A low-cost fruit waste namely watermelon peel (WMP) was utilized as a promising precursor for the preparation of mesoporous activated carbon (WMP-AC) via microwave assisted-K2CO3 activation. The WMP-AC was applied as an adsorbent for methylene blue dye (MB) removal. Several types of characterizations, such as specific surface area (BET), Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy (SEM-EDX), Elemental Analysis (CHNS/O), and Fourier Transform Infrared Spectroscopy (FTIR) were used to identify the physicochemical properties of WMP-AC. Furthermore, Box-Behnken design (BBD) was applied to optimize the influence of the adsorption operational variables (contact time, adsorbent dose, working temperature, and solution pH) on MB dye adsorption. Thus, based on significant interactions, the optimum BBD output shows the best removal of 50 mg·L-1 MB (92%) was recorded at an adsorbent dose of 0.056 g, contact time of 4.4 min, working temperature of 39 °C, and solution pH 8.4. The Langmuir uptake capacity of WMP-AC was found to be 312.8 mg·g-1, with the best fitness to the pseudo-second-order kinetics model and an endothermic adsorption process. The adsorption mechanisms of MB by WMP-AC can be assigned to the hydrogen bonding, electrostatic attraction, and π-π stacking. The findings of this study indicate that WMP is a promising precursor for producing porous activated carbon for MB dye removal.
This research aims to convert pomegranate peel (PP) into microporous activated carbon (PPAC) using a microwave assisted K2CO3 activation method. The optimum activation conditions were carried out with a 1:2 PP/K2CO3 impregnation ratio, radiation power 800 W, and 15 min irradiation time. The statistical Box-Behnken design (BBD) was employed as an effective tool for optimizing the factors that influence the adsorption performance and removal of methylene blue (MB) dye. The output data of BBD with a desirability function indicate a 94.8% removal of 100 mg/L MB at the following experimental conditions: PPAC dose of 0.08 g, solution pH of 7.45, process temperature of 32.1 °C, and a time of 30 min. The pseudo-second order (PSO) kinetic model accounted for the contact time for the adsorption of MB. At equilibrium conditions, the Freundlich adsorption isotherm describes the adsorption results, where the maximum adsorption capacity of PPAC for MB dye was 291.5 mg g-1. This study supports the utilization of biomass waste from pomegranate peels and conversion into renewable and sustainable adsorbent materials. As well, this work contributes to the management of waste biomass and water pollutant sequestration.
As chromium (Cr) in ecosystems affects human health through food chain exposure, phytoremediation is an environmentally friendly and efficient way to reduce chromium pollution in the environment. Here, we review the mechanism of absorption, translocation, storage, detoxification, and regulation of Cr in plants. The Cr(VI) form is more soluble, mobile, and toxic than Cr(III), reflecting how various valence states of Cr affect environmental risk characteristics, physicochemical properties, toxicity, and plant uptake. Plant root's response to Cr exposure leads to reactive oxygen species (ROS) generation and apoptosis. Cell wall immobilization, vacuole compartmentation, interaction of defense proteins and organic ligand with Cr, and removal of reactive oxygen species by antioxidants continue plant life. In addition, the combined application of microorganisms, genetic engineering, and the addition of organic acids, nanoparticles, fertilization, soil amendments, and other metals could accelerate the phytoremediation process. This review provides efficient methods to investigate and understand the complex changes of Cr metabolism in plants. Preferably, fast-growing, abundantly available biomass species should be modified to mitigate Cr pollution in the environment as these green and efficient remediation technologies are necessary for the protection of soil and water ecology.
Due to their widespread occurrence and detrimental effects on human health and the environment, endocrine-disrupting hazardous chemicals (EDHCs) have become a significant concern. Therefore, numerous physicochemical and biological remediation techniques have been developed to eliminate EDHCs from various environmental matrices. This review paper aims to provide a comprehensive overview of the state-of-the-art remediation techniques for eliminating EDHCs. The physicochemical methods include adsorption, membrane filtration, photocatalysis, and advanced oxidation processes. The biological methods include biodegradation, phytoremediation, and microbial fuel cells. Each technique's effectiveness, advantages, limitations, and factors affecting their performance are discussed. The review also highlights recent developments and future perspectives in EDHCs remediation. This review provides valuable insights into selecting and optimizing remediation techniques for EDHCs in different environmental matrices.
