IPTEK The Journal of Engineering

Comprehensive Study on Cr(VI) Adsorption and Regeneration Behavior of Alkali-Treated Wood Charcoal: Isotherms and Kinetics Models

Moh. Azhar Afandy — 2025-09-02

The present study considers the adsorption and regeneration behavior of alkali-treated wood charcoal (WC-NaOH and WC-KOH) for Cr(VI) removal. Adsorption isotherms (Langmuir, Freundlich, Temkin, and Dubinin-Raduskevich) and kinetics (Pseudo-first-order and Pseudo-second-orderare being investigated utilizing a non-linear method that provides precise parameter prediction and mechanism elucidation. The outcomes suggested that both WC-NaOH and WC-KOH exhibit good Cr(VI) removal efficiency, with the Langmuir model best explaining the adsorption phase, indicating single-layer adsorption. The kinetic study revealed that the Pseudo-second-order model aligns remarkably well with the data, thereby affirming that chemical adsorption is the predominant mechanism in consideration. A comparative analysis revealed that WC-KOH exhibits a higher amount of adsorption than WC-NaOH, attributable to its enhanced larger surface area as well as micro-porous structure.. Regeneration studies showed the possibility of reuse of both adsorbents. It shows the efficiency of alkali-treated wood charcoal for Cr(VI) decontamination and the advantages of non-linear modeling in adsorption experiments.

Application of Electrocoagulation in Stabilizing pH and Removing Pollutants from Domestic and Urban Wastewater Using Aluminum Electrodes

Ardista Izdhihar Kaloka — 2025-09-02

This study investigates the application of electrocoagulation using aluminum electrodes to stabilize pH and remove pollutants from various real wastewater sources in Surabaya, Indonesia, including laundromats, fast food restaurants, campus canteens, mechanical workshops, and tofu industries. A batch-mode electrocoagulation process was conducted using 10 A of current over 60 minutes, and the performance was evaluated based on pH changes, turbidity, and Total Suspended Solids (TSS) removal. The highest TSS removal efficiency of 98% was observed in machine shop wastewater, while laundromat samples also achieved high performance with 97% reduction. Electrocoagulation demonstrated strong pH stability in effluents with buffering compounds such as those from campus canteens and workshops, whereas fluctuating pH and turbidity levels were found in tofu and fast-food effluents, indicating the need for process optimization. Turbidity decreased significantly across all samples, confirming effective floc formation during electrolysis. The findings confirm that electrocoagulation is a promising method for treating both domestic and urban wastewater. However, integrating additional processes such as adsorption or filtration is recommended to enhance performance for complex wastewater compositions and ensure compliance with discharge standards.

Green Synthesis of Microcrystalline Cellulose from Cabbage Waste (Brassica Oleracea L.) Using Steam Explosion and Low-Concentration Chemical Treatment

Nesha Permata Syafira — 2025-09-02

The increasing generation of agricultural waste presents both environmental challenges and opportunities for the development of sustainable materials. This study explores the extraction of microcrystalline cellulose (MCC) from cabbage waste using a combination of steam explosion and low-concentration chemical treatments to optimize lignocellulose degradation. The process involved sequential delignification with NaOH, bleaching with NaOCl, and steam explosion applied to samples that had been soaked in oxalic acid at varying concentrations (0%–2%). After drying, the samples were analyzed using FTIR, XRD, and SEM to evaluate the extracted MCC product. The analytical results showed that the applied method significantly increased cellulose purity, from 31.05% in untreated fibers to 69.88% after steam explosion following soaking in 2% oxalic acid. FTIR analysis confirmed the removal of lignin and hemicellulose, while XRD analysis indicated an increase in crystallinity from 39% to 57%, suggesting improved structural integrity. SEM analysis revealed enhanced fiber separation and reduced particle size, indicating efficient defibrillation. These results highlight the potential of an environmentally friendly approach to producing high-quality MCC, supporting green chemistry principles and sustainable development goals (SDGs). eThe extracted MCC holds promising applications, particularly as a biopolymer for drug delivery systems, polymer composites, and food additives.

