A new effective adsorbent, 3-aminopropyltrimethoxysilane functionalized magnetic sporopollenin (MSp@SiO2NH2) based silica-coated graphene oxide (GO), (GO@SiO2-MSp@SiO2NH2) was successfully synthesized and applied for the first time in the removal of hazardous Pb(II) ions from aqueous solution. The properties of the composite were characterized using Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX) and vibrating-sample magnetometery (VSM). Evaluation of GO@SiO2-MSp@SiO2NH2 adsorption performance at optimum conditions revealed that the adsorbent has a maximum adsorption capacity of 323.5 mg/g for Pb(II) using 50-200 mg/L initial Pb(II) ions concentrations. Initial and final concentrations of Pb(II) ions in aqueous solution were analyzed using graphite furnace atomic absorption spectroscopy (GF-ASS). The adsorption behavior of Pb(II) ions onto GO@SiO2-MSp@SiO2NH2 was studied using Langmuir, Freundlich and Temkin isotherms models. The values of coefficient of determination showed that the adsorption best fitted the Langmuir model (R2 = 0.9994). Kinetic studies suggested that the adsorption of Pb(II) ion followed a pseudo-second-order rate model (R2 = 1.00) and thermodynamic studies revealed that the adsorption process is endothermic and spontaneous. The effect of co-existing ions on Pb(II) ion adsorption were also studied and found to have considerable effects only at higher matrix concentration. The adsorbent can be reused up to ten times and retain its good adsorption capacity. In addition, GO@SiO2-MSp@SiO2NH2 showed great potential for Pb(II)removal from industrial wastewater samples.
In light of concerns relating to improper waste disposal and resources preservation, reclamation of the discarded glass in construction materials had been extensively carried out since 1963. In the past decade, although more than 100 papers associated with the use of glass powder (GP) in the micron level scale were published, comprehensive review of all practical applications in cement-based materials and construction products is not available. This paper therefore provides a summary of the body of knowledge on the interaction and effects of using GP in cement-based and extended construction materials. This review concludes that GP is an innovative and promising eco-supplementary cementitious material. Beyond that, use of GP is demonstrated to be potentially beneficial as a precursor in geopolymer and suitable for manufacturing eco-cement, artificial lightweight aggregate and composite phase change material. The multiple applications of GP are seen as an important step towards waste glass recycling as a sustainable construction material and for the overall betterment of the industry.
Production of cellulases and xylanase by a novel Trichoderma asperellum UC1 (GenBank accession no. MF774876) under solid state fermentation (SSF) of raw oil palm frond leaves (OPFL) was optimized. Under optimum fermentation parameters (30 °C, 60-80% moisture content, 2.5 × 106 spores/g inoculum size) maximum CMCase, FPase, β-glucosidase and xylanase activity were recorded at 136.16 IU/g, 26.03 U/g, 130.09 IU/g and 255.01 U/g, respectively. Cellulases and xylanase were produced between a broad pH range of pH 6.0-12.0. The enzyme complex that comprised of four endo-β-1,4-xylanases and endoglucanases, alongside exoglucanase and β-glucosidase showed thermophilic and acidophilic characteristics at 50-60 °C and pH 3.0-4.0, respectively. Glucose (16.87 mg/g) and fructose (18.09 mg/g) were among the dominant sugar products from the in situ hydrolysis of OPFL, aside from cellobiose (105.92 mg/g) and xylose (1.08 mg/g). Thermal and pH stability tests revealed that enzymes CMCase, FPase, β-glucosidase and xylanase retained 50% residual activities for up to 15.18, 4.06, 17.47 and 15.16 h of incubation at 60 °C, as well as 64.59, 25.14, 68.59 and 19.20 h at pH 4.0, respectively. Based on the findings, it appeared that the unique polymeric structure of raw OPFL favored cellulases and xylanase productions.
