Wax deposition is a major flow-assurance challenge in oil and gas pipelines, particularly under low-temperature conditions that promote wax crystallization and accumulation. This study developed and evaluated a plant-based cellulose-acetate additive as an environmentally friendly alternative to conventional synthetic wax inhibitors. Cellulose acetate was extracted, formulated, and characterized using FTIR, GC-MS, and GC-FID, while wax-inhibition performance was assessed using a cold-finger wax deposition test and rheological analysis with a rheometer. FTIR confirmed the presence of characteristic functional groups, while Sample A produced at 200 rpm exhibited the most favourable characteristics, with GC-MS abundance profiles and GC-FID retention times closely comparable to those of a commercial inhibitor. The optimum wax-deposition conditions were 100 rpm, 13 °C, and 4 h using 20 mL of 8000 ppm inhibitor, resulting in a minimum wax deposit of 0.16 g. Rheological analysis identified 8000 ppm as the optimum concentration, producing the lowest viscosity of 4.0104 cP at 25 °C. Although this concentration showed a slightly higher interfacial tension (IFT), the increase had minimal influence on inhibition performance. Rice-husk-derived cellulose acetate demonstrated promising potential for reducing wax deposition while maintaining favourable crude-oil flow properties. The study contributes to green chemistry and agricultural-waste valorisation, while further investigation of long-term stability and field-scale performance is recommended. Copyright © 2027 by Authors, Published by Universitas Diponegoro and BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).
The Joule–Thomson (JT) effect is well characterized at engineered throttling devices such as valves, regulators, and leak orifices, but its occurrence at internal weld-joint geometry, an unintentional, workmanship-tolerance-scale feature present at every girth weld, has not previously been established experimentally; existing JT-cooling studies assume an intentional, externally specified throttling geometry, while weld-integrity studies address the erosion, corrosion, and stress consequences of internal weld irregularities without examining their thermal effect. This study addresses that gap by providing controlled experimental evidence of weld-induced JT cooling as a distinct micro-throttling mechanism. The objective was to determine whether internal weld-joint geometry (weld reinforcement and hi-lo misalignment) constitutes a measurable, thermodynamically consistent JT throttling mechanism under representative natural gas transmission conditions. A natural gas pipeline test section incorporating a smooth-pipe baseline and four internal weld geometries (low, medium, and high reinforcement, and hi-lo misalignment) was tested at upstream pressures of 40–70 bar and flow velocities of 5–15 m/s, with the measured response validated against Peng-Robinson-based isenthalpic predictions (ΔT = μJTΔPw) and independent CFD simulation. The CFD simulation reproduced the experimental pressure loss to within an average of 3.5%. Weld-induced pressure loss and the corresponding corrected temperature response increased systematically with geometric severity and flow velocity, reaching a maximum additional pressure loss of 0.199 bar and a maximum corrected temperature reduction of 0.0404 K for the hi-lo geometry at 60 bar and 15 m/s; flow velocity accounted for 55.96% of the variance in the response, followed by weld geometry (26.62%) and their interaction (13.84%), and a regression model linking temperature response to weld severity, velocity, and pressure achieved R² = 0.9642. These results confirm that internal weld geometry constitutes a genuine, thermodynamically consistent local JT throttling mechanism, one that is two to three orders of magnitude smaller than the cooling associated with engineered throttling devices and unlikely to present a significant hydrate, embrittlement, or corrosion hazard at an isolated girth weld. Copyright © 2027 by Authors, Published by Universitas Diponegoro and BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).