Computational Study on Urea Concentration Profiles in Hemodialysis Hollow Fiber Membranes Under Different Blood Flow Conditions

Belinda Kezia Purwanto — 2025-09-02

Kidney failure significantly impairs physiological functions, primarily due to the accumulation of urea in the bloodstream. When renal function drops below 75%, hemodialysis becomes a crucial therapeutic intervention. This study investigates the performance of a hollow fiber dialyzer, consisting of a shell-side dialysate flow, a semi-permeable membrane, and internal capillaries for blood flow. The main objective is to develop a theoretical model describing urea mass transfer through the membrane during hemodialysis. The analysis focuses on the effect of blood flow rate on urea concentration distribution across the tube, membrane, and shell regions in both axial and radial directions. Additionally, the influence of membrane length and dialysate flow rate on urea clearance is examined. Simulation results indicate that higher blood flow rates lead to elevated urea concentrations at the tube outlet, suggesting reduced diffusion into the dialysate compartment. In contrast, increasing membrane length enhances urea clearance. Interestingly, the dialysate flow rate shows minimal impact on clearance efficiency. Under a fixed dialysate flow rate of 500 mL/min and a membrane length of 27 cm, the calculated urea clearance values were 21.95%, 17.06%, 14.31%, and 12.52% for blood flow rates of 200, 300, 400, and 500 mL/min, respectively.

Effect of Inhibitor Addition, pH, and Current Density on the Corrosion Rate of Fe Metals

Anisa Fatma Aulia — 2025-09-02

Corrosion significantly impacts public safety and the economy, causing substantial financial losses, infrastructure damage, and hazardous incidents across various industries. Researchers investigated the effects of pH, current density, and corrosion inhibitors (potassium chromate and potassium nitrate) on iron corrosion by measuring weight loss of iron samples immersed in sulfuric acid over time. The addition of inhibitors showed that KNO3 was more effective in reducing the corrosion rate, with values of 4.992068, 3.744051, 2.736034, 1.728017, and 0.608008 mils per year, compared to K2CrO4, which resulted in 9.728132, 7.296099, 5.472066, 3.648033, and 1.216017 mils per year. Corrosion rate increased as pH decreased, with Fe showing corrosion at pH 6.21, 5.18, 4.26, 3.85, and 3.22. The relationship between current density and corrosion rate was found to be proportional, with voltage values of 1.31, 2.24, 3.16, 5.11, and 7.1 amperes per square meter (A/m^2). This study confirms that inhibitor type, acidity (pH), and current density significantly influence corrosion behavior, where increasing pH and current density can accelerate corrosion, and potassium nitrate (KNO3) demonstrates superior corrosion inhibition compared to potassium chromate (K2CrO4).

Implementation Of Fuzzy Logic in The Dissolved Oxygen and pH Control System to Reduce the Risk of Death of Cyprinus Carpio Fish

Jinan Elvaretta Aqilah Setyabudi — 2025-09-02

Cultivation of Cyprinus carpio, commonly known as the goldfish, in aquariums requires strict monitoring of water quality to maintain the fish's health and ensure its survival. Key parameters such as dissolved oxygen and pH greatly affect the aquatic environment, where imbalances can lead to stress or death. This study aims to design and implement a dissolved oxygen and pH control system using fuzzy logic as an alternative to traditional PID-based or rule-based systems commonly used in aquaculture. The proposed system automatically detects water conditions (LOW, NORMAL, HIGH) and activates appropriate control responses. It integrates an SEN0237 dissolved oxygen sensor, an E-201C pH sensor, aerators, dosing pumps, and an Arduino-based microcontroller. Sensor data is processed via fuzzy inference to operate actuators—either to increase oxygen levels or inject buffer solutions for pH normalization. Unlike previous studies that focus on single-parameter control or fixed-response systems, this system offers a dual-parameter adaptive control approach. Experimental validation shows that the system maintains pH at 6–7 and DO at 3–4 mg/L, with sensor accuracy exceeding 95%. Over 10 days, fish survival improved in the controlled aquarium (7/10) compared to the uncontrolled aquarium (5/10). The system demonstrates potential to reduce water quality fluctuations, offering hope for a more stable aquaculture environment. This work contributes to the application of fuzzy logic in small-scale innovative aquaculture systems, highlighting its potential advantages over conventional methods.

