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There has been a significant interest in the development of eco-friendly building materials. Recyclable and environmentally friendly, geopolymer composites are extraordinary binding materials. The purpose of this experimental study was to examine the mechanical and durability properties of metakaolin based self-compacting geopolymer concrete (SCGPC) comprising steel fibers (SF) and recycled aggregate concrete (RCA) varying percentages of recycled coarse aggregate. The mechanical and durability properties of the geopolymer composites, including fracturing tensile strength, and flexural strength, were subsequently evaluated. At weight proportions of 0%, 25%, 50%, 75% and 100%, the recycled coarse aggregates were substituted for the natural coarse aggregates. The amounts of SF incorporated into the mixtures were 0, 0.5, 1.0, and 1.5% by volume fraction. While the incorporation of SF does not yield a substantial improvement in compressive strength, it substantially enhances fracture tensile strength and flexural behavior. The load-displacement graph demonstrated that the incorporation of steel fibers into geopolymer composites increased their fracture toughness, resulting in a higher maximal load capacity. The findings suggest that the incorporation of RCA into SCGPC reduces its flexural behavior, splitting and compressive tensile strengths, and durability, particularly under peak load, deflection, and load. Furthermore, it is observed that RCA negatively synergize with respect to compressive and fracturing tensile strength. However, SF exhibit a significant positive synergy in terms of flexural properties. [ABSTRACT FROM AUTHOR]

This experimental study presents the effect of steel fiber (SF) and recycled coarse aggregate (RCA) on the fresh and hardened properties of Self-compacting geopolymer concrete (SCGC). Sixteenth alkali-activated based metakaolin (MK) concrete mixtures with constant binder content of 500 kg/m³ incorporated 0, 0.5, 1.0, and 1.5% volume fraction of SF and 0, 10, 20, and 30% RCA as a partially replacement for natural coarse aggregate (NCA) with sodium hydroxide concentration of 12 Molarity at ambient conditions. Fresh state of SCGC were examined slump flow, T500 flow, V-funnel, and L-box test. At 28 and 90 days the compressive strength and splitting tensile strength were investigated, the flexural strength was evaluated at 90 days. The results highlighted that RCA (30%) and SF (1.5%) significantly constrain the fresh properties of SCGC mixes. Moreover, SCGC incorporated RCA can be produced with compressive strength as high as 31.91-41.13 at 28 and 90 days, respectively. However, 1% SF and 30% RCA in MK-based SCGC appear better performance than the control mixture and leads to an ecologically friendly concrete mix that has appropriate hardening properties and that would contribute to the longevity of the construction industry. [ABSTRACT FROM AUTHOR]

The manufacture of cement plays a substantial role in the emission of carbon dioxide (CO2) into the atmosphere, hence exacerbating the adverse impacts of global warming. Consequently, the emergence of Geo-Polymer concrete has presented itself as a potentially feasible substitute owing to its commendable environmental sustainability. This manuscript provides a comprehensive analysis of prominent studies investigating the effects of increased temperatures and fire exposure on concrete across its entire operating duration. This study examines the significant impacts on the fundamental physical and mechanical characteristics of concrete, as revealed by laboratory experiments. Furthermore, this review comprehensively examines previous research endeavors that have used machine learning methodologies to predict tangible actions, aiming to optimize resource allocation, time efficiency, and cost-effectiveness in laboratory inquiries. Geo-Polymer concretes have exhibited remarkable resistance to elevated temperatures and severe fires, as evidenced by laboratory and field assessments of cracking, spalling, and strength degradation. Prior studies have demonstrated that both the aggregate type and temperature have a substantial impact on the degradation of compressive strength. Moreover, previous research has indicated that Geo-Polymeric concrete, which is comprised of fly ash, exhibits superior heat resistance compared to conventional concrete using Portland cement, withstanding temperatures of up to 400 degrees Celsius. This research also highlights the widespread adoption of the Artificial Neural Network (ANN) technique in forecasting the compressive strength of conventional concrete. Conversely, alternative approaches such as the Genetic Weighted Pyramid Operation Tree (GWPOT) are preferred for high-performance concrete. The primary objective of this extensive investigation is to establish a fundamental basis for future studies on sustainable alternatives to concrete and approaches for predictive modeling. [ABSTRACT FROM AUTHOR]

