Enhanced adsorption of Cu(II) and Zn(II) from aqueous solution by polyethyleneimine modified straw hydrochar

Comparative Study for Propranolol Adsorption on the Biochars from Different Agricultural Solid Wastes

Currently, large amounts of agricultural solid wastes have caused serious environmental problems. Agricultural solid waste is made into biochar by pyrolysis, which is an effective means of its disposal. As the prepared biochar has a good adsorption capacity, it is often used to treat pollutants in water, such as heavy metals and pharmaceuticals. PRO is an emerging contaminant in the environment today. However, there are limited studies on the interaction between biochars with PRO. Thus, in this study, we investigate the adsorption of PRO onto the biochars derived from three different feedstocks. The order of adsorption capacity was corn stalk biochar (CS, 10.97 mg/g) > apple wood biochar (AW, 10.09 mg/g) > rice husk biochar (RH, 8.78 mg/g). When 2 < pH < 9, the adsorption capacity of all the biochars increased as the pH increased, while the adsorption decreased when pH > 9, 10 and 10.33 for AW, CS and RH, respectively. The adsorption of PRO on biochars was reduced with increasing Na+ and Ca2+ concentrations from 0 to 200 mg·L-1. The effects of pH and coexisting ions illustrated that there exist electrostatic interaction and cation exchange in the process. In addition, when HA concentration was less than 20 mg/L, it promoted the adsorption of PRO on the biochars; however, when the concentration was more than 20 mg/L, its promoting effect was weakened and gradually changed into an inhibitory effect. The adsorption isotherm data of PRO by biochars were best fitted with the Freundlich model, indicating that the adsorption process is heterogeneous adsorption. The adsorption kinetics were fitted well with the pseudo-second-order model. All the results can provide new information into the adsorption behavior of PRO and the biochars in the aquatic environment and a theoretical basis for the large-scale application of biochar from agricultural solid wastes.

Competitive adsorption of heavy metals onto xanthate-modified sludge hydrochar and its solidification as secondary minerals

In this study, a sulfur-modified magnetic hydrochar was synthesized by grafting thiol-containing groups onto the sludge-derived hydrochar. The modified hydrochar exhibited effective adsorption of Cu2+, Pb2+, Zn2+, and Cd2+ over a wide pH range and in the presence of coexisting ions, and showed almost no secondary leaching in three acidic solutions. In the mult-metal ion system, the modified hydrochar exhibited maximum adsorption capacities were 39.38, 105.74, 26.53, and 38.11 mg g-1 for Cu2+, Pb2+, Zn2+, and Cd2+, respectively. However, the binding capacity and adsorption amount of modified hydrochar for metal ions were lower in the mult-metal ion system compared to the unit-metal ion system. Notably, Pb2+ showed a strong inhibitory effect on the adsorption of other heavy metal ions by modified hydrochar due to strong competition for xanthate functional groups. The Pb2+ occupied the xanthate and native functional groups (-OH, -NH2, and Fe-O etc.), leaving only a small amount of adsorption sites for Cu2+, Zn2+ and Cd2+. Simulation results further supported these findings, indicating that Pb2+ had the highest density profiles near the four functional groups, and the density profiles of the four heavy metals near the xanthate functional groups were greater compared to the other three functional groups. Furthermore, the SEM-EDS, TOF-SIMI, and XPS results indicated that modified hydrochar achieved excellent mineral binding mainly through electrostatic interaction, ion exchange, and chelation. Overall, these results highlight the sulfur-modified magnetic hydrochar as a highly efficient adsorbent for heavy metals in environmental applications.

Towards Negative Emissions: Hydrothermal Carbonization of Biomass for Sustainable Carbon Materials

The contemporary production of carbon materials heavily relies on fossil fuels, contributing significantly to the greenhouse effect. Biomass is a carbon-neutral resource whose organic carbon is formed from atmospheric CO2. Employing biomass as a precursor for synthetic carbon materials can fix atmospheric CO2 into solid materials, achieving negative carbon emissions. Hydrothermal carbonization (HTC) presents an attractive method for converting biomass into carbon materials, by which biomass can be transformed into materials with favorable properties in a distinct hydrothermal environment, and these carbon materials have made extensive progress in many fields. However, the HTC of biomass is a complex and interdisciplinary problem, involving simultaneously the physical properties of the underlying biomass and sub/supercritical water, the chemical mechanisms of hydrothermal synthesis, diverse applications of resulting carbon materials, and the sustainability of the entire technological routes. This review starts with the analysis of biomass composition and distinctive characteristics of the hydrothermal environment. Then, the factors influencing the HTC of biomass, the reaction mechanism, and the properties of resulting carbon materials are discussed in depth, especially the different formation mechanisms of primary and secondary hydrochars. Furthermore, the application and sustainability of biomass-derived carbon materials are summarized, and some insights into future directions are provided.

A New Approach of Complexing Polymers Used for the Removal of Cu2+ Ions

This study presents two modified polymers for Cu2+ ion removal from aqueous media. Shredded maize stalk (MC) and a strong-base anionic resin (SAX) were modified with indigo carmine (IC) in order to obtain two different complexing polymers, i.e., IC-MC and SAX-IC. Initially, the complex reaction between IC and Cu2+ in the solution was studied. Additionally, the complex formation Cu2+-IC in liquid solutions was evaluated at different pH ranges of 1.5, 4.0, 6.0, 8.0, and 10.0, respectively. For Cu2+ ions, adsorption onto the IC-MC and IC-SAX batch experiments were conducted. The contact time for evaluating the optimum adsorption for Cu2+ ions on the complexing materials was established at 1 h. Efficient Cu2+ ion adsorption on the IC-MC and SAX-IC at pH = 10 was achieved. The adsorption of Cu2+ ions depends on the quantity of IC retained on MC and SAX. At 2.63 mg IC/g MC(S4) and 22 mg IC/g SAX(SR2), a high amount of Cu2+ ion adsorption was reported. The highest adsorption capacity (Qe) of IC-MC was obtained at 0.73 mg/g, and for IC-SAX, it was attained at 10.8 mg/g. Reusability experiments were performed using the HCl (0.5 M) solution. High regeneration and reusability studies of IC-MC and IC-SAX were confirmed, suggesting that they can be used many times to remove Cu2+ ions from aqueous matrices. Therefore, the development of complexing materials could be suitable for Cu2+ ion removal from wastewater.

