Jurnal Rekayasa Proses

The Hydrothermally synthesized hydroxyapatite from ale-ale shells as a bone graft material alternative

Tyas Galuh Amelia — 2026-06-09

Ale-ale shells (Meretrix meretrix), a locally abundant shellfish waste in West Kalimantan, Indonesia, were investigated as a sustainable calcium precursor for the hydrothermal synthesis of hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂), the primary inorganic constituent of bone widely used in graft applications. Synthesis was conducted under varying reaction times (16–24 hours) and temperatures (140–180°C). FTIR and XRD analyses confirmed the formation of hexagonal-phase hydroxyapatite consistent with the JCPDS 09-0432 standard, with characteristic hydroxyl and phosphate functional groups detected and minor carbonate incorporation (1.00–1.52%), remaining well below the 8% limit for bone implant applications. The optimum condition was identified at 160°C for 20 hours, yielding nano-scale hydroxyapatite (14.50 nm) with high crystallinity (98.90%), satisfying ISO 13779 requirements. These findings highlight the potential of ale-ale shell-derived hydroxyapatite as a viable, locally sourced alternative to imported biomaterials while supporting the sustainable valorization of Indonesian shellfish waste.

Characterization of caffeine crystals obtained from the extraction process of green robusta coffee beans

Tri Hariyadi — 2026-06-09

Robusta coffee contains a higher caffeine content, ranging from 1.6–2.4%, nearly twice as much as Arabica coffee, which contains only 0.9–1.2%. Caffeine content is widely utilized in various fields, such as pharmaceuticals and the food and beverage industry. This study aims to analyze the effect of temperature and time on the solid–liquid extraction process of green coffee beans, as well as to evaluate the effectiveness of two different solvents in the liquid–liquid extraction process for obtaining caffeine crystals. Solid–liquid extraction was carried out at temperature variations of 70°C, 80°C, 90°C, and 97°C, with durations of 30 minutes, 45 minutes, 60 minutes, 75 minutes, and 90 minutes. Liquid–liquid extraction was performed using two types of organic solvents, namely chloroform and dichloromethane. The results were analyzed by measuring caffeine purity using a melting point apparatus and high-performance liquid chromatography (HPLC) based on retention time parameters, as well as determining caffeine concentration using a UV–Vis spectrophotometer. The optimum temperature and time for solid–liquid extraction were found to be 97°C for 60 minutes. Liquid–liquid extraction yielded a caffeine content of 2.18 mg/g using chloroform, and 1.38 mg/g using dichloromethane. Based on melting point and HPLC retention time testing, the caffeine crystals obtained from liquid–liquid extraction with dichloromethane showed higher purity, with a melting point of 236°C and a retention time of 2.06 minutes. These values are close to those of pure caffeine, which has a melting point of 236°C and a retention time of 2.01 minutes, compared to the caffeine crystals obtained using chloroform.

Optimization of energy performance in a pilot-scale biofilm anaerobic reactor through feedstock composition control of limonene-containing fruit waste

Fajar Marendra — 2026-06-09

Fruit waste containing citrus fractions with high limonene content presents a particular challenge for anaerobic digestion (AD) due to the inhibitory effects of this terpene on methanogenic microorganisms. This study evaluates the performance of a pilot-scale biofilm anaerobic reactor treating mixed fruit waste with varying proportions of citrus residues, focusing on biogas production, methane composition, and process stability. A 1,167 L fiberglass reactor equipped with K1 biofilm carriers was operated under mesophilic conditions and fed with six different substrate formulations. The results indicate that increasing the proportion of citrus waste leads to reduced biogas production during the initial phase, accompanied by volatile fatty acid (VFA) accumulation and pH suppression, suggesting process inhibition driven by limonene. In contrast, formulations with moderated citrus content showed improved operational stability, characterized by pH values of 6.8–7.1, VFA/alkalinity ratios below 0.30, and higher methane fractions. Energy conversion analysis revealed that treatments with controlled limonene levels yielded the highest net energy output, while excessive citrus content decreased conversion efficiency. Correlation analysis confirmed strong associations between VFA accumulation, pH decline, and reduced methane concentration under high-limonene conditions. These findings demonstrate that managing the proportion of citrus-rich fruit waste is essential for maintaining process stability and enhancing biogas productivity in pilot-scale biofilm AD systems.