Predicting the compressive strength of concrete is a complicated process due to the heterogeneous mixture of concrete and high variable materials. Researchers have predicted the compressive strength of concrete for various mixes using machine learning and deep learning models. In this research, compressive strength of high-performance concrete with high volume ground granulated blast-furnace slag replacement is predicted using boosting machine learning (BML) algorithms, namely, Light Gradient Boosting Machine, CatBoost Regressor, Gradient Boosting Regressor (GBR), Adaboost Regressor, and Extreme Gradient Boosting. In these studies, the BML model's performance is evaluated based on prediction accuracy and prediction error rates, i.e., R2, MSE, RMSE, MAE, RMSLE, and MAPE. Additionally, the BML models were further optimised with Random Search algorithms and compared to BML models with default hyperparameters. Comparing all 5 BML models, the GBR model shows the highest prediction accuracy with R2 of 0.96 and lowest model error with MAE and RMSE of 2.73 and 3.40, respectively for test dataset. In conclusion, the GBR model are the best performing BML for predicting the compressive strength of concrete with the highest prediction accuracy, and lowest modelling error. [ABSTRACT FROM AUTHOR]

• The well-graded BA can be a good partial sand replacement material in concrete. • The compressive strengths for all mixes reached more than 50% on 28th curing days. • The split tensile strengths showed quadratic curve. • The slow growth of exponential pattern on flexural strengths was observed. • The compressive strength and thermal conductivity were highly correlated. Bottom ash (BA) is a hazardous waste material from power plant. The well-graded BA can be a good sand replacement material in concrete. This study presents strength and thermal properties of concrete containing high calcium and water absorptive fine aggregate from well-graded BA as partial sand replacement (control mix (CM) 0%, BM5: 5%, BM10: 10%, BM15: 15%, and BM20: 20%). The workability of fresh concrete mixes was tested via slump test. The strength of the hardened concrete was assessed based on compressive strength, split tensile strength, and flexural strength. The thermal property was evaluated based on thermal conductivity test. The optimization of these model parameters was conducted via I-Optimal design. The workability of concrete mixes was reduced with an increase of well-graded BA due to high water absorption effect. The compressive strengths of all mixes reached more than 50% on 28th curing days with maximum strength by BM15 (49.0 MPa). The split tensile strengths showed one quadratic curve combining all mixes with maximum strength reached by BM10 (2.7 MPa). The flexural strength has slow growth exponential pattern with maximum strength by BM20 (6.0 MPA). The thermal conductivity values were steadily increased up to BM15 (2.44 W/mK) and reduced at BM20 (2.15 W/mK). The well-graded BA proportions (5 to 20%) were not showing any significant effect on the thermal properties. The optimised model of compressive strength has the highest accuracy with percentage errors below 5% compared to other parameters. The optimal well-graded BA as sand replacement material was BM10 giving 47 MPa compressive strength, 2.7 MPa split tensile strength, 5.3 MPa flexural strength, and 2.1152 W/mK thermal conductivity. The highest positive correlation coefficients were obtained between compressive strength and thermal conductivity (R2: 0.921). Thus, the well-graded BA improved the strength properties providing a sustainable supply in concrete technology. [ABSTRACT FROM AUTHOR]