Photocatalytic degradation is among the promising technology for removal of various dyes and organic contaminants from environment owing to its excellent catalytic activity, low energy utilization, and low cost. As one of potential photocatalysts, Fe2O3 has emerged as an important material for degradation of numerous dyes and organic contaminants caused by its tolerable band gap, wide harvesting of visible light, good stability and recyclability. The present review thoroughly summarized the classification, synthesis route of Fe2O3 with different morphologies, and several modifications of Fe2O3 for improved photocatalytic performance. These include the incorporation with supporting materials, formation of heterojunction with other semiconductor photocatalysts, as well as the fabrication of Z-scheme. Explicitly, the other photocatalytic applications of Fe2O3, including for removal of heavy metals, reduction of CO2, evolution of H2, and N2 fixation are also deliberately discussed to further highlight the huge potential of this catalyst. Moreover, the prospects and future challenges are also comprised to expose the unscrutinized criteria of Fe2O3 photocatalyst. This review aims to contribute a knowledge transfer for providing more information on the potential of Fe2O3 photocatalyst. In the meantime, it might give an idea for utilization of this photocatalyst in other environmental remediation application.
The disposal of oil palm biomass is a huge challenge in Malaysian oil palm plantations. The aim of this study was to develop efficient solid-state cultivated (SSC) ligno-hemicellulolytic bio-degrader formulations of indigenous white-rot hymenomycetes (Trametes lactinea FBW and Pycnoporus sanguineus FBR) utilizing oil palm empty fruit bunches (EFB), rubber wood sawdust (SD) and vermiculite (V) either alone or in combination as substrates. Based on significant laccase (849.40 U mg-1 protein), xylanase (42.26 U g-1 protein) and amylase (157.49 U g-1 protein) production, SD+V (T5) and V (T3) were the optimum substrates for SSC of T. lactinea FBW. Whereas, utilizing EFB (T1) substrate for SSC of P. sanguineus FBR enhanced the production of MnP (42.51 U mg-1 protein), LiP (103.20 U mg-1 protein) and CMCase (34.39 U g-1 protein), enzymes. Apparently, this is the first study reporting on the protein profiles by T. lactinea FBW, producing two isoforms of un-purified laccase (~55 and 70 kDa) and MnP (~40 and 60 kDa) and a CMCase band (~60 kDa) during SSC on SD+V (T5) substrate. Interestingly, this is also the first report to document a single isoform of un-purified laccase (~50 kDa), MnP (~45 kDa), CMCase (~60 kDa) and xylanase (~55 kDa) by P. sanguineus FBR during SSC on empty fruit bunches substrate. The computed Principal Component Analysis (PCA) Biplot analysis elucidated the relationship between the solid substrate compositions, the hymenomycete strain, ligno-hemicellulolytic enzyme profiles, and cultivation time. Therefore, it is suggested to use PCA as a tool for multivariate analysis method for comprehensive selection and optimization of ligno-hemicellulolytic enzyme cocktails by the indigenous white rot hymenomycetes. These non-toxic (acute oral toxicity) formulations are safe to be used in field applications to efficiently degrade oil palm trunks and root mass that had been felled, chipped or pulverized under zero burning waste management program. This study could also serve as an alternative method for efficient utilization of agro-industrial waste as substrates for the development of cost-effective bio-degraders formulations for agro-waste management.
This review intends to integrate the relevant information that is related to pesticide applications in food commodities and will cover three main sections. The first section encompasses some of the guidelines that have been implemented on management of pesticide application worldwide, such as the establishment of a value called Maximum Residue Level (MRL) through the application of Good Agricultural Practices (GAPs) into daily agricultural activities. A brief overview of the methods adopted in quantification of these trace residues in different food samples will also be covered. Briefly, pesticide analysis is usually performed in two stages: sample preparation and analytical instrumentation. Some of the preparation methods such as QuEChERs still remain as the technique of choice for most of the analytical scientists. In terms of the instrumentation such as the gas chromatography-mass spectrophotometry (GC-MS) and high performance-liquid chromatography (HPLC), these are still widely used, in spite of new inventions that are more sustainable and efficient such as the capillary electrophoresis (CE). Finally, the third section emphasizes on how pesticides can affect our health significantly whereby different types of pesticides result in different adverse health implications, despite its application benefits in agriculture in controlling pests. To date, there are limited reviews on pesticide usage in many agricultural-based nations; for the purpose of this review, Malaysia is selected to better illustrate pesticide regulations and implementation of policies. Finally, the review aims to provide an insight on how implementation of GAP and food safety assurance are inter-related and with this established correlation, to identify further measures for improvement to enable reinforcement of optimised agricultural practices specifically in these countries.