The rapid growth of population and economy has led to an increase in urban air pollutants, greenhouse gases, energy shortages, environmental degradation, and species extinction, all of which affect ecosystems, biodiversity, and human health. Atmospheric pollution sources are divided into direct and indirect pollutants. Through analysis of the sources of pollutants, the self-functioning of different plants can be utilized to purify the air quality more effectively. Here, we explore the absorption of greenhouse gases and particulate matter in cities as well as the reduction of urban temperatures by plants based on international scientific literature on plant air pollution mitigation, according to the adsorption, dust retention, and transpiration functions of plants. At the same time, it can also reduce the occurrence of extreme weather. It is necessary to select suitable tree species for planting according to different plant functions and environmental needs. In the context of tight urban land use, the combination of vertical greening and urban architecture, through the rational use of plants, has comprehensively addressed urban air pollution. In the future, in urban construction, attention should be paid to the use of heavy plants and the protection and development of green spaces. Our review provides necessary references for future urban planning and research.
Treatment of petroleum-contaminated soil to a less toxic medium via physical and chemical treatment is too costly and requires posttreatment. This review focuses on the employment of phytoremediation and mycoremediation technologies in cleaning hydrocarbon-contaminated soil which is currently rare. It is considered environmentally beneficial and possibly cost-effective as it implements the synergistic interaction between plants and biosurfactant producing mycorrhiza to degrade hydrocarbon contaminants. This review also covers possible sources of hydrocarbon pollution in water and soil, toxicity effects, and current technologies for hydrocarbon removal and degradation. In addition to these problems, this review also discusses the challenges and opportunities of transforming the resultant treated sludge and treating plants into potential by-products for a higher quality of life for future generations.
Biochar produced from lignocellulosic biomass offers an opportunity to recycle waste into a valuable soil amendment. The application of biochar has been proposed to mitigate climate change by sequestering carbon in the soil. However, the field impact of biochar treatment on the cellulolytic microbial populations involved in the earlier steps of cellulose degradation is poorly understood. A field trial spanning three consecutive crop cycles of Zea mays was conducted in a degraded tropical Ultisol of Peninsular Malaysia. The soil was amended with two contrasting biochar made from oil palm kernel shells (pyrolyzed at 400°C) and rice husks (gasified at 800°C) with or without fertilizer supplementation. Soil samples were taken at each harvesting stage and analyzed for total organic carbon, labile active organic carbon, total cellulase, and β-glucosidase. Microbial glycoside hydrolase family 6 (GH6) cellulase genes and transcripts, involved in the early steps of cellulose degradation, were quantified from the extracted soil deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), respectively. Total organic carbon, labile active organic carbon, and β-glucosidase activity were significantly increased, while no effect on total cellulase activity was found. Both biochars stimulated the total population (DNA-derived) abundance of soil microorganisms harboring the GH6 cellulase genes. The biochar amendment did not affect the active population (RNA-derived) of the GH6 cellulolytic community, showing no significant changes in transcript expression. This indirectly corroborates the role of biochar as a potential carbon sequester in the soil.
Industrial and urban modernization processes generate significant amounts of heavy metal wastewater, which brings great harm to human production and health. The biotechnology developed in recent years has gained increasing attention in the field of wastewater treatment due to its repeatable regeneration and lack of secondary pollutants. Pseudomonas, being among the several bacterial biosorbents, possesses notable benefits in the removal of heavy metals. These advantages encompass its extensive adsorption capacity, broad adaptability, capacity for biotransformation, potential for genetic engineering transformation, cost-effectiveness, and environmentally sustainable nature. The process of bacterial adsorption is a complex phenomenon involving several physical and chemical processes, including adsorption, ion exchange, and surface and contact phenomena. A comprehensive investigation of parameters is necessary in order to develop a mathematical model that effectively measures metal ion recovery and process performance. The aim of this study was to explore the latest advancements in high-tolerance Pseudomonas isolated from natural environments and evaluate its potential as a biological adsorbent. The study investigated the adsorption process of this bacterium, examining key factors such as strain type, contact time, initial metal concentration, and pH that influenced its effectiveness. By utilizing dynamic mathematical models, the research summarized the biosorption process, including adsorption kinetics, equilibrium, and thermodynamics. The findings indicated that Pseudomonas can effectively purify water contaminated with heavy metals and future research will aim to enhance its adsorption performance and expand its application scope for broader environmental purification purposes.
