Engineering Chemistry Vol. 8

Abstract: Increasing textile production leads to a corresponding rise in dye waste, including substances such as methylene blue. Methylene blue poses a significant environmental challenge due to its non-biodegradable nature and high toxicity, which can adversely affect both human health and ecosystems. To address this issue, various methodologies have been explored, with adsorption emerging as a promising technique. This study focuses on employing adsorption utilizing an adsorbent derived from patchouli dregs and activated using hydrochloric acid (HCl). The research commenced with the pyrolysis of patchouli dregs at different temperatures: 300°C, 340°C, and 380°C for 1.5 hours. Subsequently, chemical activation was carried out using HCl solutions with concentrations of 0.3 M, 0.5 M, and 0.7 M. The resulting activated adsorbent underwent characterization to assess its morphological structure, functional groups, and crystalline composition. The scanning electron microscopy (SEM) analysis revealed prominent pores in the patchouli dregs adsorbent post-activation, with a size of 14.699 μm. X-ray diffraction (XRD) analysis demonstrated an irregular microcrystalline structure and amorphous nature of the activated patchouli dregs adsorbent. Additionally, Fourier transform infrared (FTIR) analysis identified active functional groups including O-H, C=O, C=C, C≡C, and C=H, which facilitate methylene blue adsorption. Characterization of the various iterations of the patchouli dregs adsorbent confirmed its suitability for methylene blue adsorption, meeting the quality standards outlined in SNI 06-3730-1995. These standards include a water content of 1.935%, ash content of 7.568%, and iodine adsorption capacity of 1,270.41 mg/g. In summary, this study elucidates the potential of patchouli dregs-derived adsorbents activated with hydrochloric acid for effective methylene blue removal, providing insights into their morphological, structural, and functional characteristics crucial for addressing the challenges associated with textile dye waste management.

Abstract: Clay minerals possess substantial potential for developing innovative functional materials, particularly in the context of environmental protection. This study focuses on the adsorbent zeolite-clay and bentonite-clay, shaped into honeycomb monoliths to efficiently remove Fe²⁺ ions from water. The process involved physically activating powdered zeolite-clay and bentonite-clay through calcination at 600°C. The activated materials were then mixed with distilled water and molded into monolithic shapes through extrusion with stainless steel molds, resulting in cylindrical structures measuring 1.8 cm in diameter and 2 cm in height, featuring 40 perforations. Mechanical characterization aimed to evaluate structural strength and assess pressure drop during operation, revealing superior mechanical strength in bentonite-clay compared to zeolite-clay. The monolithic form exhibited lower pressure drop during operation compared to pellet adsorbents. In terms of adsorption performance, a batch reactor assessed efficiency, isotherm, and kinetics with 2 and 4 ppm Fe2+ ion solutions over a 240-minute period. The zeolite-clay monolith demonstrated the highest capacity, achieving a removal efficiency of up to 65%. Maximal adsorption capacities for bentonite-clay and zeolite-clay were 0.209 and 0.289 mg/g, respectively, with corresponding Langmuir adsorption equilibrium constants (KL) of 0.187 and 0.181 L/g by the Langmuir isotherm model. Kinetic analysis favored the pseudo-first-order non-linear model, indicating rates for zeolite-clay and bentonite-clay adsorbents at 2 and 4 ppm Fe²⁺ ion concentrations of 0.0043, 0.0030, 0.0039, and 0.0038 min^-1. This study signifies a significant advancement in solid adsorbents, optimizing the adsorption process for broader applications.

Abstract: This study focused on the oil absorption and carbonization regeneration properties of expanded graphite (EG) prepared from commercial expandable graphite as an oil absorbing material for different oils. The specific surface area of the prepared EG sample was 37.15 m²/g, and the oil absorption was as high as 76 g/g. More importantly, the prepared expanded graphite had excellent recyclability and good carbonization regeneration performance. Even after 5 cycles, the adsorption capacity remained above 80%. The regenerated EG sample regained a high oil absorption capacity of 44.64g/g. This article has important guiding significance for promoting the large-scale practical application of expanded graphite oil absorbing materials.

Abstract: The investigation of kinetics is crucial for optimizing the adsorption process, particularly in multicomponent systems where several adsorbates compete for active sites on the adsorbent particle. This study presents a novel approach to improve the pseudo-first-order and pseudo-second-order kinetic models by integrating a competition parameter. This parameter quantifies the influence of the adsorbate interaction on the adsorption process. Empirical data of binary adsorption involving doxycycline (DXC) and tetracycline (TTC) were used to validate the improved models. The results indicate that the adjusted pseudo-first-order and pseudo-second-order kinetic models effectively depict the adsorption kinetics when the R² values ​​approach unity. The competition factor, denoted by the parameter α, quantifies the degree to which one adsorbate affects the adsorption capacity of the other. This study indicates that the revised models offer a more thorough understanding of adsorption kinetics in multicomponent systems, thereby facilitating more effective selection of adsorbents and optimization of the process.