This study critically reviews the recent developments and future opportunities pertinent to the conversion of CO2 as a potent greenhouse gas (GHG) to fuels and valuable products. CO2 emissions have reached an alarming level of around 410 ppm and have become the primary driver of global warming and climate change leading to devastating events such as droughts, hurricanes, torrential rains, floods, tornados and wildfires across the world. These events are responsible for thousands of deaths and have adversely affected the economic development of many countries, loss of billions of dollars, across the globe. One of the promising choices to tackle this issue is carbon sequestration by pre- and post-combustion processes and oxyfuel combustion. The captured CO2 can be converted into fuels and valuable products, including methanol, dimethyl ether (DME), and methane (CH4). The efficient use of the sequestered CO2 for the desalinization might be critical in overcoming water scarcity and energy issues in developing countries. Using the sequestered CO2 to produce algae in combination with wastewater, and producing biofuels is among the promising strategies. Many methods, like direct combustion, fermentation, transesterification, pyrolysis, anaerobic digestion (AD), and gasification, can be used for the conversion of algae into biofuel. Direct air capturing (DAC) is another productive technique for absorbing CO2 from the atmosphere and converting it into various useful energy resources like CH4. These methods can effectively tackle the issues of climate change, water security, and energy crises. However, future research is required to make these conversion methods cost-effective and commercially applicable.
This study was conducted to examine the production of bioflocculants using agricultural wastewater as a fermentation feedstock under different temperatures and incubation times. The mechanism of flocculation was studied to gain a detailed understanding of the flocculation activity. The highest bioflocculant yield (2.03 g/L) at a temperature of 40 °C was produced in a palm oil mill effluent medium (BioF-POME). Bioflocculant produced from a fermented SME medium (BioF-SME) showed the highest activity. The flocculation tests for colour and turbidity removal from lake water indicated that BioF-SME and BioF-POME performed comparably to commercial alum. Analyses of the bioflocculants using liquid chromatography-mass spectrometry (LC-MS) found that the bioflocculants contained xylose and glucose. The mechanism study showed that flocculation occurred through charge neutralization and interparticle bridging between the bioflocculant polymer and the particles in the lake water. Thus, agricultural wastewater can be used as a fermentation feedstock for high-quality bioflocculants.
An alternative method was proposed to optimize the treatment process of palm oil mill effluent (POME) in an effort to address the poor removal efficiencies in terms of the chemical and biological oxygen demand (COD and BOD), total suspended solids (TSS) as well as oil and grease (O&G) content in treated POME along with many environmental issues associated with the existing POME treatment process. The elimination of the cooling ponds and the insertion of a dewatering device in the treatment process were recommended. The dewatering device should enhance the anaerobic digestion process by conferring a means of control on the digesters' load. The objective of this study is to identify the optimum solid: liquid ratio (total solids (TS) content) that would generate the maximum amount of biogas with better methane purity consistently throughout the anaerobic digestion of POME, all while improving the treated effluent quality. It was established that a 40S:60L (4.02% TS) was the best performing solid loading in terms of biogas production and methane yield as well as COD, BOD, TSS, and O&G removal efficiencies. Meanwhile, at higher solid loadings, the biogas production is inhibited due to poor transport and mass transfer. It is also speculated that sulfate-reducing bacteria tended to inhibit the biogas production based on the significantly elevated H2S concentration recorded for the 75S:25L and the 100S loadings.