Dye decolorization through biological treatment techniques has been gaining momentum as it is based on suspended and attached growth biomass in both batch and continuous modes. Hence, this review focused on the contribution of moving bed biofilm reactors (MBBR) in dye removal. MBBR have been demonstrated to be an excellent technology for pollution extraction, load shock resistance, and equipment size and energy consumption reduction. The review went further to highlight different biocarrier materials for biofilm development this review identified biochar as an innovative and environmentally friendly material produced through the application of different kinds of reusable or recyclable wastes and biowastes. Biochar as a carbonized waste biomass could be a better competitor and environmentally friendly substitute to activated carbon given its lower mass costs. Biochar can be easily produced particularly in rural locations where there is an abundance of biomass-based trash. Given that circular bioeconomy lowers dependency on natural resources by turning organic wastes into an array of useful products, biochar empowers the creation of competitive goods. Thus, biochar was identified as a novel, cost-effective, and long-term management strategy since it brings about several essential benefits, including food security, climate change mitigation, biodiversity preservation, and sustainability improvement. This review concludes that integrating two treatment methods could greatly lead to better color, organic matter, and nutrients removal than a single biological MBBR treatment process.
Contamination of rice by arsenic represents a significant human health risk. Roxarsone -bearing poultry manure is a major pollution source of arsenic to paddy soils. A mesocosm experiment plus a laboratory experiment was conducted to reveal the role of rainwater-borne H2O2 in the degradation of roxarsone in paddy rice soils. While roxarsone could be degraded via chemical oxidation by Fenton reaction-derived hydroxyl radical, microbially mediated decomposition was the major mechanism. The input of H2O2 into the paddy soils created a higher redox potential, which favored certain roxarsone-degrading and As(III)-oxidizing bacterial strains and disfavored certain As(V)-reducing bacterial strains. This was likely to be responsible for the enhanced roxarsone degradation and transformation of As(III) to As(V). Fenton-like reaction also tended to enhance the formation of Fe plaque on the root surface, which acted as a filter to retain As. The dominance of As(V) in porewater, combined with the filtering effect of Fe plaque significantly reduced the uptake of inorganic As by the rice plants and consequently its accumulation in the rice grains. The findings have implications for developing management strategies to minimize the negative impacts from the application of roxarsone-containing manure for fertilization of paddy rice soils.
The impact of biological activated carbon (BAC), sand filtration (SF) and biological aerated filter (BAF) for removal of the selected organic micropollutants and polyfluoroalkyl substances (PFASs) from secondary effluent was studied. BAC led to greater removal of dissolved organic carbon (43%) than BAF (30%) which in turn was greater than SF (24%). All biological filtration systems could effectively remove most of the selected organic micropollutants, and there was a greater removal of these micropollutants by BAC (76-98%) than BAF (70-92%) or SF (68-90%). It was found that all treatment was effective for removal of the hydrophobic (log D > 3.2) and readily biodegradable organic micropollutants. The major mechanism for the removal of these molecules was biodegradation by the micro-organism and sorption by the biofilm. Compared to organic micropollutants removal, there was a lower removal of PFASs by all treatments, and BAF and SF had a considerably lower removal than BAC treatment. The better removal for all molecule types by BAC was due to additional adsorption capacity by the activated carbon. This study demonstrated that the BAC process was most effective in removing organic micropollutants present in the secondary effluent.
The unceasing rise of greenhouse gas emission has led to global warming and climate change. Global concern on this phenomenon has put forward the microalgal-based CO2 sequestration aiming to sequester carbon back to the biosphere, ultimately reducing greenhouse effects. Microalgae have recently gained enormous attention worldwide, to be the valuable feedstock for renewable energy production, due to their high growth rates, high lipid productivities and the ability to sequester carbon. The photosynthetic process of microalgae uses atmospheric CO2 and CO2 from flue gases, to synthesize nutrients for their growth. In this review article, we will primarily discuss the efficiency of CO2 biosequestration by microalgae species, factors influencing microalgal biomass productions, microalgal cultivation systems, the potential and limitations of using flue gas for microalgal cultivation as well as the bio-refinery approach of microalgal biomass.