A review: Hydrochar as potential adsorbents for wastewater treatment and CO2 adsorption

To valorize the biomass and organic waste, hydrothermal carbonization (HTC) stands out as a highly efficient and promising pathway given its intrinsic advantages over other thermochemical processes. Hydrochar, as the main product obtained from HTC, is widely applied as a fuel source and soil conditioner. Aside from these applications, hydrochar can be either directly used or modified as bio-adsorbents for environmental remediation. This potential arises from its tunable surface chemistry and its suitability to act as a precursor for activated or engineered carbon. In view of the importance of this topic, this review offers a thorough examination of the research progress for using hydrochar and its modified forms to remove organic dyes (cationic and anionic dyes), heavy metals, herbicides/pesticides, pharmaceuticals, and CO2. The review also sheds light on the fundamental chemistry involved in HTC of biomass and the major analytical techniques applied for understanding surface chemistry of hydrochar and modified hydrochar. The knowledge gaps and potential hurdles are identified to highlight the challenges and prospects of this research field with a summary of the key findings from this review. Overall, this article provides valuable insights and directives and pinpoints the areas meriting further investigation in the application potential of hydrochar in wastewater management and CO2 capture.

Robust functionalized cellulose-based porous composite for efficient capture and ultra-fast desorption of aqueous heavy metal pollution

The heavy metal pollution control industry requires convenient and cost-effective solutions to address complex aqueous environment. Adsorption method can be an effective strategy to realize these goals. Considering the importance of environmental and sustainable development strategies, there is an urgent need to develop efficient, green and non-toxic heavy metal adsorbents. In this work, a robust aminated cellulose-based porous adsorbent (PGPW) was developed from delignified wood and amino-rich polymer using a solvent-free, mild, simple and efficient preparation method. Such adsorbent exhibited excellent adsorption capacity (188.68 mg g-1) for Cu(II), and its adsorption behavior was consistent with pseudo-second order kinetic and Langmuir isotherm models. Notably, PGPW with superior compressibility could be squeezed to achieve rapid desorption and reach equilibrium within 5 min, while still retaining 87 % adsorption efficiency after 50 cycles. In addition, PGPW showed remarkable selectivity towards various coexisting ionic systems and demonstrated a considerable adsorption capacity in natural water applications. The adsorption mechanism of heavy metal ions on porous adsorption material was elucidated. This approach provides a simple, gentle and sustainable strategy for preparing functionalized wood-based composites with efficient adsorption and ultra-fast desorption of heavy metal ions.

Adsorption of tetracycline by polycationic straw: Density functional theory calculation for mechanism and machine learning prediction for tetracyclines' remediation

The abuse of antibiotics causes serious environmental pollution, whose removal has become a hot topic. The adsorption of tetracycline (TC) on a prepared polycationic straw (MMS) was investigated. The kinetic, thermodynamic and adsorption isotherm models showed that adsorption of TC by MMS was a spontaneous, monolayer reaction with coexistence of physical and chemical process. Density functional theory indicated that the adsorption of TC resulted from electrostatic interaction and hydrogen bonds, which proved the mechanism of TC by macromolecular biomass for the first time. The expected and empirical values of TC adsorption showed a high fit degree, through predication of machine learning, indicating the feasibility and avoiding lots of experiments. Further, the adsorption ability of MMS to other TCs was predicted, founding that the highest removal efficiency was doxycycline, which provides a novel strategy for removal of other pollution and reduce of economic and time cost in practical application.

Hydrochar-nanoparticle integration for arsenic removal from wastewater: Challenges, possible solutions, and future horizon

Arsenic (As) contamination poses a significant threat to human health, ecosystems, and agriculture, with levels ranging from 12 to 75% attributed to mine waste and stream sediments. This naturally element is abundant in Earth's crust and gets released into the environment through mining and rock processing, causing ≈363 million people to depend on As-contaminated groundwater. To combat this issue, introducing a sustainable hydrochar system has achieved a remarkable removal efficiency of over 92% for arsenic through adsorption. This comprehensive review presents an overview of As contamination in the environment, with a specific focus on its impact on drinking water and wastewater. It delves into the far-reaching effects of As on human health, ecosystems, aquatic systems, and agriculture, while also exploring the effectiveness of existing As treatment systems. Additionally, the study examines the potential of hydrochar as an efficient adsorbent for As removal from water/wastewater, along with other relevant adsorbents and biomass-based preparations of hydrochar. Notably, the fusion of hydrochar with nanoparticle-centric approaches presents a highly promising and environmentally friendly solution for achieving the removal of As from wastewater, exceeding >99% efficiency. This innovative approach holds immense potential for advancing the realms of green chemistry and environmental restoration. Various challenges associated with As contamination and treatment are highlighted, and proposed solutions are discussed. The review emphasizes the urgent need to advance treatment technologies, improve monitoring methods, and enhance regulatory frameworks. Looking outlook, the article underscores the importance of fostering research efforts, raising public awareness, and fostering interdisciplinary collaboration to address this critical environmental issue. Such efforts are vital for UN Sustainable Development Goals, especially clean water and sanitation (Goal 6) and climate action (Goal 13), crucial for global sustainability.