Growing concerns of water pollution by dye pollutants from the textile industry has led to vast research interest to find green solutions to address this issue. In recent years, heterogeneous photocatalysis has harvested tremendous attention from researchers due to its powerful potential applications in tackling many important energy and environmental challenges at a global level. To fully utilise the broad spectrum of solar energy has been a common aim in the photocatalyst industry. This study focuses on the development of an efficient, highly thermal and chemical stable, environmentally friendly and metal-free graphitic carbon nitride (g-C3N4) to overcome the problem of fast charge recombination which hinders photocatalytic performances. Nitrogen-doped carbon quantum dots (NCQDs) known for its high electronic and optical functionality properties is believed to achieve photocatalytic enhancement by efficient charge separation through forming heterogeneous interfaces. Hence, the current work focuses on the hybridisation of NCQDs and g-C3N4 to produce a composite photocatalyst for methylene blue (MB) degradation under LED light irradiation. The optimal hybridisation method and the mass loading required for maximum attainable MB degradation were systematically investigated. The optimum photocatalyst, 1 wt% NCQD/g-C3N4 composite was shown to exhibit a 2.6-fold increase in photocatalytic activity over bare g-C3N4. Moreover, the optimum sample displayed excellent stability and durability after three consecutive degradation cycles, retaining 91.2% of its original efficiency. Scavenging tests were also performed where reactive species, photon-hole (h+) was identified as the primary active species initiating the pollutant degradation mechanism. The findings of this study successfully shed light on the hybridisation methods of NCQDs which improve existing g-C3N4 photocatalyst systems for environmental remediation by utilising solar energy.
In this work, the influence of pyrolysis temperature on the physicochemical properties of palm oil mill sludge biochar (POSB) and its adsorption properties towards cadmium (Cd) and copper (Cu) was investigated. Characterization experiments suggested that POSBs' surface functional groups play the major role in the adsorption process. POSB pyrolyzed at 400 °C showed the best characteristics for Cu and Cd removal. Adsorption study indicated that contact time and shaking speed enhances the adsorption capacity of POSB. It was affirmed that pH adjustment is not necessary for POSB to adsorb Cu and Cd. Mechanism studies fitted well with Langmuir and Pseudo-Second Order model. Thermodynamic parameters indicated that the adsorption was spontaneous, endothermic and correspond to chemical adsorption. The highest uptakes of Cu and Cd were recorded at 48.8 mg/g and 46.2 mg/g respectively. This work verifies that the temperature used for palm oil mill sludge (POS) pyrolysis and adsorption condition played the most prominent role in Cu and Cd removal from aqueous solutions.
In this study two deep eutectic solvents (DESs) were prepared using ethylene glycol (EG) and two different ammonium-based salts. The potential of these DESs as novel agents for CNTs functionalization was examined by performing a comprehensive characterization study to identify the changes developing after the functionalization process. The impact of DESs was obvious by increasing the surface area of CNTs to reach 197.8 (m2/g), and by adding new functional groups to CNTs surface without causing any damage to the unique structure of CNTs. Moreover, CNTs functionalized with DESs were applied as new adsorbents for the removal of methyl orange (MO) from water. The adsorption conditions were optimized using RSM-CCD experimental design. The kinetics and the equilibrium adsorption data were analyzed using different kinetic and isotherm models. According to the regression results, adsorption kinetics data were well described by pseudo-second order model, whereas adsorption isotherm data were best represented by Langmuir isotherm model. The highest recorded maximum adsorption capacity (qmax) value was found to be 310.2 mg/g.
After twenty-four years of government efforts, the latest national recycling rate in Malaysia rose from 5% in 1993 to approximately 24.6% in 2017. However, the practice of solid waste recycling in developing countries is still challenging compared to developing countries. Especially in Malaysia, a multi-ethnic country where people with different ethics have different living lifestyles. Still, Malaysia faces rapidly increasing solid waste and management costs, lacks appropriate data on solid waste management and recycling, lacks awareness of the 3R's (reduce, reuse and recycle) culture and lacks policies to promote 3R's culture. In addition, prior to the enforcement of ACT 672, information and networks between stakeholders have been limited for more than 20 years. Some scholars believe that the success of recycling practices is mainly influenced by community recycling behaviours. Therefore, in order to improve and evaluate the effectiveness of current national solid waste recycling management systems, research and assessment of community recycling behaviours are essential. This paper aims to evaluate the factors that attract communities to implement recycling in their daily lives and to obtain data through quantitative survey methods. Face-to-face questionnaires are conducted through purposive sampling and collected data is further analysed by PASW statistical tools. The comparison between recyclers and non-recyclers are presented in terms of frequency, means scores and radar chart. The results indicate that policy makers involved in the planning, organisation, and implementation of community recycling programs have to focus on strategies that engage community members and adopt recycling practices to improve environmental impact by changing their attitudes. Based on the results of means scores, the type of age, occupation and place of life must be taken into consideration in order to organize future recycling campaigns or awareness programs. In conclusion, the information will help policymakers make better solid waste recycling management to meet the needs of the public.
