Hybrid polymeric membranes are often evaluated in terms of flux, rejection, and antifouling performance, whereas their adsorption kinetics and equilibrium behaviour are commonly treated as secondary considerations. This separation limits mechanistic understanding because dye removal by functional membranes is governed by the coupling between convective transport, pore-mediated retention, surface adsorption, filler dispersion and foulant-membrane interaction. This study aims to evaluate the kinetic and equilibrium behaviour of methylene blue (MB) adsorption by sequentially modified polyvinylidene fluoride (PVDF)-based hybrid membranes incorporating nanocellulose (NC), titanium dioxide (TiO2), graphene (GR) and graphene oxide-derived modified hybrid material (GO-mHM). Correspondingly, this study evaluates adsorption behaviour across the full sequence of membrane modification, enabling a comparative assessment of the contribution of each material component to adsorption kinetics and equilibrium performance, rather than limiting the analysis to the final optimised membrane formulation. Adsorption experiments were conducted at 25 °C using MB concentrations of 1-5 ppm, with adsorption capacity normalised to membrane area. The pseudo second order (PSO) model provided the most consistent kinetic fit with R 2 values generally ranging from 0.96 to 0.98. At 5 ppm MB, the equilibrium adsorption capacity increased from 1049.79 mg m-2 for pristine PVDF to 2080.69 mg m-2 for PVDF-4% NCM, followed by further improvement to 2408.14, 2442.68, and 2462.38 mg m-2 for PVDF/NC/3.0% TiO2, PVDF/NC/TiO2/0.2% GR, and PVDF/NC/TiO2/0.3% GO-mHM, respectively. Isotherm equilibrium modelling showed that the Freundlich model best described MB adsorption which indicates adsorption on a heterogeneous membrane surface with non-uniform adsorption sites. PVDF/NC/TiO2/0.3% GO-mHM exhibited the strongest adsorption response, recording a Freundlich K F of 75 501.71 mg m-2. These findings are consistent with MB adsorption occurring across chemically and structurally heterogeneous membrane domains, with filler composition, dispersion and interfacial accessibility influencing the observed adsorption response. The specific contributions of individual molecular interactions were not directly resolved and are therefore interpreted mechanistically rather than assigned as definitive adsorption pathways.
Sarawak coastal peatlands located on Borneo Island have vast availability of brackish peat water sources especially in some coastal rural areas. However, brackish peat water is currently underutilized as the source for water treatment plants due to excessive salinity levels. As such, this study aims to investigate the salinity reduction in brackish peat water sources for domestic consumption in Sarawak coastal peatlands by utilizing continuous electrocoagulation treatment with aluminium electrodes. Correspondingly, this study analyzes the effects of salinity percentage, electric current, and flow rate on salinity reduction with electrocoagulation treatment. This study has found that the treated salinity levels in brackish peat water with 30 % of salinity percentage meet the Malaysia Class I in National Water Quality Standard. The study has also identified both monolayer and multilayer adsorption that occurs in electrocoagulation treatment as the precursor to salinity reduction. In addition, the presence of in-situ aluminium hydroxide coagulants could adsorb some sodium chloride from brackish peat water with 70 % of salinity percentage at 2503 mg/g of maximum adsorption capacity and 2.65 min-1 of adsorption rate. This study has also found that electrocoagulation treatment could achieve 91.78 % of maximum salinity reduction efficiency at an optimum electric current of 5 A and flow rate of 1.2 L/min in brackish peat water with 30 % of salinity percentage. This treatment system costs only Ringgit Malaysia (RM) 0.29 or United States Dollars (USD) 0.06 per meter cubic of treated brackish peat water. Overall, this study demonstrates that continuous electrocoagulation treatment could partially desalinate brackish peat water with 30 % of salinity percentage in which the treated salinity levels could be utilized for domestic consumption in Sarawak coastal peatlands at reasonable cost.
The treatment of brackish peat water presents a formidable challenge due to its elevated levels of natural organic matter and salinity which not only hinder conventional water treatment systems but also necessitate an innovative approach to effectively manage these complex water characteristics. In response to these challenges, electrocoagulation has emerged as a promising alternative by utilizing electrochemical processes to efficiently destabilize and eliminate contaminants in brackish peat water sources. As such, this review aims to unveil challenges of aluminium electrodes fouling and passivation in electrocoagulation treatment system for sustainable water management of coastal Borneo peatlands. Several studies in the literature highlight that key operating parameters, especially electric current and voltage which play a pivotal role in influencing the overall effectiveness of these electrocoagulation systems. Although aluminium electrodes demonstrate high contaminants removal efficiencies, it remains susceptible to fouling and passivation due to contaminant buildup and oxide layer formation which increase electrical resistance and decrease electroactivity of redox reactions. The novelty of this review lies in its focused synthesis of fouling and passivation dynamics through the integration of Tafel plot analyses and advanced characterization techniques, particularly Energy Dispersive X-Ray (EDX) spectroscopy. Furthermore, a thorough understanding of the adsorption mechanisms, particularly through the interaction between aluminium hydroxides and contaminants is essential for enhancing system efficiency and mitigating fouling. Additionally, optimizing the electrocoagulation treatment system and conducting a detailed analysis of adsorption mechanisms, particularly through Tafel plot analysis are pivotal for enhancing the system efficiency. Advanced analytical methods such as Energy Dispersive X-Ray (EDX) spectroscopy provide deeper insights into floc composition that essential for improving contaminants removal strategies. Overall, this review offers a focused assessment on the interplay between brackish peat water and electrocoagulation in order to provide a foundation for future research aimed at developing sustainable treatment systems for coastal Borneo peatlands.