[Display omitted] • The physicochemical properties of hydrogel polymers in diapers were presented. • WDXRF, FTIR, XRD, pH, turbidity and colour were studied. • The chemical composition (chemical oxides) was determined. • The functional groups and chemical contents were identified. • The crystallinity, pH, turbidity and colour of ND and UD were described. Diapers are reusable waste. This research presents physicochemical properties of sodium polyacrylate in new (ND) and used (UD) diapers, via wavelength-dispersive X-ray fluorescence (WDXRF), Fourier transform infrared (FTIR), X-ray diffraction (XRD), pH, turbidity and colour. Additional constituents detected in ND, while others were slightly higher in UD. Slight decrease (2000–2500 cm−1, UD) and bulk peaks (3287–3333 cm−1, UD) were observed and functional group at 2897 cm−1 (ND) disappeared showing their role as absorption sites. The pH (6.83–8.50), turbidity (16.3–36.6 NTU) and colour (153–432 Pt.Co) values were obtained. Thus, this provides a baseline reference for diapers application in concrete technology. [ABSTRACT FROM AUTHOR]

Steep cut slops along the highways and hillsides closer development projects are generally stabilize using soil nailing method in Malaysia. Soil nail system (i.e., passive and active soil nail systems integrated with tendons pre-stressed) is widely applied to strengthened slopes. However, slope failures occurred observing flaws on the fundamental design. The loss of the pre-stressed tension on the creep behaviour of the nail tendon affects the functionality of the soil nail system. This research has introduced a cylindrical shape reinforced grout hybrid anchor and the objectives is to assess its efficiency at refraining the creep behaviour of the soil. Therefore, laboratory evaluation of the pull-out creep behaviour of the anchor was assessed in a large pull-out box (length: 2 m, σ: 1 m × 1 m). An effective stress of 100 and 200 kPa were applied to the soil in the pull-out box. The creep behaviour was tested at the pull-out tensions of 100 and 200 kN, respectively. Results show that the prestressing force is the main factor affecting the stress and deformation in the soil. The anchor was able to mobilise the tensions of 100 and 200 kN. The load was maintained, and the creep behaviour was monitored. A minimal amount of creep (approximately 1 mm) was observed. This finding presents a good justification showing that, the anchor could resist creep and thus can function as a maintenance free active soil nail system. [ABSTRACT FROM AUTHOR]

[Display omitted] • The physicochemical and leaching properties of FA and BA were presented. • BA and FA shown similar pozzolanic property, potential as alternative binder. • Heavy metals leaching of FA, BA and FA + BA were in permissible limits. • Pb is an indicator for existence of other heavy metals (i.e. Zn, Cu and As) Coal ash (fly (FA) and bottom (BA) ashes) contain heavy metals. This research presents physicochemical and leaching properties of coal ashes (FA, BA and FA + BA) from a Malaysian power plant. The physicochemical (X-ray fluorescence (XRF) and scanning electron microscopy (SEM)) and leaching properties (toxicity characteristic leaching (TCLP) and synthetic precipitation leaching (SPLP) procedures) of ash samples were determined. Heavy metals like lead (Pb), zinc (Zn), copper (Cu) and arsenic (As) were quantified using atomic absorption spectrometer (AAS). Leaching properties were found to complied to the standard guidelines for heavy metals. Further investigation on leaching properties is recommended for construction industry applications. [ABSTRACT FROM AUTHOR]

This review provides an intensive overview of flame retardant coating systems. The occurrence of flame due to thermal degradation of the polymer substrate as a result of overheating is one of the major concerns. Hence, coating is the best solution to this problem as it prevents the substrate from igniting the flame. In this review, the descriptions of several classifications of coating and their relation to thermal degradation and flammability were discussed. The details of flame retardants and flame retardant coatings in terms of principles, types, mechanisms, and properties were explained as well. This overview imparted the importance of intumescent flame retardant coatings in preventing the spread of flame via the formation of a multicellular charred layer. Thus, the intended intumescence can reduce the risk of flame from inherently flammable materials used to maintain a high standard of living. [ABSTRACT FROM AUTHOR]

It is obligatory to educate student researchers before they start their work by teaching them about the various types of plagiarism and how to avoid them. It is also vital that research supervisors take into account the sources of data that are explored in their students' manuscripts. This article tries to draw the reader's attention to the importance of avoiding all types of plagiarism in their research. [ABSTRACT FROM AUTHOR]