Microwave-steam activation (MSA), an innovative pyrolysis approach combining the use of microwave heating and steam activation, was investigated for its potential production of high grade activated carbon (AC) from waste palm shell (WPS) for methylene blue removal. MSA was performed via pyrolytic carbonization of WPS to produce biochar as the first step followed by steam activation of the biochar using microwave heating to form AC. Optimum yield and adsorption efficiency of methylene blue were obtained using response surface methodology involving several key process parameters. The resulting AC was characterized for its porous characteristics, surface morphology, proximate analysis and elemental compositions. MSA provided a high activation temperature above 500 °C with short process time of 15 min and rapid heating rate (≤150 °C/min). The results from optimization showed that one gram of AC produced from steam activation under 10 min of microwave heating at 550 °C can remove up to 38.5 mg of methylene blue. The AC showed a high and uniform surface porosity consisting high fixed carbon (73 wt%), micropore and BET surface area of 763.1 and 570.8 m2/g respectively, hence suggesting the great potential of MSA as a promising approach to produce high grade adsorbent for dye removal.
Inaccessible hygiene water sources and sanitation are one of the sustainability issues that need to be solved. An attempt to solve this problem is to change the conventional system used in the water supply and sewage treatment to sustainable water and waste management. To transform the system, companies initially need to map their business value chain. However, this process is often not receiving a full attention by the organisation. In an academic perspective, there are limited studies that map the value chains of water and waste systems. To overcome this limitation, the present study aims to map the value chain processes of the water and wastewater utility companies towards a sustainability solution. A review of related studies is used to conduct this study. Khuzestan Urban Water and Sewage company in Iran has been selected as case studies. The mapping results indicate a lack of sustainability integration in a water management system that leads to ineffective and inefficient water management. Value chain mapping process is significant for practitioners, particularly in the water and sewage companies, as a starting point for transforming their conventional water management systems towards sustainability. Experts at the company stated that value chain mapping as part of value chain analysis enables organisations to increase operational efficiency and eliminate waste by 57%.
Studies on sustainable management of waste from electrical and electronic equipment (or e-waste) have gained increasing attention from researchers around the world in recent years, with investigations into various aspects of e-waste management were investigated. Studies on e-waste generation by previous papers have been reviewed to provide an overview of the current research progress and recommendations for future research. The relevant existing studies were collected from various databases. Using content analysis, three main aspects of the existing studies were evaluated: the distribution and trends of the publications, the scope and boundaries of the studies, and the current research practices and research applications. Although there was a significant increasing trend of the amount of research on the evaluation of e-waste generation, however, the number of publications based on the countries of origin was still small. Another limitation was found related to the differences in the selection of research subjects and the level of analysis resulted in variations in the scopes and boundaries of the existing studies. Various other research areas were investigated further based on their research findings, but the analysis of various methodological aspects was complicated due to the increasing number of newly developed methodologies and the lack of comprehensive and up-to-date reviews on this research area. Additionally, there was also a need to evaluate emerging and/or older technology, which led electrical appliances to be overlooked. We found that comprehensive and up-to-date reviews of the methodological aspects of e-waste generation are still lacking. Based on the research gaps and limitations discussed, recommendations for future research were made.