Abstract: Graphene oxide has drawn attention globally as it emerged as a promising adsorbent material with enhanced adsorption of environmental pollutants due to its eco-friendly attributes, high surface area, and cost-effectiveness for mass production. This economical solution is a promising and potentially transformative approach to heavy metal removal, contributing to a cleaner and more sustainable future. In this study, unmodified and modified graphene oxide were examined for the removal of copper (II) ions in an aqueous solution. Modified Hummer’s method was utilized to synthesize the graphene oxide. The synthesized graphene oxide was then modified with N- trimethoxysilylpropylethylenediaminetriaceticacid (EDTA-silane), resulting in EDTA-modified graphene oxide (EGO). Batch adsorption tests were done for both adsorbents in order to determine the effects of various factors, such as pH, adsorbent dosage, and contact time. Additionally, in order to describe the adsorption behavior of the adsorption system, it was further fitted to isotherm and kinetic adsorption models. Results of adsorption study showed optimum adsorption for copper (II) ions was achieved at pH = 7, contact time = 45 min, and adsorbent dosage of 5 mg and 4 mg of unmodified graphene oxide (GO) and modified graphene oxide (EGO), respectively. The fundamental mechanism of both adsorbents was best explained by Langmuir isotherm model and the pseudo-second-order model, indicating that the adsorption system followed chemisorption. The adsorption capacity and maximum removal of copper (II) ions was 672.22 mg/g and 78.41% for GO, and 729.11 mg/g and 89.94% for EGO. The latter suggested that graphene oxide treated with EDTA-silane (EGO) has the higher capacity to adsorb copper (II) ions.

Abstract: Carbon dioxide is a dangerous pollutant that harms the environment and triggers global warming, which causes greenhouse gases. Serpentine is a rock rich in magnesium silicate, which can be used to reduce carbon dioxide pollutants through adsorption technology. Aceh Province has the potential for serpentine rocks, which can be processed to adsorb carbon dioxide pollutants. This research examines the characteristics of serpentine based on its morphology and chemical composition as a carbon dioxide adsorbing material. The serpentine aceh was obtained from Indrapuri Regency, Aceh Province. The thermal activation stage is as follows: serpentine aceh is collected, cleaned, reduced in size, and dried, then serpentine aceh is ground to a size of 50 mesh (297–149 µm), 100 mesh (149–94 µm) and 150 mesh (94–74 μm). The serpentine aceh was thermally activated using a furnace at 750 °C for 1.5 hours for all particle sizes. The characterization of serpentine aceh, which consists of morphological and chemical structure analysis using scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) and chemical composition using X-ray fluorescence (XRF). The results show that the characteristics of serpentine aceh before being activated have a lizardite and chrysotile structure with a chemical composition of SiO₂ 38.83% and MgO 29.95%, and after being thermally activated, serpentine aceh has an antigorite structure with a chemical composition of SiO₂ 45.42% and MgO 36.83% at 150 mesh. This research contributes to utilizing one of Aceh's natural mineral resources, serpentine rock, as an alternative CCS material to reduce greenhouse gas emissions.

Abstract: Determination of the optimum composition of chitosan-grafted cellulose/TiO₂ film was performed using the Box-Behnken Design method from Response Surface Methodology (RSM). Apart from being able to determine the best composition for a composite, this method can also determine the influencing factors of the composition on the performance of the composite. This method was conducted by combining factorial group design. This design used three factors and three levels. Adsorption capacity data from the adsorption process and percent removal from the photocatalyst process were used as responses in determining the optimum composition of chitosan-grafted cellulose/TiO₂ films. Based on the results, the counterplot of grafted cellulose vs TiO₂ shows that both variables have the same influence, where the more grafted cellulose and TiO₂ added to the composite, the more adsorption capacity of the chitosan-grafted cellulose/TiO₂ film. The results from determining the composition, obtained the best composition, namely chitosan; grafted cellulose; TiO₂ each of 0.85; 0.2; 0.2 g.

Abstract: Color analysis using colorimetric detection has shown significant advancements, although it still faces challenges when capturing color images under varying illumination conditions. This study explores the utilization of the HSV (hue, saturation, value) color model for precise color analysis, enabling the differentiation of colors based on their type, intensity, and brightness without being affected by illumination. The HSV model, measured by the Euclidean Distance (ΔE) value, is employed to investigate the impact of fluoride solution pH and concentration on the colorimetric detection process of fluoride ions using a thiourea receptor. The colorimetric detection of fluoride ions at low and high pH levels decreases ΔE values and notable color changes. Additionally, the HSV model elucidates the color variations induced by fluoride concentration and demonstrates a linear relationship up to 0.9809.