Sustainable Engineering

Magnetic Spent Tea Leaves as a Sustainable Carrier for Laccase Immobilization in Brilliant Green Removal from Aqueous Solution

Nurmin Bolong — 2026-07-27

Synthetic dyes released into waterways through industrial effluents remain a major environmental concern because of their persistence and potential ecological effects. This study evaluated magnetic spent tea leaves (MSTL) as a low-cost and sustainable carrier for laccase immobilisation and assessed the performance of the resulting material (MSTL-LI) for Brilliant Green removal from aqueous solution. Laccase was immobilised onto MSTL, achieving an activity of 106.4 U/g and demonstrating successful enzyme attachment to the support. The effects of contact time, initial dye concentration, and adsorbent dosage on dye removal were investigated. Dye removal increased with contact time and reached 86.30% at 48 h for 100 ppm Brilliant Green using 50 mg of MSTL-LI, with only marginal improvement at 60 h, indicating that equilibrium had been approached. At the optimized contact time, the highest removal efficiency was obtained at the lowest tested dye concentration (100 ppm), while removal efficiency decreased progressively as the initial concentration increased from 200 to 400 ppm. Increasing the adsorbent dosage from 50 to 200 mg improved removal efficiency from 87.98% to 95.31%, although only marginal additional improvement was observed beyond 150 mg. These findings suggest that MSTL-LI is a promising waste-derived support for dye removal. Nevertheless, further studies involving material characterisation, reusability assessment, and mechanistic investigation are required to further evaluate its practical applicability in wastewater treatment.

Black Soldier Fly as a Sustainable Solution for Converting Slaughterhouse Waste into Compost: Influence of Feed Composition and Larvae Quantity

Rizkiy Amaliyah Barakwan — 2026-03-09

Slaughterhouses play a crucial role in food security but generate substantial organic waste, including rumen content and cattle dung, which contributes to environmental pollution. Bioconversion using Black Soldier Fly (BSF) larvae offers a promising approach for transforming slaughterhouse waste into nutrient-rich kasgot. This study aims to evaluate the efficiency of BSF larval bioconversion in reducing slaughterhouse waste and assessed the quality of the resulting kasgot. The experiment was conducted at the laboratory scale for 15 days, with each reactor containing 400 seven-day-old BSF larvae. Feed composition varied according to rumen-to-cattle dung ratios of 100:0, 80:20, 50:50, and 0:100 (w/w). The feed quantities used were 60, 80, and 100 mg/larvae/day. The results showed that a feed composition of 100% rumen and feed quantity of 100 mg/larvae/day provided optimum results, with a total waste reduction of 78.6%, an Efficiency of Conversion of Digested Food (ECD) of 8.7%, and a total larval growth of 21.71 g. The resulting kasgot met Indonesian standards for solid organic fertiliser, with C-organic, total N, and the C/N ratio ranging from 20.5–38.9%, 1.79–1.92%, and 10.89–20.86, respectively. These findings demonstrate that BSF larvae have strong potential and provide a basis for optimising the composting process as a sustainable waste transformation method.

Preparation, Characterisation, and Application of a Chitosan–Zeolite Adsorbent for Efficient Congo Red Dye Removal from Aqueous solutions