Removing DOM from chloride modified hydrochar could improve Cu2+ adsorption capacity from aqueous solution

The behavior and composition of hydrochar-based dissolved organic matter (DOM) would affect the efficiency of copper (Cu) removal from wastewater through adsorption. In this study, the reed was hydrolyzed in the presence of feedwater with and without ZnCl2, FeCl3, and SnCl4 to produce pristine hydrochars (PHCs), which were named H2O-HC, ZnCl2-HC, FeCl3-HC, and SnCl4-HC. After removal of DOM, washed hydrochars (WHCs) were obtained, labelled as W-H2O-HC, W-ZnCl2-HC, W-FeCl3-HC, and W-SnCl4-HC. The release dynamics of DOM from PHCs were analyzed, and the adsorption behaviors of Cu2+ on both PHCs and WHCs were investigated. The results showed that chloride-modifications were beneficial for the porosity, specific surface area (SSA), and functional groups of WHCs. Meanwhile, the quantity of hydrochar-based DOM was significantly affected by chloride-modifications. In particular, the relative contents of Ar-P and Fa-L in the DOM released from hydrochars varied with time and modification. Furthermore, the Qe of Cu2+ adsorption on WHCs followed the order of W-SnCl4-HC > W-FeCl3-HC > W-ZnCl2-HC > W-H2O-HC at 15 °C. Compared to PHCs, the adsorption capacity of Cu2+ on WHCs was improved by 7.15-119.77% at the temperature of 35 °C. Simultaneously, the adsorption capacity of Cu2+ in WHCs showed a significant correlation with the SSA via physical adsorption (P < 0.05). Moreover, XPS analysis revealed that Cu2+ adsorption also occurred via complexation and chelation through newly formed Cu-O group between W-SnCl4-HC and Cu2+. Notably, the increase of Cu2+ adsorption in WHCs was significantly correlated with the release of Fa-L and Ar-P from PHCs (P < 0.05). This study found that the content and composition of hydrochar-based DOM could be a major driving factor for Cu2+ adsorption.

A review on adsorption of heavy metals from wastewater using carbon nanotube and graphene-based nanomaterials

The rampant rise in world population, industrialization, and urbanization expedite the contamination of water sources. The presence of the non-biodegradable character of heavy metals in waterways badly affects the ecological balance. In this modern era, the unavailability of getting clear water as well as the downturn in water quality is a major concern. Therefore, the effective removal of heavy metals has become much more important than before. In recent years, the attention to better wastewater remediation was directed towards adsorption techniques with novel adsorbents such as carbon nanomaterials. This review paper primarily emphasizes the fundamental concepts, structures, and unique surface properties of novel adsorbents, the harmful effects of various heavy metals, and the adsorption mechanism. This review will give an insight into the current status of research in the realm of sustainable wastewater treatment, applications of carbon nanomaterials, different types of functionalized carbon nanotubes, graphene, graphene oxide, and their adsorption capacity. The importance of MD simulations and density functional theory (DFT) in the elimination of heavy metals from aqueous media is also discussed. In addition to that, the effect of factors on heavy metal adsorption such as electric field and pressure is addressed.

Efficient removal of copper and silver ions in electroplating wastewater by magnetic-MOF-based hydrogel and a reuse case for photocatalytic application

Direct discharge of electroplating wastewater containing hazardous metal ions such as Cu2+ and Ag + results in environmental pollution. In this study, we rationally prepare a magnetic composite hydrogel consisted of Fe3O4, UiO-66-NH2, chitosan (CTS) and polyethyleneimine (PEI), namely Fe3O4@UiO-66-NH2/CTS-PEI. Thanks to the strong attraction between the amino group and metal cations, the Fe3O4@UiO-66-NH2/CTS-PEI hydrogel shows the maximum adsorption capacities of 321.67 mg g-1 for Cu2+ ions and 226.88 mg g-1 for Ag + ions within 120 min. As real scenario, the Fe3O4@UiO-66-NH2/CTS-PEI hydrogel exhibits excellent removal efficiencies for metallic ions even in the complicated media of actual electroplating wastewater. In addition, we explore the competitive adsorption order of metal cations by using experimental characterization and theoretical calculations. The optimal configuration of CTS-PEI is also discovered with the density functional theory, and the water retention within hydrogel is simulated through molecular dynamics modeling. We find that the Fe3O4@UiO-66-NH2/CTS-PEI hydrogel could be reused and after 5 cycles of adsorption-desorption, removal efficiency could maintain 80%. Finally, the Ag+ accumulated by hydrogel are reduced to generate a photocatalyst for efficient degradation of Rhodamine B. The novel magnetic hydrogel paves a promising path for efficient removal of heavy metal ions in wastewater and further resource utilization as photocatalysts.

Microwave-assisted one-pot preparation of magnetic cactus-derived hydrochar for efficient removal of lead(Ⅱ) and phenol from water: Performance and mechanism exploration

A novel magnetic hydrochar derived from cactus cladode (MW-MHC) was successfully synthesized through one-pot microwave-assisted process for efficiently removing lead(Pb)(Ⅱ) and phenol. From batch adsorption experiments, MW-MHC possessed the highest uptake amounts for Pb(Ⅱ) and phenol of 139.34 and 175.32 mg/g within 20 and 60 min, respectively. Moreover, the removal of Pb(Ⅱ) and phenol by MW-MHC remained essentially stable under the interference of different co-existing cations, presenting the excellent adaptability of MW-MHC. After three cycles of regeneration experiments, MW-MHC still had preferable adsorption performance and could be easily recycled, indicating its excellent reusability. Significantly, the uptake mechanisms of Pb(Ⅱ) on MW-MHC were regarded as chemical complexation, pore filling, precipitation, and electrostatic attraction. Meanwhile, the phenol uptake might be dominated by π-π interaction and hydrogen bonding. The above consequences revealed that MW-MHC with high removal performance was a promising adsorbent for remediating wastewater containing heavy metals and organics.