Synthesis of bioplastic from sago starch with the addition of waste paper-derived cellulose and glycerol–sorbitol plasticizer

Wiza Ulfa Fibarzi — 2026-06-09

Bioplastics are natural-based plastics that can degrade in the environment, making them more eco- friendly. Paper waste contains cellulose with potential as a raw material for bioplastic production. This study aimed to analyze the properties of cellulose-based bioplastics derived from paper waste with the addition of sago starch and plasticizers. The manufacture of bioplastics used a variation treatment of cellulose additions of 1 gram, 2 grams, 3 grams, and without cellulose, and a plasticizer (glyserol + sorbitol) volume of 2 ml, 3 ml, 4 ml, and 5 ml. Characterization included swelling (water absorption), tensile strength, biodegradability, and thermal stability tests. Functional groups of the extracted cellulose were also examined. The extracted cellulose was characterized using FTIR and showed characteristic functional groups of cellulose, such as O–H, C–H, and C–O–C. Swelling tests showed that most bioplastic samples had values below 30 %, indicating good water resistance according to standard criteria (≤30 %). The lowest swelling was observed in samples without cellulose and with 5 mL plasticizer (15.78 %), while the highest occurred in samples with 3 g cellulose and 2 mL plasticizer (42.69 %). The best composition was obtained with 3 g cellulose and 5 mL plasticizer, giving optimal mechanical properties: tensile strength 4.08 MPa, Young’s modulus 74.85 MPa, and elongation 5.74 %. At this formulation, swelling was only 29.50 %, confirming good water resistance. Biodegradability testing also confirmed that all samples exhibited good decomposition ability in accordance with SNI 7188.7:2016 standards.Overall, the utilization of cellulose derived from paper waste combined with glycerol–sorbitol plasticizers successfully produces bioplastics with adequate mechanical properties, controlled water resistance, and high biodegradability. This formulation demonstrates strong potential as an environmentally friendly packaging material to replace conventional plastics.

Synthesis and characterization of alkyd resin based on palm fatty acid distillate (PFAD) modified with vegetable oil

Desi Nurandini — 2026-06-09

Coating industry is currently in urge to produce environmentally friendly products based on considerations of maintaining ecological stability. However, the coating industry, utilizing synthetic alkyd resins, generates substantial emissions of hazardous volatile organic solvent component, while its waste presents degradation challenges. Therefore, innovations are required to coating material from renewable and eco-friendly alkyd resins. Modifying alkyd resins with natural ingredients, such as vegetable oils and fatty acids, potentially enhances their performance as coating material. This research utilizes palm fatty acid distillate (PFAD), a byproduct of palm oil (CPO) processing, as a renewable material for alkyd resin. The use of vegetable oil to modify alkyd resin improves characteristics of the product. Drying-vegetable oil solidifies and hardens through a chemical reaction in which its components cross-link and form a tough, solid film due to oxidation upon exposure to the air. This research aims to study the synthesis process of PFAD-based alkyd resin modified with vegetable oil and investigate the effect of type and composition of modified oil on the characteristics of PFAD-based alkyd resin and its performance as coating material. In this research, PFAD, glycerol, and phthalic anhydride were reacted through a one-step polyesterification process (fatty acid process) at a temperature of 240°C for 4 hours. Modification was conducted by adding vegetable oil at various compositions (a comparison was carried out using several types of drying oil including candlenut oil, linseed oil, and tung oil). The alkyd resin product was characterized by determining its acid value, iodine value, and FTIR analysis, alongside evaluating its curing performance (drying speed) in application as a coating material. The best formulation for the characteristics qualified according to the Standar Nasional Indonesia (SNI 06-0504-1989) are alkyd resins with composition of 50% weight linseed oil (AR-LO-50) and composition of 50% weight tung oil (AR-TO-50) modification, i.e. acid value of 4.6 mgKOH/g sample and iodine number of 119.20 gI₂/100 g for linseed oil, then acid value of 8.31 mgKOH/g sample and iodine number of 102.44 gI₂/100 g for tung oil. The curing test results confirmed that the modified product meets the required 1-day drying time standard.