Search

While the potential of biochar (BC) to immobilize potentially toxic elements (PTEs) in contaminated soils has been studied and reviewed, no review has focused on the potential use of BC for enhancing the phytoremediation efficacy of PTE-contaminated soils. Consequently, the overarching purpose in this study is to critically review the effects of BC on the mobilization, phytoextraction, phytostabilization, and bioremediation of PTEs in contaminated soils. Potential mechanisms of the interactions between BC and PTEs in soils are also reviewed in detail. We discuss the promises and challenges of various approaches, including potential environmental implications, of BC application to PTE-contaminated soils. The properties of BC (e.g., surface functional groups, mineral content, ionic content, and π-electrons) govern its impact on the (im)mobilization of PTEs, which is complex and highly element-specific. This review demonstrates the contrary effects of BC on PTE mobilization and highlights possible opportunities for using BC as a mobilizing agent for enhancing phytoremediation of PTEs-contaminated soils.

Empty fruit bunch oil palm (EFBOP) is one of the byproducts after oil palm fruitlet is removed in oil palm processing and is considered as waste. In this study, EFBOP was converted to biochar (BC-EFBOP) at 350-700 °C, with an overarching aim of determining the feasibility of adsorptive removal of manganese (a second dominant element in acid mine draingae) from water. . Results showed that with increasing temperature, the BC-EFBOP yield decreased from 44.34% to 26.74%, along with the H/C (0.89%-0.29%) and O/C ratios (0.38%-0.23%), and the carbon content increased (62.7%-73.93%). As evidenced by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), abundant oxygen-containing surface functional groups such as hydroxyl (-OH), carboxyl (-COOH), and ether (C-O-C) were retained, and aromatic CC groups were largely generated in the biochar. Pyrolysed biochar at 350 °C (BC350), with the least surface area (0.5 m

Over the past few years, persistent organic pollutants (POPs) exhibiting high ecotoxicity have been widely detected in the environment. Persulfate-oxidation hybrid system is one of the most widely used novel advanced oxidation techniques and is based on the persulfate generation of SO

Over the years, the transformation of biomass into a plethora of renewable value-added products has been identified as a promising strategy to fulfil high energy demands, lower greenhouse gas emissions, and exploit under-utilized resources. Techno-economic analysis (TEA) and life-cycle assessment (LCA) are essential to scale up this process while lowering the conversion cost. In this study, trade-offs are made between economic, environmental, and technical indicators produced from these methodologies to better evaluate the commercialization potential of biomass pyrolysis. This research emphasizes the necessity of combining LCA and TEA variables to assess the performance of the early-stage technology and associated constraints. The important findings based on the LCA analysis imply that most of the studies reported in literature focussed on the global warming potentials (GWP) under environmental category by considering greenhouse gases (GHGs) as evaluation parameter, neglecting many other important environmental indices. In addition, the upstream and downstream processes play an important role in understanding the life cycle impacts of a biomass based biorefinery. Under upstream conditions, the use of a specific type of feedstock may influence the LCA conclusions and technical priority. Under downstream conditions, the product utilization as fuels in different energy backgrounds is crucial to the overall impact potentials of the pyrolysis systems. In view of the TEA analysis, investigations towards maximizing the yield of valuable co-products would play an important role in the commercialization of pyrolysis process. However, comprehensive research to compare the conventional, advanced, and emerging approaches of biomass pyrolysis from the economic perspective is currently not available in the literature.

Soil acidification in managed ecosystems such as agricultural lands principally results from the increased releasing of protons (H

Decision Support System (DSS) is a novel approach for smart, sustainable controlling of environmental phenomena and purification processes. Toluene is one of the most widely used petroleum products, which adversely impacts on human health. In this study, Fusarium Solani fungi are utilized as the engine of the toluene bioremediation procedure for the monitoring part of DSS. Experiments are optimized by Central Composite Design (CCD) - Response Surface Methodology (RSM), and the behavior of the mentioned fungi is estimated by M5 Pruned model tree (M5P), Gaussian Processes (GP), and Sequential Minimal Optimization (SMOreg) algorithms as the prediction section of DSS. Finally, the control stage of DSS is provided by integrated Petri Net modeling and Failure Modes and Effects Analysis (FMEA). The findings showed that Aeration Intensity (AI) and Fungi load/Biological Waste (F/BW) are the most influential mechanical and biological factors, with P-value of 0.0001 and 0.0003, respectively. Likewise, the optimal values of main mechanical parameters include AI, and the space between pipes (S) are equal to 13.76 m