From Waste to Resource: Valorization of Lignocellulosic Agri-Food Residues through Engineered Hydrochar and Biochar for Environmental and Clean Energy Applications-A Comprehensive Review

Agri-food residues or by-products have increased their contribution to the global tally of unsustainably generated waste. These residues, characterized by their inherent physicochemical properties and rich in lignocellulosic composition, are progressively being recognized as valuable products that align with the principles of zero waste and circular economy advocated for by different government entities. Consequently, they are utilized as raw materials in other industrial sectors, such as the notable case of environmental remediation. This review highlights the substantial potential of thermochemical valorized agri-food residues, transformed into biochar and hydrochar, as versatile adsorbents in wastewater treatment and as promising alternatives in various environmental and energy-related applications. These materials, with their enhanced properties achieved through tailored engineering techniques, offer competent solutions with cost-effective and satisfactory results in applications in various environmental contexts such as removing pollutants from wastewater or green energy generation. This sustainable approach not only addresses environmental concerns but also paves the way for a more eco-friendly and resource-efficient future, making it an exciting prospect for diverse applications.

Potassium permanganate modification of hydrochar enhances sorption of Pb(II), Cu(II), and Cd(II)

Hydrochars formed by hydrothermal carbonization of hickory wood, bamboo, and wheat straw at 200 °C were modified by potassium permanganate (KMnO4) for the sorption of Pb(II), Cd(II), and Cu(II). The wheat straw hydrochar (WSHyC) modified with 0.2 M KMnO4 resulted in the most promising adsorbent (WSHyC-0.2KMnO4). Characterization of WSHyC and WSHyC-0.2KMnO4 revealed that the modified hydrochar features large specific surface area, rich of surface oxygenic functional groups (OCFG), and a significant amount of MnOx micro-particles. Batch adsorption experiments indicated that the adsorption rate by WSHyC-0.2KMnO4 was faster than for WSHyC, attaining equilibrium after around 5 h. The optimum adsorption capacity (Langmuir) of Pb(II), Cd(II), and Cu(II) by WSHyC-0.2KMnO4 was 189.24, 29.06 and 32.68 mg/g, respectively, 12 ∼ 17 times greater than by WSHyC. The significantly enhanced heavy metal adsorption can be attributable to the increased OCFG and MnOx microparticles on the surface, thereby promoting ion exchange, electrostatic interactions, and complexation mechanisms.

Hydrothermal conversion of biomass to fuels, chemicals and materials: A review holistically connecting product properties and marketable applications

Biomass is a renewable and carbon-neutral resource with good features for producing biofuels, biochemicals, and biomaterials. Among the different technologies developed to date to convert biomass into such commodities, hydrothermal conversion (HC) is a very appealing and sustainable option, affording marketable gaseous (primarily containing H₂, CO, CH₄, and CO₂), liquid (biofuels, aqueous phase carbohydrates, and inorganics), and solid products (energy-dense biofuels (up to 30 MJ/kg) with excellent functionality and strength). Given these prospects, this publication first-time puts together essential information on the HC of lignocellulosic and algal biomasses covering all the steps involved. Particularly, this work reports and comments on the most important properties (e.g., physiochemical and fuel properties) of all these products from a holistic and practical perspective. It also gathers vital information addressing selecting and using different downstream/upgrading processes to convert HC reaction products into marketable biofuels (HHV up to 46 MJ/kg), biochemicals (yield >90 %), and biomaterials (great functionality and surface area up to 3600 m²/g). As a result of this practical vision, this work not only comments on and summarizes the most important properties of these products but also analyzes and discusses present and future applications, establishing an invaluable link between product properties and market needs to push HC technologies transition from the laboratory to the industry. Such a practical and pioneering approach paves the way for the future development, commercialization and industrialization of HC technologies to develop holistic and zero-waste biorefinery processes.

Preparation of cellulose-based porous adsorption materials derived from corn straw for wastewater purification

Various methods have been used to cope with heavy metal ion contamination in wastewater, which caused serious hazards to ecological and human health. Adsorption is one of the most frequent, economical and effective methods for removing these contaminants. Herein, a porous and amino-rich cellulose-based composite adsorbent (PEI-PCS) with anisotropic property was successfully prepared by covalently cross-linking polyethyleneimine on delignified corn straw. Combined with the porosity of straw substrate and the chelating ability of amino group to metal ions, the as-prepared PEI-PCS exhibited universality (various metal ions), rapid adsorption behavior (within 180 min achieve adsorption equilibrium), high adsorption capacity (85.47 mg g^-1 for Cu(II)), and good durability (70 % of adsorption efficiency after 5 cycles). In addition, the adsorption process was conformed to pseudo-second-order dynamics and the Langmuir isotherm models. Lastly, the adsorption mechanism was also elucidated. This study provides a sustainable pathway for the manufacture of efficient biomass-based adsorbents and confirms that functionalized corn straw is a promising material for the treatment of heavy metal ions.

The role of renewable energy consumption on environmental degradation in EU countries: do institutional quality, technological innovation, and GDP matter?

In the face of climate change and environmental degradation, reducing emission of greenhouse gases has become a key factor for environmental sustainability. Therefore, the present research is intended to explore the roles of renewable energy consumption, institutional quality, technological innovation, and GDP on carbon dioxide emissions in the 14 EU countries. In doing so, this study employed novel method of moments quantile regression (MMQR) using annual data from 2000 to 2019. Also, a number of other estimators were applied for robustness check including the fully modified ordinary least square (FMOLS), the dynamic ordinary least squares (DOLS), and the fixed effect ordinary least square (FE-OLS). The empirical findings indicate that renewable energy consumption significantly reduces CO₂ emissions across all quantiles (0.1-0.9). Furthermore, institutional quality and technological innovation improve environmental quality in 0.1-0.7 quantiles, although GDP enhances carbon emissions significantly in all quantiles. In addition, the FMOLS, DOLS, and FE-OLS results confirmed the MMQR results. The outcomes of this study suggest insights for the policymakers to mitigate carbon emissions through promoting innovative technologies for environmental protection and investing more in the development of renewable energy.