Surfactants are the emerging contaminant and cause a detrimental effect on the ecosystem. In this study, an attempt is made to removal anionic surfactant Sodium dodecyl sulfate (SDS) containing wastewater using hydrophilic polyvinylpyrollidone (PVP) (5-15 wt%) modified polyethersulfone (PES) ultrafiltration membrane. The influence of operating variables on membrane performance was also sequentially analyzed using tests and three numerical modeling methods such as multiple linear regression (MLR), multiple Ln-equation regression (MLnER), and gene expression programming (GEP). Contact angle value of 10 wt% PVP modified PES membrane decreased up to 23.8°, whereas the neat PES membrane is 70.7°. This study indicates that the required hydrophilic property was improved in the modified membrane. The water flux and porosity also enhanced in PVP modified PES membranes. In performance evaluation, the optimum operating variable condition of transmembrane pressure (TMP), feed concentration, and the temperature is found to be 3 bar, 100 ppm, and 25 °C, respectively. Among the models, GEP has a good correlation with experimental anionic surfactant SDS filtration data. GEP performs better than other model with respect to statistical parameter and error terms. This study provides an insight into an adaptation of novel numerical modeling methods for the prediction of membrane performance to the treatment of surfactant wastewater.
Intensity-duration-frequency (IDF) curves can serve as useful tools in risk assessment of extreme environmental events. Thus, this study proposes an IDF approach for evaluating the risk of expected occurrences of extreme air pollution as measured by an air pollution index (API). Hourly data of Klang city in Malaysia from 1997 to 2016 are analyzed. For each year, a block maxima size is determined based on four different monsoon seasons. Generalized extreme value (GEV) distribution is used as a model to represent the probabilistic behavior of maximum intensity of the API, which is derived from each block. Based on the GEV model, the IDF curves are developed to estimate the extreme pollution intensities that correspond to various duration hours and return periods. Considering the IDF curves, we found that for any duration hour, the magnitude of pollution intensity tends to be high in parallel with increasing return periods. In fact, a high-intensity pollution event that poses a high risk of affecting the environment is less frequent than low-intensity pollution. In conclusion, the IDF curves provide a good basis for decision makers to assess the expected risk of extreme pollution events in the future.
Waste prevention and management become a significant issue worldwide to achieve sustainable development. Similar to many developing countries, Malaysia has faced severe problems in waste management due to its rapid economic growth and urbanisation. The municipal solid waste (MSW) production rate in Malaysia had increased significantly in a recent year, ranging from 0.8 to 1.25 kg/person∙d. The wastes generated contain a high amount of organic portion with high moisture content. Improper MSW management practice or delayed in waste collection and transportation can lead to severe health issues. This paper presents a case study in Johor Bahru, Malaysia (FOLO Farm), in which a composting prototype is used as the waste management technology to recycle the food and vegetable wastes. The greenhouse gases (GHG) mitigation and economic feasibility of the integrated composting and organic farming in this study are reported. This study showed a reduction of 27% of GHG by diverting the food and vegetable wastes from open dumping to the composting plant. Higher reduction rate (∼44%) can be achieved with better planning of waste collection route and applying the mitigation strategies during the composting process. By adapting the membership concept, this project not only ensures the economic feasibility of running a composting plant but also secures a channel for the growth of vegetable distribution. This study provides an insight into the feasibility and desirability to implement a pilot-scale composting for organic waste management to achieve the low carbon and self-sustain community.
Fast pyrolysis is a potential technology for converting lignocellulosic biomass into bio-oil. Nevertheless, the high amounts of acid, oxygenated compounds, and water content diminish the energy density of the bio-oil and cause it to be unsuitable for direct usage. Catalytic fast pyrolysis (CFP) is able to improve bio-oil properties so that downstream upgrading processes can be economically feasible. Here, calcium oxide (CaO), magnesium oxide (MgO), and zinc oxide (ZnO) were employed due to their potential in enhancing bio-oil properties. The results showed that overall, all three catalysts positively impacted the empty fruit bunch fibre-derived bio-oil properties. Among the catalysts, CaO showed the most favorable effects in terms of reducing the acidity of the bio-oil and anhydrosugar. Thermal stability of bio-oils produced in the presence of CaO was studied as well.