The influence of Cl

In order to identify the most environmental-friendly pretreatment for pyrolsis of wood residue to levoglucosan (LG), for the first time a comparative life cycle assessment (LCA) was carried out for hot water treatment (HWT), torrefaction, acid pretreatment (AP) and salt pretreatment (SP) pathways. Since LG production can facilitate both resource recovery (RR) and wood residue handling (WRH), two different functional units (FUs), i.e., 1 kg LG production and 1 kg wood residue handling were considered. AP was found to generate the least global warming potential of 134.60 kg CO

Biochar is produced as a charred material with high surface area and abundant functional groups by pyrolysis, which refers to the process of thermochemical decomposition of organic material at elevated temperatures in the absence of oxygen. The carbon component in biochar is relatively stable, and, hence, biochar was originally proposed as a soil amendment to store carbon in the soil. Biochar has multifunctional values that include the use of it for the following purposes: soil amendment to improve soil health, nutrient and microbial carrier, immobilising agent for remediation of toxic metals and organic contaminants in soil and water, catalyst for industrial applications, porous material for mitigating greenhouse gas emissions and odorous compounds, and feed supplement to improve animal health and nutrient intake efficiency and, thus, productivity. This article provides for the first time an overview of the multifunctional values and unintended consequences of biochar applications. Refereed/Peer-reviewed

Biochar is a solid carbon material produced by heating organic biomass in the absence of oxygen through a process known as pyrolysis. Scientists and policy makers have recognised its potential role in carbon sequestration, reducing greenhouse gas emissions, renewable energy, waste mitigation and as soil amendment. To date, most studies related to biochar application to soil have focused mainly on the agronomic benefits, while little attention is paid on its effects on soil properties from geotechnical point of view. Considering that biochar can be produced from biomass, its use would fit satisfactorily the current trends of recycling wastes for ground improvement and liquefaction mitigation. To address this, the effect of adding various proportions by weight of biochar, derived from poultry litter, on the liquefaction resistance of sand is investigated through undrained cyclic triaxial tests. The findings suggest that, contrary to other earlier published reports using another type of biochar, adding poultry litter biochar to sand decreases its liquefaction resistance in a similar manner as adding non-plastic fines. The results highlight the fact that the type of biochar used as soil amendment is important in determining whether the liquefaction resistance of the host sand will improve or not.

Growing awareness of sustainability in the landfill cover system has increased the use of biochar amendment for degraded landfill surface soils. Hydraulic and vegetative benefits of biochar on cover soil have been studied in the past, while ignoring mechanical characteristics, which is important to understand progressive failure of landfill infrastructure. In this study, the mechanical characteristics of four soil–biochar composites were investigated by conducting 81 unconfined compressive strength test. The results based on four in-house produced biochar were used to study the effect of compaction state (density, moisture content) and biochar percentage (5% and 10%) on unconfined compressive strength of soil–biochar. The ductility of soil–biochar was investigated for all the four biochars. Results from this study indicate a contrasting observation of strength gain depending on the type of biochar. The unconfined compressive strength of soil–biochar is potentially influenced by the different surface functional groups of biochar (hydrophilicity/hydrophobicity) and soil-biochar interlocking. It was noted that the peanut shell biochar gave comparable unconfined compressive strength of soil–biochar with that of bare soil for different compaction state. However, a diminution in the unconfined compressive strength was observed for all the other three soil–biochar sourced from water hyacinth, saw dust, and poultry litter. The study indicates that the use of biochar in soils does not ensure an improvement in the strength of soil–biochar. Enhancement in ductility was found for all the four soil–biochar irrespective of compaction state. Improvement in ductility was maximum when the soil–biochar is compacted at the dry state of optimum. Plant-based biochar has higher potency to increase the ductility of soil as compared to the animal-based biochar. Our study identifies peanut shell biochar ideal for landfill cover amendment material, considering its mechanical characteristics and design criterion. Soil biochar composite from water hyacinth, saw dust, and poultry litter can be used for potential application in green-infrastructure.