Utilization of nano volcanic ash as a natural economical adsorbent for removing cadmium from wastewater

The physical properties of volcanic ashes (pumice and scoria) differ based on the locations and historical conditions of the volcanic eruptions, affecting their utilization in applications. In this study, the effectiveness of nano volcanic ash from Al Jabal Al Abyad in eliminating cadmium from aqueous solutions was investigated. Volcanic ash powder was initially milled using a high-energy ball mill to obtain particles with sizes of approximately 500 and 100 nm that were used as adsorbents. The mineralogical and physicochemical properties of the volcanic ash powder were determined using X-ray fluorescence spectroscopy, X-ray diffraction, Raman spectroscopy, and Barrett-Joyner-Halenda analysis. Then, the characteristics of cadmium adsorption (from an aqueous solution) on the volcanic ash powder and nano volcanic ash were determined using atomic absorption spectrophotometry by varying the solution pH, contact time, and initial metal (Cd) ion concentration. Isothermal adsorption and kinetic models were used to determine the analytical potential of the nano volcanic ash. Based on isothermal adsorption analysis, the adsorption capacity increased from 31 to 166 mg/g at pH 6. The adsorption capacity of volcanic ash was much more efficient than that of other natural absorbents owing to its chemical composition, the production of nanoparticles from powdered volcanic ash, and the increase surface area of the adsorbent from 0.293 m²/g to 20.8735 m²/g. The results showed that the adsorption process occurred mainly via monolayer adsorption on the homogeneous adsorbent surface, indicating the validity of the Langmuir adsorption isotherm model. The kinetic model showed that the adsorption of Cd on nano volcanic ash followed the pseudo-second-order kinetic model. The adsorption capacity results indicated that nano volcanic ash from Al Jabal Al Abyad is an applicable candidate and economical adsorbent for removing heavy metals such as cadmium from industrial wastewaters.

Removal of perfluorooctanoic acid via polyethyleneimine modified graphene oxide: Effects of water matrices and understanding mechanisms

This research aimed to evaluate the adsorption behaviors and mechanisms of perfluorooctanoic acid (PFOA) onto polyethyleneimine modified graphene oxide (GO-PEI) from aqueous solutions. The adsorption capacity was significantly improved by doping polyethyleneimine (PEI) onto graphene oxide (GO). The Brunauer-Emmett-Teller (BET) isotherm model was considered as the best isotherm model in describing the PFOA adsorption onto GO-PEI3 (w_PEI/w_GO = 3). GO-PEI3 exhibited high adsorption capacity (q_e = 368.2 mg/g, calculated from BET isotherm model) and excellent stability. The maximum monolayer amount of PFOA adsorption onto GO-PEI3 (q_m = 231.2 mg/g) was successfully evaluated. The calculated saturated concentration (C_s = 169.9 mg/L) of PFOA on GO-PEI3 closely agrees with its critical micelle concentration (CMC = 157.0 mg/L), suggesting the formation of multilayer hemi-micelles or micelles PFOA structures on the surface of GO-PEI3. PFOA adsorption onto GO-PEI3 was inhibited by several factors including: the presence of humic acid (HA) by competing with the adsorption sites, background salts through the double-layer compression effect, and the competition from soluble ions for the amine or amide functional groups on GO-PEI3. Finally, both the FT-IR and XPS results confirmed that the adsorption of PFOA onto GO-PEI3 was through electrostatic attraction and hydrophobic interaction (physical adsorption), but not chemical adsorption. This work provides fundamental knowledge both in understanding the adsorption behavior through the BET isotherm model and in developing a stable adsorbent for PFOA adsorption. In addition, the findings highlight the potential of PFOA remediation from wastewater systems using GO-PEI in engineering applications.

Polyethyleneimine modified activated carbon for high-efficiency adsorption of copper ion from simulated wastewater

In this study, activated carbon (AC) was chemically activated using sodium hydroxide (NaOH), and polyethyleneimine (PEI) was grafted onto the AC using glutaraldehyde as a cross-linking agent. Then the modified AC was applied to treat water samples containing copper ions (Cu²⁺). Preparation of AC-NaOH@PEI. The grafted AC was characterized, demonstrating that the specific surface area of material decreased from 959.3 to 556.9 m²/g. The ζ-potential changed from -27.2 to 10.4 mV, and the presence of a distinct flocculation on the surface of the AC was observed via scanning electron microscopy. The results demonstrated that PEI was successfully grafted onto the surface of AC. Furthermore, the adsorption results indicated that the Cu²⁺ adsorption capacity of AC-NaOH@PEI was greatly enhanced with increasing PEI loading. The adsorption amount of Cu²⁺ by the grafted AC-NaOH@PEI-200 increased from 20.02 to 47.8 mg/g. In addition, the adsorption of Cu²⁺ by AC-NaOH@PEI was a pH dependent process. At a pH of 6, the maximum removal rate reached 93%. The adsorption process is better described by the Langmuir and quasi-second order adsorption models, signifying that the adsorption of Cu²⁺ on AC@PEI consists of monolayer adsorption and chemisorption. After four adsorption-desorption cycles, AC@PEI exhibited high adsorption capacity for Cu²⁺, indicating that it has good regeneration ability. It is a promising adsorbent material.

