Journal of Smart Science and Technology

Ultraviolet aging of polyethylene microbeads and cadmium (Cd2+) uptake in water: Surface morphology, kinetics, and isotherm analysis

2026-01-22T02:02:41+08:00

Polyethylene (PE) microbeads were subjected to three months of ultraviolet (UV) aging and evaluated for surface transformation and cadmium (Cd²⁺) uptake in aqueous solution. Scanning electron microscopy analysis showed that UV-aged microbeads developed pronounced surfaces, roughening with cracks and pit-like defects compared with virgin beads. This indicated an increased surface heterogeneity. Batch adsorption experiments (initial concentration, C₀= 0.2–1.0 mg L⁻¹) exhibited rapid Cd²⁺ uptake during the first few hours, followed by a slower approach to equilibrium at approximately 24–32 hours. Kinetic modelling showed that the pseudo-second-order (PSO) model better described the time-dependent data than the pseudo‑first-order (PFO) model (coefficient of determination,
R² ≈ 0.94–0.98 vs. 0.00–0.39), although model fits are treated as empirical descriptors rather than definitive evidence of a single adsorption mechanism. Equilibrium data were included using both Langmuir and Freundlich isotherms, which gave similarly good fits
(R² = 0.95 and 0.96, respectively) within the tested concentration range; therefore, no conclusive preference for one isotherm was asserted. The Langmuir maximum adsorption capacity (q_max = 0.0060 mg g⁻¹) was extremely low, indicating that UV-aged PE microbeads are not suitable as engineered sorbents for water treatment. Instead, their environmental relevance is better interpreted as auxiliary sorbent phases and mobile vectors that may contribute to Cd²⁺ redistribution in aquatic systems. This study supports SDG 14 by demonstrating that UV‑aged PE microbeads can adsorb and transport Cd²⁺, underscoring their role in spreading pollutants and threatening aquatic ecosystem health.

A 28-GHz hybrid corporate-series fed four-element patch antenna array with improved bandwidth for 5G millimetre wave application

2025-12-24T06:50:45+08:00

In this study, a different approach was taken toward the design and performance assessment of a four-element patch antenna operating at 28 GHz in the millimetre-wave band, specifically tailored for next‑generation 5G wireless communication applications. Implemented on a Rogers RT 5880 dielectric substrate known for its low loss characteristics, the antenna benefits from a substrate thickness of 0.5 mm and a relative dielectric constant (εᵣ) of 2.2. The antenna array employs a microstrip line feeding technique, ensuring efficient signal transmission and distribution across the elements. Evaluation of the single-element configuration at 28 GHz frequency reveals impressive characteristics, including a return loss of −26.3 dB, signifying excellent impedance matching. Additionally, the antenna achieves a gain of 7.75 dB, an outstanding Voltage Standing Wave Ratio (VSWR) of 1.10, and a bandwidth of 1.34 GHz. To further enhance these characteristics, the antenna was configured as a two-element and a four-element array. Compared with the single-element antenna, the two-element array at 28 GHz shows a greater gain of 9.88 dB and an improved bandwidth of 2.04 GHz, while the four-element array shows the greatest gain of 12.5 dB and an expanded bandwidth of 4.89 GHz at the intended frequency of 28 GHz. This demonstrates how antenna performance is enhanced by utilising array structures. The performance of the proposed antenna was validated through comparative analysis with similar 28 GHz array antenna designs. The results indicate that the proposed antenna outperforms existing designs in both gain and bandwidth. The proposed antenna enhances high-capacity 5G millimetre wave (mmWave) communication and supports digital infrastructure development in line with SDG 9: Industry, Innovation and Infrastructure.

Small-scale river flow hydropower: Design, IoT monitoring, and field validation

2025-09-26T07:46:31+08:00

Hydroelectric energy represents a sustainable and reliable power source for off-grid and remote areas, particularly in environments where conventional electricity access is limited and solar energy performance is reduced by dense vegetation. This study addresses the need for a portable, small-scale hydroelectric solution by developing and validating a lightweight IoT-enabled micro-hydroelectric generator designed to operate in low-head, densely vegetated stream environments. The proposed system integrates a compact micro-hydro turbine with an ESP32 microcontroller and a multi-sensor suite, including water flow, voltage, and current sensors, enabling real-time performance monitoring via the Blynk mobile platform. The novelty of this work lies in the integration of a fully portable form factor with IoT-based real-time monitoring, allowing rapid field deployment and performance evaluation without permanent infrastructure, which distinguishes it from conventional fixed micro-hydro systems. Field evaluation conducted over a 30-minute period indicates that the voltage and current generally increase with operating time, reaching peak values of 10.03 V and 22.29 mA at the 25-minute mark, corresponding to a maximum power output of 224 mW. The observed trends suggest stable energy generation under natural river flow conditions, with minor variations attributed to environmental factors such as flow fluctuations. Overall, the results demonstrate the practical feasibility of the proposed system as a portable off-grid energy solution for rural, outdoor, and emergency applications.