Food waste constitutes a remarkable portion of municipal solid waste. About one-third of the global food waste produced is lost with the food supply chain. Food waste in many countries is still dumped of in landfill or incinerated simultaneously with other municipal wastes. Food waste requires proper management and recycling techniques in order to minimise its environmental burden and risk to human life. Despite considerable research on food waste conversion still, there is a shortage of comprehensive reviews of the published literature. In this review, we provide a mini global perspective of food waste with special emphasis on New Zealand and their conversion into the useful material through hydrothermal carbonisation (HTC). Other thermal technologies such as incineration and pyrolysis are also briefly discussed. The review discusses why HTC is more suitable thermal technology than others, which are currently available. Recognising the importance of techno-economic feasibility of HTC, we present a cost analysis on the production of value-added products via HTC with examples taken from the literature to gather information in the feasibility assessment process. Finally, key challenges and future directions for a better productive way of handling food waste are being suggested.

Hazardous wastes disposed of in engineered landfills interact with rainwater, generate harmful leachate and may contaminate groundwater. To minimize this, a suitable multi-layered cover system (MLCS) is constructed over the buried waste. Field assessment of complex moisture dynamics in unsaturated MLCS and its long-term hydraulic efficiency has not been investigated in detail for extremely humid conditions (annual rainfall >1000 mm). Therefore, the overarching purpose of this study was to investigate the long-term hydraulic performance of a three-layered hydraulic barrier cover system under humid Indian conditions. The field cover setup was exposed to natural weather condition in the Northeast Indian state of Assam, for 800 days. The MLCS was instrumented to measure continuous variation of volumetric water content and matric suction as function of time and depth. The field measurements were used to determine the appropriate input hydraulic parameters and evapotranspiration model that can be used for numerical modeling. The results showed that simulation using drying van Genuchten soil-water characteristic curve parameters and Penman-Monteith evapotranspiration model matched the field observations. Events of the highest precipitation and extreme drought (cause for desiccation) did not lead to percolation in the drainage layer (60 cm) and barrier layer (100 cm). Numerical analyses performed for 87 years by considering the climate data of two different humid locations (Eastern and Western part) of India revealed that the progressive saturation of barrier layer occurred within 18 to 20 years. However, when geosynthetic clay liner was incorporated as additional barrier material, the saturation time increased by two-fold (42 to 44 years).

Batch sorption of metformin hydrochloride (MET) onto a specially designed biochar mix consisting of both macro (MAC) and micro (MIC) algae, rice husk and pine sawdust was conducted. Pyrolysis of both MAC and MIC algae mixture was done followed by chemical activation with hydrogen-peroxide. Additionally, sorption of MET under the influence of pH was separately investigated. Batch studies of isotherms were well described by Freundlich model with high non-linearity and Freundlich exponent values ranged anywhere from 0.12 to 1.54. Heterogeneity of MET adsorption to the bonding sites was attributed to the surface functional groups of the modified biochar. Amongst the four biochars, the activated macroalgae biochar (MACAC) and microalgae biochar (MICAC) depicted favourable adsorption of MET with maximum adsorption at pH 7. Up to 76% of MET removal from the environment was obatained using the MACAC biochar. Scanning electron micrographs coupled with energy dispersive X-ray, as well as elemental analyses confirmed formation of oxygen containing surface functional groups due to activation strengthening chemisorption as the main sorption mechanism. Further, Fourier transform infra-red spectroscopy and other surface functional group analyses along with Zeta potential measurements reinforced our proposed sorption mechanism. Lowest zeta potential observed at pH 7 enhanced the electrostatic force of attraction for both the biochars. Negative zeta potential value of the biochars under different pH indicated potential of the biochars to adsorb other positively charged contaminants. From a techno-economic perspective, capital expenditure cost is not readily available, however, it is envisaged that production of pyrolyzed biochar from algal biomass could make the process economically attractive especially when the biochar could be utilised for high-end applications.