Amine-bilayer-functionalized cellulose-chitosan composite hydrogel for the efficient uptake of hazardous metal cations and catalysis in polluted water

Herein, we represent a novel ecofriendly bilayer-amine group incorporated microcrystalline cellulose (MCC)/chitosan (CS) hydrogel, fabricated via integrating polydopamine (PDA) and polyethyleneimine (PEI) for reliable and effective extraction of copper (Cu²⁺), zinc (Zn²⁺), and nickel (Ni²⁺) ions from effluents. Owing to abundant adsorptive sites, the MCC-PDA-PEI/CS-PDA-PEI hydrogel showed excellent Cu²⁺, Zn²⁺, and Ni²⁺ adsorbabilities of ~434.8, ~277.7, and ~261.8 mg/g, respectively, in a single-ion adsorption system with the adsorption kinetics and isotherm complied with pseudo-second-order and Langmuir models, respectively. In a multi-ion adsorption system, hydrogel removes mixed metal cations with slightly higher selectivity for Cu²⁺. In accordance with X-ray photoelectron and Fourier-transform-infrared spectrometric analyses, a plausible binding mechanism of metal cations on the as-prepared hydrogel was proposed by chelation between hydrogel functional groups and metal ions. In the repetitive adsorption/desorption experiments, the hydrogel retained >40% metal ion adsorption and desorption capacities after four cycles. Furthermore, the Cu²⁺-adsorbing hydrogel could serve as a support for the in situ development of Cu nanoparticles, which showed excellent catalytic performance as demonstrated by the transformation of 4-nitrophenol (4-NP) to 4-aminophenol. This work provides a novel ecofriendly, reusable, and highly-efficient adsorbent, as well as a biocatalyst for remediation of heavy metal cations and 4-NP polluted effluents.

Sorption of Pb(II) onto biochar is enhanced through co-sorption of dissolved organic matter

Biochar plays an important role in controlling migration of pollutants in soils. However, little information is available on the interactions between soil-derived dissolved organic matter (DOM), biochar and soluble metal species. The aim of this work was to present the adsorption process of soil DOM by biochar (corn straw biochar produced at 700 °C) and to determine whether co-sorption of DOM would change the affinity for Pb(II). The adsorption rates of biochar and biochar + DOM for Pb(II) were best fitted with a pseudo-second order kinetic model, and the equilibrium adsorption isotherm data agreed well with both the Langmuir and Freundlich models. Adsorption of DOM to biochar reached equilibrium after 15 h with an uptake of 52% of the supplied DOM. We used fluorescence excitation-emission matrices (EEMs) with parallel factor (PARAFAC) analysis to demonstrate that protein-like, fulvic acid-like and humic acid-like substances were the primary constituents of the DOM, which were quenched over time in the presence of biochar. Synchronous fluorescence spectra indicated that the protein-like structures were the predominant fluorescence substances in DOM. Two-dimensional correlation spectroscopy (2D-COS) showed the binding of DOM to biochar resulted in the quenching of fluorescence in the order: protein-like substances > humic-like substances (280 > 355 nm). Data supports the notion that DOM can increase the adsorption capacity of biochar for metal-ions.

Pyrolysis of grape bagasse to produce char for Cu(II) adsorption: a circular economy perspective

Based on cleaner production and circular economy concepts, chars were produced through thermochemical conversion of grape bagasse and then used as adsorbents to uptake Cu(II) from aqueous media since Cu(II) is a common element found in fungicides to treat grapevines. The grape bagasse and char characteristics were investigated through several analytical techniques (TGA, SEM, XRD, FTIR, and BET). Three chars were obtained using different pyrolysis temperatures: 700, 800, and 900 °C. The materials had similar removal percentages and adsorption capacity. The char produced at 700 °C was chosen due to its lower production cost. Studies were conducted on the adsorbent dosage and pH effect, adsorption kinetics, isotherms, and thermodynamics. The most efficient dosage was 1.5 g L-1, and the pH was 5.5. The kinetic study showed that the equilibrium was reached in 60 min and the pseudo-second-order model presents the best fit. After the temperature influence study (25, 35, 45, and 55 °C), it was possible to verify that Cu(II) adsorption through char was favored at 55 °C. The Freundlich model showed the best fit for the experimental data. The highest removal percentage was 96.56%, and the high maximum adsorption capacity was 42 mg g-1. The thermodynamic study shows the adsorption as a spontaneous process, favorable, and endothermic.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13399-022-02792-8.

Influence of sequential HTC pre-treatment and pyrolysis on wet food-industry wastes: Optimisation toward nitrogen-rich hierarchical carbonaceous materials intended for use in energy storage solutions

Due to elevated protein content, the food-industry bio-wastes are promising feedstock to produce hierarchical (micro-mesoporous) carbonaceous materials with the intended use as electrodes in the energy storage solutions. However, the high initial water content, makes their direct activation through high-temperature processes costineffective due to significant heat requirements. In this study, the influence of pretreatment with hydrothermal carbonization (HTC) on wet food-industry bio-wastes, further pyrolysed, was investigated. Selected wastes (brewer's spent grains, spent coffee grains and spent sugar beets) were pre-treated by HTC at 180 °C or 240 °C, and then pyrolysed at 500 °C or 700 °C. Obtained materials were examined using elemental analysis, gas adsorption (N₂ and CO₂) and FT-IR. Besides minor differences caused by the bio-composition of wastes, the general trends were similar for feedstock. The pre-treatment had a beneficial influence on the properties of all wastes. The HTC at 180 °C and pyrolysis at 700 °C for all wastes show the most promising total specific surface area 560 ± 10 m²/g and accessible specific surface area 96 m²/g. Those conditions simultaneously did not reduce the total solid yield in comparison to the one-step process. The pre-treatment at 240 °C led to elevated nitrogen incorporation in the carbonaceous structure compared to HTC at 180 °C. However, it formed a hierarchical structure that was not stable for the thermal treatment. Study proves the HTC pre-treatment at 180 °C is beneficial for the conversion of food-industry bio-wastes into hierarchical carbonaceous material for their use in the energy storage systems application.

