The development of sustainable hydrogels from renewable biomass has attracted increasing interest for environmental and agricultural applications. In this study, cellulose isolated from Pandanus tectorius leaves was utilized as a precursor for the synthesis of carboxymethyl cellulose (CMC), which was subsequently used to prepare hydrogels through ester-based crosslinking. A dual-network hydrogel structure was formed by blending CMC with hydroxyethyl cellulose (HEC), followed by esterification with citric (CA), fumaric (FA), and malic (MA) acids. Structural characterization using FTIR confirmed successful carboxymethylation and ester crosslinking within the polymer network, while SEM revealed a porous morphology favorable for water diffusion. The synthesized hydrogels exhibited gel fractions of 67–89%, swelling ratios of 578–4163%, and maximum degradation temperatures of 311–428°C. The CMC/HEC-MA hydrogel at a 15% crosslinker concentration demonstrated the most balanced combination of swelling capacity, gel fraction, and thermal stability. Owing to their high water-retention capability, porous structure, and biodegradability, these hydrogels show strong potential as superabsorbent materials for soil moisture conservation, controlled water release in agriculture, drought mitigation, and sustainable water management. These findings highlight the potential of biomass-derived hydrogels to support SDG 2 (Zero Hunger) by improving agricultural water retention, SDG 6 (Clean Water and Sanitation) by promoting efficient water management and treatment, and SDG 12 (Responsible Consumption and Production) by transforming renewable biomass resources into sustainable value-added materials.
The U-6Zr alloys, considered as nuclear fuel, must endure mechanical, thermal, and corrosive loads. Corrosion resistance is crucial during reactor operation and storage, as environmental conditions can trigger material degradation. Niobium (Nb) addition is expected to suppress corrosion. The U-6Zr-xNb alloys (x = 0, 1, 4, and 7 wt.%) were fabricated using arc melting and tested in acidic and alkaline environments. XRD analyses before corrosion revealed that the x = 0 and 1 wt.% alloys consisted of a single α-U phase, while the x = 4 wt.% alloy showed both α-U and γ-U phases. At x = 7 wt.%, only the α-U phase was present. After corrosion, XRD showed the formation of α-U and UO₂ phases for x = 0 and 1 wt.%, α-U, γ-U, and UO₂ phases for x = 4 wt.%, and only the α-U phase for x = 7 wt.%. Electrochemical tests demonstrated that E_corr increased and the corrosion rate (CR) decreased with increasing Nb content. Thus, Nb effectively enhanced the corrosion resistance of the U-6Zr alloys. Among all compositions, the U-6Zr-7Nb alloy showed the lowest corrosion rate and highest corrosion resistance in both environments, suggesting its strong potential as a nuclear fuel candidate.
Jacobson-type graphs provide a combinatorial framework for studying structural properties of finite commutative rings. We address two foundational questions: the behavior of these graphs under subring inclusions, and conditions under which distinct Jacobson-type constructions are isomorphic. This paper proves that whenever S is a subring of a finite commutative ring R, the Jacobson-type graphs of S arise naturally as induced subgraphs of the corresponding graphs of R, with finiteness playing an essential role in sustaining this embedding. We further characterize precisely when the Jacobson graph, the nn-array Jacobson graph, and the matrix Jacobson graph over a ring are isomorphic. These results establish a correspondence between algebraic relations of rings and combinatorial relations of their associated graphs.
The development of efficient and recyclable photocatalysts offers promising alternatives for wastewater treatment. However, significant challenges remain, including inefficient light utilization for photodegradation and rapid charge-carrier recombination. This study aims to synthesize a distinctive reusable BiVO4/Fe3O4/g-C3N4 (BNFC) photocatalyst with magnetic recovery via a one-pot hydrothermal method for visible-light methylene blue (MB) degradation. The optimal composite, BNFC-0.5, exhibited superior photocatalytic performance, achieving a degradation efficiency of 93.04% under optimal conditions of catalyst composition, pH 9, and 160 minutes of irradiation, with a TOC mineralization efficiency of 42.48%. The high degradation efficiency of the BNFC-0.5 composite is ascribed to its enhanced ability to harvest visible light, facilitate electron excitation with lower energy input, and promote effective electron–hole migration via the proposed Z-scheme configuration. Evaluation of the reactive oxygen species revealed that hydroxyl radicals (•OH) made the greatest contribution to the oxidation of MB. Kinetic assessment of the photocatalytic process revealed that the experimental behavior was adequately described by the Langmuir–Hinshelwood model, indicating a pseudo-first-order degradation pathway. In addition, the photocatalyst maintained a degradation efficiency of 79.32% over four cycles, demonstrating good stability and reusability, which is supported by the composite’s good structural stability. Overall, the findings demonstrate that constructing a ternary heterojunction is an effective strategy for enhancing the composite’s photocatalytic capability. Owing to its high degradation efficiency and reusability, the composite represents a promising candidate for wastewater purification under visible-light conditions.
The effects of the two biggest storms of Solar Cycle 25, the intense geomagnetic storms of May 10–11 and October 10–11, 2024, on the Indonesian equatorial region are examined in this study. For the 500-kV Jawa-Madura-Bali (JAMALI) transmission network, geomagnetically induced current (GIC) modeling was integrated with magnetometer and ionosonde observations from Pontianak (PTN), close to the geomagnetic equator, and Kupang (KPG), close to the southern crest of the Equatorial Ionization Anomaly (EIA). During both storms, significant equatorial amplification was noted. While the October storm caused lower local perturbations, the horizontal magnetic disturbance at PTN during the May event reached -471 nT, around 16% bigger than the minimum global Dst index (-406 nT). In the JAMALI network, rapid changes in the geomagnetic field produced geoelectric fields that caused quasi-DC currents of 0.6–1.6 A. Such currents may contribute to long-term transformer stress even when they are below essential operational criteria. Significant ionospheric disruptions were caused by both storms, with foF2 reductions of more than 50% and matching drops in maximum usable frequency (MUF) of about 4 MHz, suggesting increased dangers to HF communication equipment. Ionospheric variability over Indonesia is regulated by geomagnetic latitude, local time, storm-time electrodynamic forcing, and thermospheric dynamics, as demonstrated by the differences between PTN and KPG responses.