The potassium (K) and sodium (Na) elements in banana are needed for hydration reaction that can enhance the strength properties of concrete. This research aims (a) to determine the material engineering properties of banana skin ash (BSA) and concrete containing BSA, (b) to measure the strength enhancement of concrete due to BSA, and (c) to identify optimal application of BSA as supplementary cement materials (SCM) in concrete. The BSA characterization were assessed through X-ray fluorescence (XRF) and Blaine's air permeability. The workability, compressive strength, and microstructures of concrete containing BSA were analysed using slump test, universal testing machine (UTM) and scanning electron microscope (SEM). A total of 15 oxides and 19 non-oxides elements were identified in BSA with K (43.1%) the highest and Na was not detected. At 20 g of mass, the BSA had a higher bulk density (198.43 ± 0.00 cm3) than ordinary Portland cement (OPC) (36.32 ± 0.00 cm3) indicating availability of large surface area for water absorption. The concrete workability was reduced with the presence of BSA (0% BSA: > 100 mm, 1% BSA: 19 ± 1.0 mm, 2%: 15 ± 0.0 mm, 3% BSA: 10 ± 0.0 mm). The compressive strength increased with the number of curing days. The concrete microstructures were improved; interfacial transition zones (ITZ) decreased with an increase of BSA. The optimal percentage of BSA obtained was at 1.25%. The established model showed significant model terms (Sum of Squares = 260.60, F value = 69.84) with probability of 0.01% for the F-value to occur due to noise. The established model is useful for application in construction industries. [ABSTRACT FROM AUTHOR]

This study examines the results from an investigation on the impact resistance of oil palm shells (OPS) concrete. The use of OPS as a substitute for regular aggregate in lightweight concrete will help reduce its negative environmental influence. There is a lack of research on the impact resistance and crack behaviour of concrete; specifically in OPS lightweight concrete reinforced by polypropylene (PP) fibre. The replication of a low-velocity projectile effect on slab samples was achieved by dropping two types of steel ball (weighing 0.380 kg and 1.25 kg), with drop height of 360 mm, through the utilization of a self-fabricated drop-weight impact test rig. A total of 12 cube specimens, with dimensions 100 × 100 × 100 mm, were used to prepare 36 slabs with various thicknesses. The 36 slabs were prepared using a concrete cutting machine to excise the three cube specimens from each mixture, into 20, 30 and 40 mm thicknesses. Impact resistance tests were then performed on them. The results demonstrate that there was a strong linear relation between volume fraction of PP fibre and impact resistance; as well as crack resistance ratio. This relation was indefeasible by changing the thickness from 20 mm to 30 mm and 40 mm. Although increasing the thickness improved the impact resistance significantly, the effect was more pronounced for ultimate failure crack resistance than for first crack resistance. [ABSTRACT FROM AUTHOR]

This research explores the impact of earthquake directionality and orientation on the seismic performance of reinforced concrete (RC) frame structures, an area previously overlooked in seismic design. The multi-directional component of ground motion was not taken into consideration during the seismic performance design of the majority of RC frame structures. Focusing on a case study in Padang City, Indonesia, a region known for moderate seismic activity, this study assesses the behavior of an eight-story ordinary moment resisting frame (OMRF) under various directional components and orientation angles of ground motions. Through Nonlinear Dynamic Analysis (NL-DA) using Nonlinear Time History Analyses (NL-THA), the study incorporates 14 ground motions across East–West and North–South directions, varying from 0° to 60° in 15-degree increments. Incremental Dynamic Analysis (IDA) evaluates the building's response, employing capacity curves, fragility curves, and CMR scores to understand damage probabilities and structural behaviors under different earthquake directions. The objectives include (1) assessing the building's seismic resilience through IDA capacity curves in line with FEMA 356 performance-based design standards, (2) developing fragility curves and the CMR to predict the potential of damages and structural response in various ground motion directions, and (3) formulating a generic relationship between intensity measure (IM), structural behavior (SB), and incidence angle (θ) via regression analysis. Results highlight the crucial role of θ in influencing structural response, with deterioration in structural behavior noted as the angle of incidence increases. This pattern underscores the varying stress distributions and deformation patterns in response to directional ground movements. The study's findings emphasize incorporating directionality in seismic risk assessments and structural designs, offering valuable insights for improving resilience against future seismic events. Eventually, the link between θ, IM, and SB is crucial for assessing and mitigating seismic risk, since it indicates that θ is a major element impacting how buildings respond to seismic occurrences. [ABSTRACT FROM AUTHOR]

