD). It was found that the coconut water produced the amount of bacterial cellulose higher than the pineapple peel juice with 10 days of production. An addition of the coconut water into the pineapple peel juice increased the amount of bacterial cellulose. The characteristics of two bacterial celluloses from two different sources were nearly similar but the one from the pineapple peel juice had higher impurities. It can be concluded that the pineapple shell extract could be used as low cost carbon source for bacterial cellulose production.Rajamangala University of Technology Phra Nakho

Effect of Particle Size of Rice-Husk Derived Silica on the Pyrolysis of Pomelo Peels

Silica with two different sizes i.e. microsilica (MS) and nanosilica (NS) was used as a catalytic support for vanadium (5-15 wt%) in the pyrolysis of pomelo peels. Besides use of pomelo peels (agricultural residues) as a feedstock for the pyrolysis, to contribute to environmental sustainability, rice husk was used as a silica source for obtaining the silica support. From the result, it was found that non-catalytic pyrolysis of pomelo peels gave a bio-oil yield of 33.3 wt%. The catalytic pyrolysis with vanadium-modified silica decreased the bio-oil yields ranging between 27.2-33.1 wt%. This was due to the occurrence of the second reactions generated from the active sites on the catalysts, which leads to the conversion of bio-oil into gas products. For NS catalyst, increasing the amount of vanadium loading directly decreased the bio-oil yields and increased the gas yield. The variation of product phase distribution was not clearly observed for MS catalyst even with various vanadium loadings. In addition, NS catalyst exhibited higher efficiency in reducing the acid content in the bio-oil, and increasing the phenol content. The distinguished properties of the nanoparticles may be the main reason for these phenomena. Copyright © 2023 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0)

การดูดซับสีย้อมเมทิลีนบลูบนถ่านกัมมันต์ที่เตรียมจากกากน้ำตาลโดยวิธีการกระตุ้นด้วยสารเคมีและไมโครเวฟ

วารสารวิชาการและวิจัย มทร.พระนคร, ปีที่ 15, ฉบับที่ 1 (ม.ค.-มิ.ย. 2564), หน้า 167-178This research aims to produce activated carbon from molasses via a chemical activation process with potassium hydroxide (KOH) and a microwave heating process, which consumes less energy and provides more rapid and uniform heat distribution than a conventional heating. The obtained activated carbon was then characterized with BET, SEM and FTIR. It exhibited a large specific surface area of 1,631 m2/g, and a total pore volume of 1.124 cm3/g consisting of mesopore and micropore. In addition, the active functional groups were also found on the surface of the activated carbon. Thus, it was brought for the adsorption test with methylene blue. It was found that the adsorption capacity of the activated carbon increased with time and reached the equilibrium within 8 hours. The adsorption data of the activated carbon were corresponded to Langmuir isotherm with the highest adsorption capacity of 370.37 mg/g. The adsorption kinetic of the activated carbon exhibited pseudo-second order reaction suggesting to the chemisorption phenomenon. From the thermodynamic study, it revealed that the adsorption process were endothermic and spontaneous reactions.Rajamangala University of Technology Phra Nakho