S M Anisuzzaman — 2026-07-29

The presence of synthetic dyes such as Congo red (CR) in wastewater, particularly from the textile industries, poses serious threats to both the environment and human health. These dyes are not only toxic and potentially carcinogenic but are also chemically stable, making them difficult to break down using conventional treatment methods such as coagulation, oxidation, or biological processes. In this study, a chitosan–zeolite adsorbent (CZA) was developed and investigated for the removal of CR from aqueous solutions. The adsorbent was synthesised using a simple mixing method and thoroughly characterised using Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), and Brunauer–Emmett–Teller (BET) surface area analysis. The results confirmed the successful formation of CZA, with relevant functional groups, a semi-crystalline structure, and a porous structure with a surface area of 34.01 m²/g. Batch adsorption experiments were conducted to study the influence of parameters such as pH, contact time, temperature, and adsorbent dosage on dye removal efficiency. The highest dye removal efficiency of 98.4% was achieved using 1.0 g of CZA under optimum conditions of a pH 2, a contact time of 120 min, and 25°C. The adsorption data were analysed using isotherm and kinetic models. Among the isotherm models evaluated, the Langmuir model provided the best fit ( = 0.9980), indicating monolayer adsorption with a maximum adsorption capacity ( ) of 89.29 mg/g. Kinetic modelling showed that the adsorption followed the pseudo-second-order model ( = 0.9966), suggesting that chemisorption was the dominant mechanism. Overall, this study demonstrates that the CZA exhibits high adsorption efficiency and has considerable potential for application in the treatment of dye-contaminated wastewater.

Mixed Matrix Membrane for Hydrogen Recovery: Development, Challenges and Future Outlooks

Noor Maizura Ismail — 2026-07-27

Hydrogen is widely seen as a clean and sustainable energy option but extracting and recovering it efficiently still poses significant challenges. In recent years, membrane separation has gained attention as an effective method for purifying hydrogen due to its promising performance and potential for practical application. Mixed-matrix membranes (MMMs) have gained significant attention among membrane types because of their potential to improve separation performance. This review examines recent progress in innovative MMM materials tailored to enhance hydrogen recovery efficiency. Researchers blend polymers with advanced inorganic fillers like zeolites, metal-organic frameworks (MOFs), and carbon-based materials. The discussion begins with an overview of hydrogen purification and existing MMM technologies. The evolution of material selection and integration of advanced inorganic fillers with compatible polymers was also discussed. This review highlighted the complex interactions between fillers and polymer matrices which play an important role in determining the membrane morphology, stability, and selectivity. Few of MMMs technology separation performance were compared in terms of hydrogen selectivity across various fillers and polymers. Lastly, this work addresses existing challenges such as high temperature, pressure and the presence of contaminants can lead to instability.

Sensitivity Analysis of Torque and Drag in Offshore Extended Reach Drilling Wells Using a Simulation-Based Approach

KAMILIA SHARIR — 2026-07-27

Extended reach drilling (ERD) is widely applied in offshore hydrocarbon development to access distant reservoirs while minimizing surface infrastructure. However, long inclined and horizontal sections in ERD wells increase torque and drag forces, which may lead to stuck pipe, excessive mechanical loading, and reduced drilling efficiency. This study presents a simulation-based sensitivity analysis to evaluate the combined influence of build-up rate (BUR) and bottom hole assembly (BHA) stabilizer configuration on torque and drag behaviour in an offshore ERD well. The novelty of this study lies in the integrated assessment of trajectory curvature and stabilizer configuration under multiple drilling operational conditions rather than evaluating these parameters independently. Well trajectories were generated using COMPASS, and mechanical load analysis was performed using WELLPLAN under run-in-hole, pull-out-of-hole, rotating-on-bottom, and rotating-off-bottom conditions. Three BUR values, namely 2.0°, 2.5°, and 3.0°/100 ft, and three stabilizer configurations consisting of two, four, and six stabilizers were evaluated, resulting in nine simulation scenarios. The results show that reducing BUR from 3.0°/100 ft to 2.0°/100 ft decreased pick-up drag from 82.3 kip to 77.7 kip and slack-off drag from 75.7 kip to 72.9 kip. Although additional stabilizers may increase localized contact points, the six-stabilizer configuration improved drillstring centralization and trajectory stability, resulting in the most favourable torque and drag response when combined with the lowest BUR. The optimal configuration was identified as BUR 2.0°/100 ft with six stabilizers. These findings demonstrate that integrated optimization of trajectory design and BHA configuration can reduce mechanical loading and support safer, more efficient offshore ERD operations.