The combined action of biochar and C-S-H (calcium-silicate-hydrate) in the cement mortars as adsorbents was explored for treating heavy metals from water. The biochar admixture cement mortars were ground to fines for use as adsorbents with the rationale that combined action of Ca, Si, Al etc. based industrial waste with conventional adsorbent biochar could enhance the removal efficiency of contaminants and therefore the overarching aim was to study the removal capacity for three selected heavy metals (Pb

We investigated the competitive effects of different fractions of wastewater treatment plant effluent organic matter (EfOM) on adsorption of an organic micro pollutant (OMP), propranolol (PRO), in a fixed bed column packed with magnetic tyre char (MTC). The results showed that the presence of EfOM inhibited PRO adsorption in wastewater leading to decreased PRO adsorption capacity from 5.86 to 2.03 mg/g due to competitive effects and pore blockage by smaller EfOM fractions. Characterization of EfOM using size exclusion chromatography (LC-OCD) showed that the principal factor controlling EfOM adsorption was pore size distribution. Low molecular weight neutrals had the highest adsorption onto MTC while humic substances were the least interfering fraction. Effect of important parameters such as contact time, linear velocity and bed height/diameter ratio on MTC performance was studied in large-lab scale columns. Linear velocity and contact time were found to be effective in increasing adsorption capacity of PRO on MTC and delaying breakthrough time. Increase in linear velocity from 0.64 cm/min to 1.29 cm/min increased mass transfer and dispersion, resulting in considerable rise of adsorbed amount (5.86 mg/g to 22.58 mg/g) and increase in breakthrough time (15.8-62.7 h). Efficiency of non-equilibrium Hydrus model considering dispersion and mass transfer mechanism was demonstrated for real wastewater and scale up purposes. Ball milling for degradation of adsorbed PRO and regeneration of MTC resulted in 79% degradation of PRO was achieved after 5 h milling (550 rpm), while the addition of quartz sand increased the efficiency to 92%.

Microplastics (MPs) are ubiquitous in the aquatic environment due to plastic waste proliferation in diverse sectors. The recent years have witnessed exponential growth in the number of studies focusing on their occurrence, distribution and toxicity in several parts of India. The overarching aim of this article is to evaluate the sources, abundance, and characteristics of MPs reported in the sediments, water, and biota of the aquatic ecosystems in India. The review revealed that while the MPs from land-based sources such as littering, domestic sewage, and industrial runoff were carried by rivers and streams, MPs from other sources including marine litter and accidental spillages during shipping directly enter the aquatic environment. The unique hydrodynamic conditions during the southwest and northeast monsoons were found to influence the abundance and distribution of MPs in the Indian aquatic ecosystems. Although the seaward flushing and monsoonal flux were reported to increase the abundance of MPs, the reversal of the winds and currents during the NE monsoon was observed to oppose the drift of MPs towards the Goa coast. The reported higher concentrations of MPs in the beach sediments collected from the high tide line (1323 ​± ​1228 ​mg/m2) as compared to that of low tide line (178 ​± ​261 ​mg/m2) along the southeast coast of India also emphasize the tidal influence. While the shape and type of MPs can help in determining their sources, their size and colour might influence their ingestion in aquatic biota and also indicate the amount of degradation. The variability in the characteristics of MPs observed between different studies could also be a factor of difference in the sampling and analysis techniques adopted. Although the general practice of degutting before consumption could lower the risk of MPs transfer from fish, popular delicacies of dried fish and shrimps could be potential sources of human ingestion. Since the research was mostly confined to the southern coasts of India and some urban recreational beaches, the MP pollution on other coastal regions of India remains largely unexplored. Moreover, with very few studies reporting on the MP pollution in the freshwater ecosystems, the wide network of rivers and enclosed water bodies could also be the major focus of future research.

Microplastics are well known for vector transport of hydrophobic organic contaminants, and there are growing concerns regarding their potential adverse effects on ecosystems and human health. However, recent studies focussing on hydrophilic compounds, such as pharmaceuticals and personal care products (PPCPs), have shown that the compounds ability to be adsorbed onto plastic surfaces. The extensive use of PPCPs has led to their ubiquitous presence in the environment resulting in their cooccurrence with microplastics. The partitioning between plastics and PPCPs and their fate through vector transport are determined by various physicochemical characteristics and environmental conditions of specific matrices. Although the sorption capacities of microplastics for different PPCP compounds have been investigated extensively, these findings have not yet been synthesized and analyzed critically. The specific objectives of this review were to synthesize and critically assess the various factors that affect the adsorption of hydrophilic compounds such as PPCPs on microplastic surfaces and their fate and transport in the environment. The review also focuses on environmental factors such as pH, salinity, and dissolved organics, and properties of polymers and PPCP compounds, and the relationships with sorption dynamics and mechanisms. Furthermore, the ecotoxicological effects of PPCP-sorbed microplastics on biota and human health are also discussed.