Major concern about the presence of fluoranthene, which consists of four fused benzene rings, in the environment has been raised in the past few years due to its toxic, mutagenic, and persistent organic pollutant properties. In this study, we investigated the removal of fluoranthene under static and agitated conditions. About 89% fluoranthene was removed within 30 days under the agitated condition, whereas under the static condition, only 54% fluoranthene was removed. We further investigated the behavior and mechanism of fluoranthene biosorption and biotransformation by Pleurotus eryngii F032 to accelerate the elimination of fluoranthene. The optimum conditions for the elimination of fluoranthene by P. eryngii F032 included a temperature of 35 °C, pH 3, 0.2% inoculum concentration, and a C/N ratio of 16. Under these conditions at the initial fluoranthene concentration of 10 mg/L, more than 95% of fluoranthene was successfully removed within 30 days. Of those factors influencing the biodegradation of fluoranthene, salinity, glucose, and rhamnolipid content were of the greatest importance. Degradation metabolites identified using gas chromatography-mass spectrometry were 1-naphthalenecarboxylic acid and salicylic acid, suggesting possible metabolic pathways. Finally, it can be presumed that the major mechanism of fluoranthene elimination by white-rot fungi is to mineralize polycyclic aromatic hydrocarbons via biotransformation enzymes like laccase.
The ability of non-living biomass of an arsenic-hypertolerant Bacillus cereus strain SZ2 isolated from a gold mining environment to adsorb As (III) from aqueous solution in batch experiments was investigated as a function of contact time, initial As (III) concentration, pH, temperature and biomass dosage. Langmuir model fitted the equilibrium data better in comparison to Freundlich isotherm. The maximum biosorption capacity of the sorbent, as obtained from the Langmuir isotherm, was 153.41 mg/g. The sorption kinetic of As (III) biosorption followed well the pseudo-second-order rate equation. The Fourier transform infrared spectroscopy analysis indicated the involvement of hydroxyl, amide and amine groups in As (III) biosorption process. Field emission scanning electron microscopy-energy dispersive X-ray analysis of the non-living B. cereus SZ2 biomass demonstrated distinct cell morphological changes with significant amounts of As adsorbed onto the cells compared to non-treated cells. Desorption of 94 % As (III) was achieved at acidic pH 1 showing the capability of non-living biomass B. cereus SZ2 as potential biosorbent in removal of As (III) from arsenic-contaminated mining effluent.
The potential of three submerged aquatic plant species (Cabomba piauhyensis, Egeria densa, and Hydrilla verticillata) to be used for As, Al, and Zn phytoremediation was tested. The plants were exposed for 14 days under hydroponic conditions to mine waste water effluents in order to assess the suitability of the aquatic plants to remediate elevated multi-metals concentrations in mine waste water. The results show that the E. densa and H. verticillata are able to accumulate high amount of arsenic (95.2%) and zinc (93.7%) and resulted in a decrease of arsenic and zinc in the ambient water. On the other hand, C. piauhyensis shows remarkable aluminium accumulation in plant biomass (83.8%) compared to the other tested plants. The ability of these plants to accumulate the studied metals and survive throughout the experiment demonstrates the potential of these plants to remediate metal enriched water especially for mine drainage effluent. Among the three tested aquatic plants, H. verticillata was found to be the most applicable (84.5%) and suitable plant species to phytoremediate elevated metals and metalloid in mine related waste water.
The research conducted a study on decomposition and biodegradability enhancement of textile wastewater using a combination of electron beam irradiation and activated sludge process. The purposes of this research are to remove pollutant through decomposition and to enhance the biodegradability of textile wastewater. The wastewater is treated using electron beam irradiation as a pre-treatment before undergo an activated sludge process. As a result, for non-irradiated wastewater, the COD removal was achieved to be between 70% and 79% after activated sludge process. The improvement of COD removal efficiency increased to 94% after irradiation of treated effluent at the dose of 50 kGy. Meanwhile, the BOD(5) removal efficiencies of non-irradiated and irradiated textile wastewater were reported to be between 80 and 87%, and 82 and 99.2%, respectively. The maximum BOD(5) removal efficiency was achieved at day 1 (HRT 5 days) of the process of an irradiated textile wastewater which is 99.2%. The biodegradability ratio of non-irradiated wastewater was reported to be between 0.34 and 0.61, while the value of biodegradability ratio of an irradiated wastewater increased to be between 0.87 and 0.96. The biodegradability enhancement of textile wastewater is increased with increasing the doses. Therefore, an electron beam radiation holds a greatest application of removing pollutants and also on enhancing the biodegradability of textile wastewater.