Emerging advances and current applications of nanoMOF-based membranes for water treatment

Metal-organic frameworks (MOFs) are significantly tunable materials that can be exploited in a wide range of applications. In recent years, a large number of studies have been focused on synthesizing nano-scale MOFs (nanoMOFs), thus taking advantage of these unique materials in various applications, especially those that are only possible at nano-scale. One of the technologies where nanoMOF materials occupy a central role is the membrane technology as one of the most efficient separation techniques. Therefore, numerous reports can be found on the enhancement of the physicochemical properties of polymeric membranes by using nanoMOFs, leading to remarkably improved performance. One of the most considerable applications of these nanoMOF-based membranes is in water treatment systems, because freshwater scarcity is now an undeniable crisis facing humanity. In this in-depth review, the most prominent synthesis and post-synthesis methods for the fabrication of nanoMOFs are initially discussed. Afterwards, different nanoMOF-based composite membranes such as thin-film nanocomposites (TFN) and mixed-matrix membranes (MMM) and their various fabrication methods are reviewed and compared. Then, the impacts of using MOFs-based membranes for water purification through growing metal-organic frameworks crystals on the support materials and utilization of metal-organic frameworks as fillers in mixed matrix membrane (MMM) are highlighted. Finally, a summary of pros and cons of using nanoMOFs in membrane technology for water treatment purposes and clear future prospects and research potentials are presented.

The dynamics of public spending on sustainable green economy: role of technological innovation and industrial structure effects

In order to achieve the goal of sustainable green economic development, it is necessary to conduct a comprehensive assessment of the efficiency of the green economy and compare it with emission reductions. The green economy idea is a much-discussed solution to economic growth. Therefore, this study investigated the impact of government spending on the performance of the green economy of various countries under the "Belt and Road" (BRI) initiative project. The data were analyzed using the BRI economy panel data from 2008 to 2018. The generalized method of moments (GMM) was used to estimate the effect of government expenditures on education and research and development (R&D) on green economic performance index (GEE) in BRI countries. The results reveal that during the study period, BRI countries have experienced an upward transition towards green development, except for Pakistan and Bangladesh; their GEE decreased gradually from 2010 to 2018. Further, the findings of the system GMM revealed that both education and R&D have a positive impact on the green economy. Moreover, the compositional and technological effects of the overall sample were verified with the GMM process. Nevertheless, the sub-sample results revealed a heterogeneous impact on countries with a high per capita GDP. Following the results, useful policy measures for promoting sustainable green economic development have been proposed.

Adsorption properties and recognition mechanisms of a novel surface imprinted polymer for selective removal of Cu(II)-citrate complexes

Cu(II)-citrate (Cu(II)-CA) complex, as one of the components in plating solutions, increases the difficulty of Cu(II) treatment due to its stable structure and high mobility. In this work, a novel surface imprinted polymer (Cu-CA-SIP) for selective removal of Cu(II)-CA complex from aqueous solution is synthesized by using polyethyleneimine (PEI) grafted onto chloromethylated polystyrene (CMP) microspheres. Cu(II)-CA anions are successfully imprinted with the molar ration of 1:1 by Cu-CA-SIP at initial pH 4.0. Nearly 100% removal rate can be achieved even at low Cu(II)-CA concentration (0.5 mmol/L), and the maximum Cu(II) uptake of Cu-CA-SIP reaches 1.38 mmol/g at 303 K. In Cu(II)/Fe(III)-CA, Cu(II)/Ni(II)-CA, Cu(II)/Zn(II)-CA and Cu(II)/Cd(II)-CA systems, the relative selectivity coefficients of Cu-CA-SIP for Cu(II)-CA are 9.66, 2.32, 1.40 and 44.55, respectively. Moreover, Cu-CA-SIP can be retrieved with negligible loss of adsorption capacity after six times of reuse. The Cu-CA-SIP column can effectively treat the actual electroplating wastewater within 114 BV, and can still reach 104 BV after three dynamic cycles. Therefore, an innovative imprinted material is designed for the first time on the basis of coordination-configuration recognition mechanism for the treatment of electroplating wastewater, providing a new insight in developing surface imprinted polymer in environmental remediation.

Loading with micro-nanosized α-MnO2 efficiently promotes the removal of arsenite and arsenate by biochar derived from maize straw waste: Dual role of deep oxidation and adsorption

The function of biochar (BC) as an eco-friendly adsorbent for environmental remediation is gaining much attention. However, the pristine BC had limited abilities for the removal of As (III, V). Towards this issue, this study synthesized biochar/micro-nanosized α-MnO₂ (BM) composites with different mass ratios of biochar to MnO₂. Comprehensive characterizations confirmed the successful loading of micro-nanosized α-MnO₂ onto the BC surface and the obvious specific surface area enhancement (7.5-13.5 times) of BM relative to BC. BM composites exhibited 5.0-13.0 folds higher removal capacity for As (III, V) than pristine BC since the composites gave full play to the oxidation contributed by micro-nanosized α-MnO₂ substrate and adsorption functions provided by the Mn-OH, BC-COOH, and BC-OH functional groups. Moreover, BM was well reused maintaining a relatively high removal efficiency for As (III, V). Regardless of reaction time and initial As (III) concentration (C₀), the removal of As (III) by pristine BC was negligibly contributed by the oxidized As (V) remaining in solutions, with the relative contribution <15.0%. For the BM composites, relative contribution of adsorbed As (III, V) dominated over that of oxidation to mobile As (V) remaining in solution, and exhibited the decreasing trend with increasing C₀. These findings demonstrated BM as a promising candidate in remediating As (III, V)-polluted water, and provide mechanistic insights into the role of oxidation and adsorption in As (III, V) removal.