An attempt has been made in this review to provide some insights into the possible adsorption mechanisms of hexavalent chromium onto layered double hydroxides-based adsorbents by critically examining the past and present literature. Layered double hydroxides (LDH) nanomaterials are typical dual-electronic adsorbents because they exhibit positively charged external surfaces and abundant interlayer anions. A high positive zeta potential value indicates that LDH has a high affinity to Cr(VI) anions in solution through electrostatic attraction. The host interlayer anions (i.e., Cl−, NO3−, SO42−, and CO32−) provide a high anion exchange capacity (53–520 meq/100 g) which is expected to have an excellent exchangeable capacity to Cr(VI) oxyanions in water. Regarding the adsorption-coupled reduction mechanism, when Cr(VI) anions make contact with the electron-donor groups in the LDH, they are partly reduced to Cr(III) cations. The reduced Cr(III) cations are then adsorbed by LDH via numerous interactions, such as isomorphic substitution and complexation. Nonetheless, the adsorption-coupled reduction mechanism is greatly dependent on: (1) the nature of divalent and trivalent salts utilized in LDH preparation, and the types of interlayer anions (i.e., guest intercalated organic anions), and (3) the adsorption experiment conditions. The low Brunauer–Emmett–Teller specific surface area of LDH (1.80–179 m2/g) suggests that pore filling played an insignificant role in Cr(VI) adsorption. The Langmuir maximum adsorption capacity of LDH (Qomax) toward Cr(VI) was significantly affected by the natures of used inorganic salts and synthetic methods of LDH. The Qomax values range from 16.3 mg/g to 726 mg/g. Almost all adsorption processes of Cr(VI) by LDH-based adsorbent occur spontaneously (ΔG° 0) and increase the randomness (ΔS° >0) in the system. Thus, LDH has much potential as a promising material that can effectively remove anion pollutants, especially Cr(VI) anions in industrial wastewater.

We evaluated wastewater remediation and CO2 utilization potential of Chlorella minutissima from flue gas in a raceway pond, while synthesizing lutein and lipid for potential healthcare and biofuel application. A mix of 20% kitchen waste, 10 g L−1 of poultry litter waste and 5% flue gas was maintained while cultivating the microalga. Complete removal of nitrate, nitrite and ammonium, 85% carbon and 91% phosphorus was observed. An average areal biomass productivity of 4.06 ± 0.12 g m−2 day−1 with a specific growth rate of 0.34 ± 0.03 day−1 was observed within 9 days. Biomass productivity of 6.21 ± 0.16 g m−2 day−1 with a specific growth rate of 0.34 ± 0.03 day−1 was achieved during winter. Furthermore, lipid content with appropriate fatty acid composition 1.04:1 (saturation:unsaturation) increased from 25% to 58%. Additionally, lutein productivity of 1.2 ± 0.08 mgL−1 day−1, while utilizing 80.74 ± 0.07 mg L−1 day−1 of CO2 from 5% flue gas was obtained.

Bisphenols have drawn increasing attention from regulatory agencies and scientific communities due to their widespread occurrences, distribution and endocrine disrupting effects, and severe...

Biochar is a biomass-derived carbonaceous solid product produced by way of pyrolysis, a process whereby thermal degradation of biomass occurs in the absence of or under a limited oxygen environment. To date, little work has been done to assess its effect on soil properties from the geotechnical point of view. A few studies have shown that biochar could increase the shear strength of clays. Results of simple shear tests indicated that although the effect of adding biochar on the drained shear resistance of sand is relatively minor, the liquefaction resistance increased considerably. In this paper, to provide an insight into the mechanism, the interaction between biochar and water was studied in more detail, through an analysis of the biochar chemical active surface, morphological observations of the particles and biochar–water suspension, as well as rheological measurements. It is believed that the mechanism of improvement is related to the active chemicals on the surface and inside the pores of the biochar particles. These volatiles interact with water by repelling it (hydrophobic) and at times by attracting it (hydrophilic), creating a complex network between water and biochar particles that helps to delay the increase in excess pore-water pressure and provides some shear resistance.