The effect of initial dissolved oxygen concentration (IDOC) on Fenton's reagent degradation of a dyestuff, Reactive Black 5 was explored in this study. The study was designed, conducted and analysed based on Central Composite Rotatable Design using a 3-1 lab-scale reactor. The participation of O2 in the process was experimentally observed and appears to be affected by the dosage of the reagents used in the study. The IDOC was found to have a significant influence on the process. Reducing the IDOC from 7.5 mg l(-1) to 2.5 mg l(-1) increased the removal of TOC by an average of about 10%. Reduction of IDOC from 10 mg l(-1) to 0 mg l(-1) enhanced the TOC removal by about 30%. The negative influence of IDOC is likely to be caused by the competition between the O2 and the reagents for the organoradicals. A model describing the relationship between initial TOC removal, reagent dosage and IDOC has also been developed.
Acinetobacter haemolyticus, a Gram-negative aerobic locally isolated bacterium, immobilized on wood-husk showed the ability to detoxify Cr(VI) to Cr(III). Wood-husk, a natural cellulose-based support material, packed in an upward-flow column was used as support material for bacterial attachment. Around 97% of the Cr(VI) in wastewater containing 15 mg L(-1) of Cr(VI) was reduced at a flow rate of 8.0 mL min(-1). The wastewater containing Cr(VI) was added with liquid pineapple wastewater as nutrient source for the bacteria. Electron microscopic examinations of the wood-husk after 42 days of column operation showed gradual colonization of the wood-husk by bacterial biofilm. The use of 0.1% (v/v) formaldehyde as a disinfecting agent inhibited growth of bacteria present in the final wastewater discharge. This finding is important in view of the ethical code regarding possible introduction of exogenous bacterial species into the environment.
Cellulase production was carried out by solid state bioconversion (SSB) method using rice straw, a lignocellulosic material and agricultural waste, as the substrate of three Trichoderma spp. and Phanerochaete chrysosporium in lab-scale experiments. The results were compared to select the best fungi among them for the production of cellulase. Phanerochaete chrysosporium was found to be the best among these species of fungi, which produced the highest cellulase enzyme of 1.43 IU/mL of filter paper activity (FPase) and 2.40 IU/mL of carboxymethylcellulose activity (CMCase). The "glucosamine" and "reducing sugar" parameters were observed to evaluate the growth and substrate utilization in the experiments. In the case of Phanerochaete Chrysosporium, the highest glucosamine concentration was 1.60 g/L and a high concentration of the release of reducing sugar was measured as 2.58 g/L obtained on the 4th day of fermentation. The pH values were also recorded. The range of the pH was about 5.15 to 5.56 in the case of Phanerochaete Chrysosporium.
The process for the production of biodegradable plastic material (polyhydroxyalkanoates, PHAs) from microbial cells by mixed-bacterial cultivation using readily available waste (renewable resources) is the main consideration nowadays. These observations have shown impressive results typically under high carbon fraction, COD/N and COD/P (usually described as nutrient-limiting conditions) and warmest temperature (moderate condition). Therefore, the aim of this work is predominantly to select mixed cultures under high storage responded by cultivation on a substrate - non limited in a single batch reactor with shortest period for feeding and to characterize their storage response by using specific and kinetics determination. In that case, the selected-fixed temperature is 30 degrees C to establish tropical conditions. During the accumulated steady-state period, the cell growth was inhibited by high PHA content within the cells because of the carbon reserve consumption. From the experiments, there is no doubt about the PHA accumulation even at high carbon fraction ratio. Apparently, the best accumulation occurred at carbon fraction, 160 +/- 7.97 g COD/g N (PHAmean, = 44.54% of dried cells). Unfortunately, the highest PHA productivity was achieved at the high carbon fraction, 560 +/- 1.62 g COD/g N (0.152 +/- 0.17 g/l. min). Overall results showed that with high carbon fraction induced to the cultivation, the PO4 and NO3 can remove up to 20% in single cultivation.