The usage of glass fiber reinforced polymer (GFRP) composite cross-arms in transmission towers is relatively new compared to wood timber cross-arms. In this case, many research works conducted experiments on composite cross-arms, either in coupon or full-scale size. However, none performed finite element (FE) analyses on full-scale composite cross-arms under actual working load and broken wire conditions. Thus, this work evaluates the performance of glass fiber reinforced polymer (GFRP) composite cross-arm tubes in 275 kV transmission towers using FE analysis. In this study, the performance analysis was run mimicking actual normal and broken wire conditions with five and three times more than working loads (WL). The full-scale assembly load test experiment outcomes were used to validate the FE analysis. Furthermore, the mechanical properties values of the GFRP composite were incorporated in simulation analysis based on the previous experimental work on coupons samples of GFRP tubes. Additionally, parametric studies were performed to determine the ultimate applied load and factor of safety for both normal and broken wire loading conditions. This research discovered that the GFRP composite cross-arm could withstand the applied load of five times and three times working load (WL) for normal and broken wire conditions, respectively. In addition, the factor of safety of tubes was 1.08 and 1.1 for normal and broken wire conditions, respectively, which can be considered safe to use. Hence, the composite cross-arms can sustain load two times more than the design requirement, which is two times the working load for normal conditions. In future studies, it is recommended to analyze the fatigue properties of the composite due to wind loading, which may induce failure in long-term service. [ABSTRACT FROM AUTHOR]

[Display omitted] • Rough set theory and PCA were applied for environmental data modelling. • The similarity assessment of 16 + 1 US EPA PAHs from Sungai Perak is presented. • LMW PAHs were found to be the most prominent in the water. • Variance were equal to 68.47% (Nap) and 27.63% (carbazole) • The LMW PAHs were likely due to incomplete combustion from vehicles. This paper presents application of rough set theory and PCA for modelling of similarity characteristics of PAHs from Perak River: Tanjung Belanja Bridge (TBB, l 1), Water Treatment Plant Parit (WTPP, l 2), Parit Town Discharge (PTD, l 3), Water Treatment Plant Senin (WTPS, l 4), and Water Treatment Plant Kepayang (WTPK, l 5). The clustering involved PAHs as attributes and sampling stations as objects. The l 1 and l 3 were clustered in Sim deg x , y ≥ 0.8. The Sim deg x , y ≥ 0.7 was observed in all attributes (except l 5) forming two sets of clusters. PCA showed that low molecular weight (LMW) PAHs were prominent with variances of 68.47% (naphthalene, Nap) and 27.63% (carbazole). [ABSTRACT FROM AUTHOR]