Bringing two completely different properties into one nanostructure by using individual metals is a difficult goal to achieve. However, recently core-shell metallic nanostructures have introduced as a novel multifunctional nanomaterial with enhanced properties. Iron and silver based nanoparticles are among the most widely applicable nanomaterials in modern industries. Zero-valent iron nanostructures and silver nanoparticles are well known for their applications as catalyst and antimicrobial agent, respectively. In the present study, for the first time, we are reporting a successful fabrication of zero valent iron coated silver nanoparticles (ZVI@AgNPs) by using a green and one-pot synthesis approach. Aqueous leaf extract of Mediterranean cypress (Cupressus sempervirens) was used as a natural source of reducing and capping agent for reduction of both Ag+ and Fe3+ ions. Prepared nanostructures were characterised by a range of analytical techniques namely UV–vis spectroscopy, Transmission Electron Microscopy, X-Ray Diffraction, and Fourier Transform Infra-Red Spectroscopy. The prepared nanostructures were found to be an effective material for dye removal and were capable to remove 98.5% of the initial dye just after 4 h. Based on the results, zero valent iron coating enhanced the antimicrobial potential of AgNPs against Gram-positive bacteria (S. aureus), while showing no significant enhancement against Gram-negative bacteria (E. coli). ZVI@AgNPs, therefore, can be introduced as a novel nanostructure for application in aquatic filter materials to simultaneously reduce microbial and organic contaminants.

Rapid industrial development and human activities have caused a degradation of soil quality and fertility. There is increasing interest in rehabilitating low fertility soils to improve crop yield and sustainability. Biochar, a carbonaceous material intentionally produced from biomass, is widely used as an amendment to improve soil fertility by retaining nutrients and, potentially, enhancing nutrient bioavailability. But, biochar is not a simple carbon material with uniform properties, so appropriate biochar selection must consider soil type and target crop. In this respect, many recent studies have evaluated several modification methods to maximize the effectiveness of biochar such as optimizing the pyrolysis process, mixing with other soil amendments, composting with other additives, activating by physicochemical processes, and coating with other organic materials. However, the economic feasibility of biochar application cannot be neglected. Strategies for reducing biochar losses and its application costs, and increasing its use efficiency need to be developed. This review synthesized current understanding and introduces holistic and practical approaches for biochar application to low fertility soils, with consideration of economic aspects.

Seasonal variations in the concentrations and fate of 20 selected pharmaceuticals and personal care products (PPCPs) were investigated over one year in a wastewater treatment plant in New Zealand, which relies on a membrane bioreactor (MBR) and Bardenpho as parallel processes for its secondary treatment. Results showed that all of the monitored PPCPs were detected in the wastewater influent. Nonsteroidal anti-inflammatory drugs (NSAIDS) and caffeine were predominant in the influent, whereas in the effluent, β-blockers and benzotriazole were present at significant concentrations. Total PPCPs' concentration in the influent was found to be 130 μg/L. Average removal efficiency was found to be ≥ 99% for acetaminophen, caffeine, TCEP, naproxen, and ibuprofen, whereas

The degradation of metformin (MET) and guanylurea (GUA) fortified separately in freshly collected two top soils (0–10 cm) from New Zealand's pastoral region was studied under controlled laboratory conditions. Incubation studies were carried at 30 °C under aerobic conditions at 60% of maximum water holding capacity and at two (0.5 mg/kg and 5 mg/kg) nominal soil concentrations. Degradation profiles revealed a bi-phasic pattern of both the compounds with an initial rapid degradation followed by slow dissipation rate, resulting in poor fits by simple first order kinetics. However, the use of three non-linear mathematical models sufficiently described the measured data and well supported by an array of statistical indices to judge model's ability to fit the measured datasets. Further evaluation using box-whisker plots showed that double first-order in parallel (DFOP) and first-order two-compartment (FOTC) models best fitted the data points followed by the Bi-exponential (BEXP) model. Mechanistic assumptions from DFOP and FOTC suggest that degradation of MET and GUA proceeds at two different rates, possibly in two compartments. The calculated DT50 using both models were in the range of 2.7–15.5 days and 0.9–4 days, while 90% dissipation time (DT90) varied between 91 and 123 days and 44 and 137 days for MET and GUA, respectively. Degradation of both compounds were dependent on soil types and properties, incubation conditions and initial substrate concentration. Formation of GUA with decrease in MET concentration over time confirmed that GUA is a transformation product concomitantly formed from aerobic degradation of MET in soil.