Rutting and fatigue cracking characteristics of toner-modified asphaltic blends

2025-04-16T07:24:55+08:00

The improper disposal of electronic waste, particularly waste toner cartridges, poses significant environmental challenges. This research investigated the application of waste toner powder, specifically the powder extracted from printer cartridges, as a modifier in asphaltic mixes to improve rheological characteristics, including fatigue cracking resistance and rutting resistance. Four (4) waste toners (A, B, C & D) were blended into Trinidad Lake Asphalt (TLA) and Trinidad Petroleum Bitumen (TPB) at concentrations of 0%, 5%, 10%, 15%, and 20%. The samples were analysed using dynamic shear rheology (DSR) testing to assess their mechanical properties. The results indicated that incorporating waste toner significantly improves asphalt's resistance to deformation and fatigue. The highest rutting resistance, G*/sin δ was observed in the 20% Toner B at 2.60 × 105 Pa, while the best fatigue cracking resistance, G*sin δ was found in 5% Toner D at 3.93 × 102 Pa. These findings suggest that waste toner-modified asphalt is a viable, sustainable alternative for road paving applications, contributing to both environmental conservation and infrastructure enhancement.

The impacts of the integration of onion biowaste and NPK fertiliser on okra productivity and economic profitability

2026-02-05T09:04:02+08:00

Inorganic fertilisers are effective for improving crop yields, but their overuse can lead to soil acidification, which degrades soil health and long-term plant growth. To address this issue, the integration of onion biowaste fertiliser with NPK fertiliser has been proposed as an environmentally sustainable alternative for okra cultivation. This study evaluates the influence of various combinations of onion biowaste and NPK fertilisers on the yield and economic performance of okra (Abelmoschus esculentus). The experiment was carried out under greenhouse conditions using a randomised complete block design (RCBD) consisting of five treatments with five replications each. The treatment levels were: T0 (control, 100% NPK fertiliser), T1 (100% onion biowaste fertiliser), T2 (50% NPK and 50% onion biowaste), T3 (30% NPK and 70% onion biowaste), and T4 (70% NPK and 30% onion biowaste). The results revealed significant differences in okra productivity and profitability across treatments. T2 (50% NPK fertiliser + 50% onion biowaste) was the most effective treatment that produced the highest fresh pods of 9250.25 kg per hectare with a gross profit margin of 62.80% and it was superior compared to all other treatment modes. Such a solution will offer the economy and the environment the best possible remedy to the fertiliser-related pollution, as well as transform household waste such as onions, into a valuable agricultural resource and a solution to the problem of fertilisers.

Liming and soil acidity management in tropical peatlands under oil palm: A review

2025-05-23T09:29:05+08:00

In Southeast Asia, vast tracts of tropical peatland have been converted to agricultural land, primarily for the establishment of oil palm plantations, due to anticipated significant economic benefits for the nations involved. Peat soils, on the other hand, have been considered a challenge for agricultural activities. One of the primary agronomic challenges in crop production on peat soil is its high acidity (pH 3.3–3.5) and low fertility. To address these constraints, liming has become a common agricultural practice to adjust soil pH. However, due to the substantial buffer capacity in peat soil, determining optimal lime rates for maximum productivity and cost-effectiveness is relatively challenging. Liming can enhance the physical, chemical, and biological characteristics of soil by reducing its acidity and mobilizing certain elements through direct and indirect mechanisms. Nevertheless, the effectiveness of lime in improving crop productivity is affected by various factors, including initial soil pH, peat heterogeneity, crop species, lime material type, and application method. Plants require a large amount of macronutrients to grow and thrive. In soil with high acidity, most macronutrients are less available to plants. Hence, this review aims to examine how liming helps manage soil acidity and improve soil conditions for oil palm growth on tropical peat soils.