Abstract Polycyclic aromatic hydrocarbons (PAHs) are carcinogenic compounds, composed of benzene rings. The objective of this research was to identify the optimum condition for the degradation of PAHs contaminated water using photo-Fenton oxidation process via response surface methodology (RSM). Aqueous solution was prepared and potable water samples were collected from water treatment plants in Perak Tengah, Perak, Malaysia in September 2016. The reaction time, pH, molarity of H 2 O 2 and FeSO 4 were analyzed followed by RSM using aqueous solution. A five level central composite design with quadratic model was used to evaluate the effects and interactions of these parameters. The response variable was the percentage of total organic carbon (TOC) removal. PAHs quantification was done using gas chromatography mass spectrometry analysis. The regression line fitted well with the data with R 2 value of 0.9757. The lack of fit test gives the highest value of Sum of Squares (15,666.64) with probability F value 0.0001 showing significant quadratic model. The optimum conditions were established corresponding to the percentage of TOC removal. The PAHs removal efficiency for potable water samples ranged from 76.4% to 91% following the first order of kinetic rates with R 2 values of >0.95. Conventional water treatment techniques are not effective for PAHs removal. Thus, advanced oxidation processes may be considered as an alternative to conventional water treatment techniques in Malaysia and other developing countries. Graphical abstract Unlabelled Image Highlights • PAHs are carcinogenic compounds and abundantly found in mixed use area. • Perak River serves as principal water intakes in Perak Tengah, Perak, Malaysia. • Conventional water treatment techniques are inefficient for PAHs removal. • This research studies Photo-Fenton Oxidation Process for PAHs removal in water. • AOPs may be considered as an alternative to conventional water treatment. [ABSTRACT FROM AUTHOR]

• State-of-the-art and historical development of composite risers for deep waters. • Research findings on composite risers from detailed bibliographic review. • Overview on composite riser assessment based on structural and mechanical behaviour. • End-fitting designs, and stress profile from load responses on composite risers and end-fitting. • Marine industry application of marine riser configurations, like SLHR for composite risers. The need for the utilisation of marine risers in deep seas has increased in recent years and this is due to increased drilling explorations with the shift in trend from shallower to deep and deeper waters. Also, there have been increased applications in sea-crossing infrastructure resulting in the need for longer risers, leading to a significant weight increase of marine risers used. Composite materials can thus be utilised in marine riser engineering to provide lightweight, fatigue-resistant, corrosion-resistant, low-bending stiffness and high-strength characteristics. In this paper, the history and potential of composite marine risers, including the first successful deployment of a composite riser joint offshore on the Heidrun Platform in 1995, are reviewed. The paper also discusses the advances achieved on composite marine risers for deep waters and presents some recommendations on their use, in light of their current significance and growth. [ABSTRACT FROM AUTHOR]