Elevated levels of potentially toxic elements (PTEs) in aqueous environments have drawn attention recently due to their presence and toxicity to living beings. There have been numerous attempts to remove PTEs from aqueous media. The potential of metal–organic frameworks (MOFs) in removing PTEs from aqueous media has been recognized due to their distinctive advantages (e.g., increased removal capability, large surface area, adjustable porosity, and recyclability). Because of the poor stability of MOFs in water, pre and post synthetic modification and functionalization of MOFs have also been developed for water treatment investigations. This review addresses the performance and mechanisms of PTE removal in various modified MOFs in detail. In order to compare the performance of MOFs, here we used partition coefficient (PC) instead of maximum adsorption capacity, which is sensitively influenced by initial loading concentrations. Therefore, the PC of each material was used to evaluate the adsorption performance of different MOFs and to compare with other sorbents. Furthermore, it discusses the scale-up issues and forthcoming pathway for the research and development needs of MOFs for effective PTE removal. This review further elucidates the main removal mechanisms of PTEs by MOFs. Commercial or domestic water treatment systems or water filters can utilize engineered MOFs to treat water by adsorptive removal. However, marketable products have yet to be investigated thoroughly due to limitations of the large-scale synthesis of MOFs.

The world has entered into the "fourth-generation" of refrigerants, and it is an undeniable fact that we will continue to encounter several issues in identifying a suitable refrigerant that suits the purpose and poses no harm to the environment. The ever-changing regulations on the use of refrigerants have often posed great challenges to the refrigeration industry and there is a pressing need to develop new refrigerants and develop better equipment to use them. Theoretically, an ideal refrigerant should possess characteristics such as low-global warming potential (GWP), non-toxic, non-flammable, and zero-ozone depletion potential (ODP). In addition, the refrigerants are also expected to have excellent thermodynamic and thermophysical properties. Many new synthetic refrigerants have been reported as alternative refrigerants and have very low atmospheric life as well as low GWP and zero-ODP. However, it is irrefutable that most of the studies that reported the so-called new refrigerants are actually not new. From the invention of R-12 (Dichlorodifluoromethane) in 1930s to the invention of R-1234yf in 2000s, these substances are available for decades even before being recognized as refrigerants. This review attempts to provide chronicles on different aspects of refrigerants such as their progress since their invention in the early 1800s, classification and properties. In addition, concepts such as issues associated with the long-term use of refrigerants, barriers for the inclusion of low-GWP refrigerants, various protocols and accords that have occurred since the inception of refrigerants are also critically discussed.

We investigated the potential application of anaerobically digested residues for generating bioenergy in the presence of alkali bifunctional material, sodium zirconate (Na

Conversion of hazardous waste materials to value-added products is of great interest from both agro-environmental and economic points of view. Bone char (BC) has been used for the removal of potentially toxic elements (PTEs) from contaminated water, however, its potential BC for the immobilization of PTEs in contaminated water and soil compared to bone (BBC)- and plant (PBC)-derived biochars has not been reviewed yet. This review presents an elaboration for the potentials of BC for the remediation of PTEs-contaminated water and soil in comparison with PBC and BBC. This work critically reviews the preparation and characterization of BC, BBC, and PBC and their PTEs removal efficiency from water and soils. The mechanisms of PTE removal by BC, BBC, and PBC are also discussed in relation to their physicochemical characteristics. The review demonstrates the key opportunities for using bone waste as feedstock for producing BC and BBC as promising low-cost and effective materials for the remediation of PTEs-contaminated water and soils and also elucidates the possible combinations of BC and BBC aiming to effectively immobilize PTEs in water and soils.