Biodiesel is a sustainable alternative to petroleum diesel, but developing efficient, low-cost, and environmentally friendly heterogeneous catalysts remains challenging. This study investigated biodiesel production from crude palm kernel oil using a composite calcium oxide catalyst derived from waste eggshells and snail shells. The catalyst was calcined at 900 °C for 3 h and characterized by XRD and FTIR, confirming predominantly crystalline CaO with minor Ca(OH)₂ and carbonate species. Response Surface Methodology using a Central Composite Design optimized reaction time, temperature, catalyst loading, and methanol-to-oil ratio. The quadratic model was significant (F = 60.25, p < 0.0001) and demonstrated high predictive capability (R² = 0.9825, Adjusted R² = 0.9662, Predicted R² = 0.9099). Optimum conditions of 82.5 min, 60 °C, 5.5 wt% catalyst, and 6:1 methanol-to-oil ratio yielded 91.273 wt% biodiesel. The composite catalyst outperformed calcined eggshell (87.0 wt%) and snail shell (85.5 wt%) catalysts under identical conditions. Biodiesel properties complied with ASTM specifications, with acid value of 0.431 mg KOH.g⁻¹, flash point of 129 °C, and dynamic viscosity of 4.53 mPa.s. The findings demonstrate the catalyst's potential for sustainable and low-cost biodiesel production while promoting agricultural waste valorization without the need for further catalyst modification. Copyright © 2027 by Authors, Published by Universitas Diponegoro and BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).
Growing plastic waste and industrial wastewater necessitate sustainable treatment solutions. This study optimized industrial wastewater treatment using activated carbon derived from high-density polyethylene (HDPE) pyrolysis char via thermal activation, eliminating the need for aggressive chemical agents. Characterization via FTIR, BET, and SEM-EDX revealed a micro-mesoporous structure with a BET surface area of 287.3 m²/g, a 90.05 atomic percent carbon content, and dominant pore sizes of 2.1 to 2.6 nm. The adsorbent performance was evaluated against laundry wastewater using a Central Composite Design and Response Surface Methodology. Statistical analysis yielded a robust model (R² = 0.9406, adequate precision = 15.54) to assess the impact of dosage, contact time, and initial concentration. Numerical optimization identified ideal conditions: 8.68 g/L dosage and 15-minute contact time for a 100 mg/L initial concentration. Experimental validation confirmed a 77.99% total dissolved solids (TDS) reduction, aligning closely with the predicted 79.48%. Post-treatment analysis indicated significant quality improvements, with COD and TOC levels decreasing to 35.8 mg/L and 21.6 mg/L, respectively, while dissolved oxygen increased from 0.6 to 4.3 mg/L. This research confirms that HDPE-derived activated carbon offers an effective, sustainable approach for both wastewater remediation and plastic waste valorization. Copyright © 2026 by Authors, Published by Universitas Diponegoro and BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).
Conventional enhanced oil recovery (EOR) methods often lose effectiveness under high-temperature, high-salinity (HTHS) conditions because of inadequate fluid stability, limited wettability alteration, and insufficient interfacial tension (IFT) reduction. This study developed and evaluated cellulose nanoparticles (CNPs) derived from Acacia auriculiformis as a sustainable nanofluid for EOR. CNPs were extracted using a deep eutectic solvent (DES) process and surface-modified to improve thermal stability and interfacial functionality. Structural, morphological, compositional, and thermal characteristics were evaluated, while the resulting cellulose nanofluid (CNF) was assessed through rheology, IFT, contact-angle, and sand-pack flooding experiments. The process yielded 78.3% CNP, with an average particle size of 19.65 ± 0.2 nm and crystallinity index (CrI) of 76.6%, confirming successful formation of crystalline nanocellulose. At 0.2 wt%, CNF reduced oil-water IFT to approximately 7.8 mN/m at elevated temperature and decreased the sandstone contact angle to 16.5°, indicating strong water-wet alteration. Sand-pack flooding achieved 13.7% incremental oil recovery and 72.3% total recovery, compared with 9.8% incremental recovery and 63.1% total recovery for xanthan. The superior performance is attributed to the combined effects of IFT reduction, wettability alteration, mobility control, and thermal stability. Overall, Acacia-derived CNF demonstrates greater EOR potential than xanthan and represents a promising, environmentally sustainable nanofluid for challenging reservoir conditions. Copyright © 2026 by Authors, Published by Universitas Diponegoro and BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).