The water stream has been reported to contain non-steroidal anti-inflammatory drugs (NSAIDs), released from households and premises through discharge from Sewage Treatment Plant (STP). This research identifies commonly consumed NSAIDs namely ibuprofen (IBU), diclofenac (DIC), ketoprofen (KET) and naproxen (NAP) in the influent wastewater from two urban catchments (i.e. 2 STPs). We expand our focus to assess the efficiency of monomer (C18) and dimer (HLB) types of sorbents in the solid phase extraction method followed by gas chromatography mass spectrometry (GCMS) analysis and optimize model prediction of NSAIDs in the influent wastewater using I-Optimal design. The ecological risk assessment of the NSAIDs was evaluated. The HLB produced reliable analysis for all NSAIDs under study (STP1: 6.7 × 10−3 mg L−1 to 2.21 × 10−1 mg L−1, STP2: 1.40 × 10−4 mg L−1 to 9.72 × 10−2 mg L−1). The C18 however, selective to NAP. Based on the Pearson proximity matrices, the DIC HLB can be a good indicator for IBU HLB (0.565), NAP C18 (0.721), NAP HLB (0.566), and KET HLB (0.747). The optimized model prediction for KET and NAP based on DIC are successfully validated. The risk quotients (RQ) values of NSAIDs were classified as high (RQ > 1), medium (RQ, 0.1–1) and low (RQ, 0.01–0.1) risks. The optimized models are beneficial for major NSAIDs (KET and NAP) monitoring in the influent wastewater of urban domestic area. An upgrade on the existing wastewater treatment infrastructure is recommended to counteract current water security situation. [Display omitted] • Influent wastewater of urban domestic area contains NSAIDs. • IBU, NAP, KET and DIC were analysed. • The efficiency of C18 and HLB sorbents were assessed. • The model parameters of NSAIDs in influent wastewater were modelled. • The estimated RQ values of NSAIDs were high, medium, and low risks. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAHs) are mutagenic and bio-accumulates in nature. This research aims to determine the ecological and health risk assessment of PAHs in Sungai Perak, Malaysia. The sampling was conducted at the up and downstream of Sungai Perak in the district of Perak Tengah, Malaysia. The sampling stations were Tanjung Belanja Bridge (TBB), Water Treatment Plant Parit (WTPP), Parit Town Discharge (PTD), Water Treatment Plant Senin (WTPS) and Water Treatment Plant Kepayang (WTPK). The water treatment plants channel water through the distribution network, to Manjung (249,600 people), Perak Tengah (249,600 people), Kinta (810,400 people) and Hilir Perak (144,400 people) districts. The hazard quotient (HQ) and hazard index (HI) were applied for ecological and health risk assessments. The lifetime cancer risk (LCR) was employed for the health risk assessment. The PAHs contamination level presumptions for all sampling campaigns were low (0–100 μg/L). The HI values of ecological and health risk assessments were found to be aligned with each other. The HI values for raw water were below one (<1) indicating low or no risk while the treated water HI values were more than one (>1) indicating to high risk to aquatic organisms and human health. However, the LCR for raw and treated water exceeded the maximum permissible limit, 1.0 × 10−6 equals to cancer risk of 1 in 1,000,000 people. The LCR for raw water were 1.71 × 10−4 (TBB), 1.35 × 10−4 (WTPP), 1.43 × 10−4 (PTD), 9.54 × 10−5 (WTPS) and 2.37 × 10−4 (WTPK). Meanwhile, the LCR for treated water were 6.90 × 10−5 (WTPP), 5.42 × 10−5 (WTPS) and 2.63 × 10−4 (WTPK). The conventional water treatment system appears to be inefficient to remove PAHs, risking the security of public health. Thus, restructuring the infrastructure of water treatment plants or considering an alternative to rivers as domestic water sources are highly recommended. [Display omitted] • Ecological and health risk assessments of PAHs in Sungai Perak were presented. • Sungai Perak posed low PAHs contamination level presumptions (0–100 μg/L). • Risk to aquatic organisms and human health: Raw (HI < 1) and treated (HI > 1) water. • The LCR for a population exceeded 1.0 × 10−6. • The conventional water treatment system is inefficient, risking the public health. [ABSTRACT FROM AUTHOR]

This research optimized the adsorption performance of rice husk char (RHC4) for copper (Cu(II)) from an aqueous solution. Various physicochemical analyses such as Fourier transform infrared spectroscopy (FTIR), field-emission scanning electron microscopy (FESEM), carbon, hydrogen, nitrogen, and sulfur (CHNS) analysis, Brunauer–Emmett–Teller (BET) surface area analysis, bulk density (g/mL), ash content (%), pH, and pHZPC were performed to determine the characteristics of RHC4. The effects of operating variables such as the influences of aqueous pH, contact time, Cu(II) concentration, and doses of RHC4 on adsorption were studied. The maximum adsorption was achieved at 120 min of contact time, pH 6, and at 8 g/L of RHC4 dose. The prediction of percentage Cu(II) adsorption was investigated via an artificial neural network (ANN). The Fletcher–Reeves conjugate gradient backpropagation (BP) algorithm was the best fit among all of the tested algorithms (mean squared error (MSE) of 3.84 and R2 of 0.989). The pseudo-second-order kinetic model fitted well with the experimental data, thus indicating chemical adsorption. The intraparticle analysis showed that the adsorption process proceeded by boundary layer adsorption initially and by intraparticle diffusion at the later stage. The Langmuir and Freundlich isotherm models interpreted well the adsorption capacity and intensity. The thermodynamic parameters indicated that the adsorption of Cu(II) by RHC4 was spontaneous. The RHC4 adsorption capacity is comparable to other agricultural material-based adsorbents, making RHC4 competent for Cu(II) removal from wastewater. [ABSTRACT FROM AUTHOR]