Comparative Risk Prioritization in the Initiation Phase of the Pagerungan Besar Photovoltaic Plant: A Failure Mode and Effect Analysis (FMEA) and Risk Matrix Approach

Agustina Dwi Retnaningtias — 2025-09-02

Photovoltaic (PV) power plant projects in East Java often face challenges during the initiation phase due to inadequate risk assessments. This phase is crucial for ensuring the project's long-term success; however, suboptimal risk identification has caused project delays. In the risk assessment process, high-priority risks need to be mitigated, but differences in the methods used can result in varying risk priority outcomes. One of the methods that can be used is Failure Mode and Effect Analysis (FMEA), while according to internal regulations at PT PLN (Persero), the Risk Matrix is applied. By using these two methods, the differences in the resulting risk priority rankings can be identified. Both tools rely on evaluations from experts experienced in decision-making during the initiation phase of PV power plant projects. From the analysis, 12 risks were identified during the initiation phase of the Pagerungan Besar PV power plant project. The highest-priority risks identified include Suboptimal feasibility study (Risk Priority Number/RPN: 74.27), unfavorable outcomes for the organization/company (RPN: 68.96), lack of budget (RPN: 64.00), and stakeholder Intervention (RPN: 53.69). Meanwhile, by plotting the Severity Level and Occurrence Level of each risk on the Risk Matrix according to PT PLN (Persero) regulations, the highest-priority risks identified include Suboptimal feasibility study (Extreme Risk Level, Zone E5), location-related issues (Extreme Risk Level, Zone E5), non-compliance with regulations (Extreme Risk Level, Zone E5), and suboptimal project team (Very High Risk Level, Zone D5). The two risk assessment methods produced different prioritizations, potentially impacting mitigation strategy decisions. This variation highlights the need for further analysis to ensure accurate and reliable risk prioritization, which is critical for project success and efficient resource allocation. Future studies should focus on evaluating prioritization methods to support effective decision-making and ensure timely project implementation in line with the targeted Commercial Operation Date (COD).

Risk Evaluation Of The Shipyard Supply Chain Process On Ship Repair With The House Of Risk Matrix Method

Hanif Ardhio Firmansyah — 2025-09-02

One of the keys to the success of ship repair is the supply chain (SC) process of materials that arrive on time. However, delays in its implementation were still found due to poor SC risk management. The purpose of the study is to identify risk factors for SC delay, measure risk factors and evaluate risk factors. This study uses the HOR (House of Risk) method which identifies risk variables (risk events and risk agents) and designs mitigation actions. The results of the HOR phase 1 study show an assessment score in the form of Aggregate Risk potential (ARP) which has a high influence on KM repair. Lintas Damai 1 includes: Supplier's unpreparedness in fulfilling orders with a score of 225, the forwarder experienced a delay in scoring 116 and Needs rejuvenation of facilities and transportation with a score of 120 and KM. Shinpo19 includes the quality of materials from suppliers that are of poor quality with a score of 280, materials that are difficult to obtain in the area with a score of 138 and the layout of poorly organized storage warehouses with a score of 92. The results of HOR phase II include mitigation actions to handle risk agents in KM. Lintas Damai 1 includes finding trusted supplier partners, increasing networking with other suppliers, holding tenders with suppliers who are ready and conducting service and checks every month. Meanwhile, KM. Shinpo19 has mitigation actions to handle risk agents, namely replacing materials with the same specifications but still of quality, having supplier connections with quality standards, supervising suppliers so that they comply with quality standards and structuring materials based on their type.