A parametric study employing Taguchi's design of experimental technique was conducted to produce a value added novel biochar mix from three different origin feedstock and evaluate the effect of process parameters on biochar quality. Three feedstocks sourced from different origins (macroalgae: Sargassum sp, agricultural waste: rice husk and lignocellulosic waste: pine wood) were mixed in a definite proportion and pyrolyzed following the L4 experimental layout. Results indicated that temperature and mixing ratio were the most influential contributing factor. A temperature of 500 °C and 70% algae mix was the optimum condition to get an enhanced biochar in terms of thermal stability, aromaticity, pH balance, ash content and yield. Among the 4 Taguchi combination char S3 stands out as the best condition that resulted in high aromaticity, 40% high ash content, highly alkaline pH (10.3), 1–2% higher nitrogen and sulfur content. Potential application of biochar in agronomy as a soil ameliorant and/or in contaminant remediation as an adsorbent is suggested.

Vegetation is known to influence the hydrological state variables, suction $$ \left( \psi \right) $$ and volumetric water content ( $$ \theta_{w} $$ ) of soil. In addition, vegetation induces heterogeneity in the soil porous structure and consequently the relative permeability ( $$ k_{r} $$ ) of water under unsaturated conditions. The indirect method of utilising the soil water characteristic curve (SWCC) is commonly adopted for the determination of $$ k_{r} $$ . In such cases, it is essential to address the stochastic behaviour of SWCC, in order to conduct a robust analysis on the $$ k_{r} $$ of vegetative cover. The main aim of this study is to address the uncertainties associated with $$ k_{r} $$ , using probabilistic analysis, for vegetative covers (i.e., grass and tree species) with bare cover as control treatment. We propose two approaches to accomplish the aforesaid objective. The univariate suction approach predicts the probability distribution functions of $$ {\text{k}}_{\text{r}} $$ , on the basis of identified best probability distribution of suction. The bivariate suction and water content approach deals with the bivariate modelling of the water content and suction (SWCC), in order to capture the randomness in the permeability curves, due to presence of vegetation. For this purpose, the dependence structure of $$ \psi $$ and $$ \theta_{w} $$ is established via copula theory, and the $$ k_{r} $$ curves are predicted with respect to varying levels of $$ \psi - \theta_{w} $$ correlation. The results showed that the $$ k_{r} $$ of vegetative covers is substantially lower than that in bare covers. The reduction in $$ k_{r} $$ with drying is more in tree cover than grassed cover, since tree roots induce higher levels of suction. Moreover, the air entry value of the soil depends on the magnitude of $$ \psi - \theta_{w} $$ correlation, which in turn, is influenced by the type of vegetation in the soil. $$ k_{r} $$ is found to be highly uncertain in the desaturation zone of the relative permeability curve. The stochastic behaviour of $$ k_{r} $$ is found to be most significant in tree covers. Finally, a simplified case study is also presented in order to demonstrate the impact of the uncertainty in $$ k_{r} $$ , on the stability of vegetates slopes. With an increment in the parameter $$ \alpha $$ , factor of safety (FS) is found to decrease. The trend of FS is reverse of this with parameter $$ n $$ . Overall FS is found to vary around 4–5%, for both bare and vegetative slopes.

A solid carbon-rich product hydrochar, was prepared using hydrothermal carbonisation of food waste at temperatures of 200, 250 and 300 °C. To acquire detailed insight into physicochemical and structural properties, hydrochar samples were characterised using a range of techniques. The carbon content and higher heating value of food waste increased considerably from 39 to 73% and 15 to 31 MJ/kg corresponding to the heating temperature. The blends of hydrochar and coal prepared in three different ratios (5%, 10% and 15%) exhibited different thermal behaviour. The overall results of co-combustion study showed that the activation energy of hydrochar samples decreased from 56.78 KJ/mol to 29.80 KJ/mol with increase in temperature. Hydrochar prepared at 300 °C with coal blending ratio of 10% exhibited the lowest activation energy of 19.45 KJ/mol. Additionally thermal gravimetric analysis of the samples showed that high temperature carbonization can increase the combustion properties of hydrochar.