Evaluating an economic application of renewable generated hydrogen: A way forward for green economic performance and policy measures

Energy security and environmental measurements are incomplete without renewable energy; therefore, there is a dire need to explore new energy sources. Hence, this study aimed to measure the wind power potential to generate renewable hydrogen (H2), including its production and supply cost. This study used first-order engineering model and net present value to measure the levelized cost of wind-generated renewable hydrogen by using the data source of the Pakistan Meteorological Department and State Bank of Pakistan. Results showed that the use of surplus wind and renewable hydrogen energy for green economic production is suggested as an innovative project option for large-scale hydrogen use. The key annual running expenses for hydrogen are electricity and storage costs, which have a significant impact on the costs of renewable hydrogen. The results also indicated that the project can potentially cut carbon dioxide (CO2) pollution by 139 million metric tons and raise revenue for wind power plants by US$2998.52 million. The renewable electrolyzer plants avoided CO2 at a rate of US$24.9-36.9/ton under baseload service, relative to US$44.3/ton for the benchmark. However, in the more practical mid-load situation, these plants have significant benefits. Further, the wind-generated renewable hydrogen delivers 6-11% larger annual rate of return than the standard CO2 catch plant due to their capacity to remain running and supply hydrogen to the consumer through periods of plentiful wind and heat. Also, the measured levelized output cost of hydrogen (LCOH) was US$6.22/kgH2, and for the PEC system, it was US$8.43/kgH2. Finally, it is a mutually agreed consensus among environmental scientists that the integration of renewable energy is the way forward to increase energy security and environmental performance by ensuring uninterrupted clean and green energy. This application has the potential to address Pakistan's urgent issues of large-scale surplus wind- and solar-generated energy, as well as rising energy demand.

How marine tourism promote financial development in sustainable economy: new evidences from South Asia and implications to future tourism students

The ocean economy and marine tourism policies are global economic concerns being looked at from a deeply holistic viewpoint. For South Asian countries, the ocean economy and marine tourism have successive socio-economic importance. The quantification of the ocean economy and marine tourism also poses some major challenges, and these challenges pose limitations for policymaking by the government and other relevant agencies. The study has used the newly developed hidden panel cointegration test, and the nonlinear panel autoregressive distributed lag (NPARDL) model for a relationship between economic growth and tourism is assessed. This study offers consistent and reliable results of cointegration by incorporating the findings of four approaches to cointegration. The empirical results illustrate the asymmetric relationship between ocean and marine tourism and economic growth. The findings showed that 1% increase in long-term tourism economic growth is adjusted by 2.95% annually. This research paper aims to provide a policy related to South Asia's economic activities and ocean and marine tourism economic significance. Protecting local marine protected areas (MPAs) will improve the economic benefits of the ocean and the marine economy. The policy suggests that there should be a law ensuring that marine tourism is of high quality and environment friendly. This paper provides a guideline for further research with a strong emphasis on ocean- and marine-related economic development and tourism.

Assessment of sustainability and uncertainties of oil markets: mediating determinants of energy use and CO2 emissions

The current paper investigates the sustainability growth problem in the USA and evaluating the co-integration relationship among all variables, including oil, carbon emission, and consumption of energy. We also determine the impacts of energy consumption on the USA economic growth, government spending, and trade openness. We used the co-integration and popular lag model (ARDL) to find the long-term and short-term relationships between all study variables. The empirical results show that (1) the crude oil prices increase and adverse impact on energy demand and government expenditure during the study periods, and CO₂ emission negatively affects USA economic growth. In addition, (2) the innovative accounting method (ICA) results, we used further research to research the causality between study variables. The empirical results propose that oil prices affect the country's economy responsible for more energy consumption, and the causal effect between consumption of energy and economic growth is not relevant. Wastage of energy allows the system to produce more CO₂ emissions. Model results find that the one-sided causal effects of economic growth and CO₂. We see during the analyses that (CO₂) emissions will negatively impact the country's economy. Therefore, country policymakers are expected to change fossil fuel energy to non-fossil fuel energy as an essential component of the USA's economic growth policies.

Assessing the role of financing in sustainable business environment

Speedy economy-wide transition to less carbon-intensive energy generations sources needs extra sizable financing on ground-breaking, nevertheless, risky and less carbon-intensive generation sources. Maximizing the maximum non-government financing needs using the appropriate policy tools, however, fiscal strategies and directives have been thoroughly studied, systematic quantifiable indications about the impacts of government explicit financing is inadequate. We equally give an initial measurable calculation of the impact of government explicit financing on non-government financing into conventional electricity generation sources for 22 OECD nations in the year 2001-2018. Applying FGLS and non-dynamic and non-static GMM regressors, we discover that government financing unilaterally has an explicit and nevertheless reliably the most impacts on non-government financing movements compared to feed-in tariffs (FiTs), taxes, and renewable purchase obligations (RPS) in all and regarding wind and solar sources differently. Ramifications for policy geared towards fast-tracking the energy transition are deliberated. We highlighted those important dedications to scale-up wind and solar energy demands organized by financiers such as asset funding. Furthermore, to arrive at the energy crossover to a carbon-free power system, government and non-government financiers have to continue financing and expand their activities in financing studies, demonstration, and initial scale-up. We reveal that the delivery of government finance is directly correlated with non-government funding movements. Furthermore, we postulate that government policy incentives for non-government financing, nevertheless, have impacts of unconventional energy sources share on non-government financing more than those of FiTs. Ultimately, the supply of conventional fuels is a significant impediment to solar energy financing, while the existence of other sources of cleaner energies promotes non-government climate finance.

Financing for energy efficiency solutions to mitigate opportunity cost of coal consumption: An empirical analysis of Chinese industries

This study measures the energy rebound effects of Chinese energy and coal power use in Chinese energy-intensive industries by using latent class stochastic frontier models like LMDI, and other various econometric estimation approach for coal-supplying regions in China ranging between 1992 and 2018. The findings reveals that China's coal sector's average capacity consumption is 0.81%, with a pattern of first increasing and then decreasing, falling to 0.68% in 2016 specifically. The coal capacity operation rate concerning low as well as depleted regions is generally strong, with limited space for expansion. In 2015 and 2016, the utilization rate of coal production potential in moderate-producing areas fell about 42%. Economic development variables affect the capacity utilization levels of moderate, weak, and depleted generating regions. At the same time, the price volatility cannot induce a practical improvement in the ability utilization rate, which means that China's coal industry is mainly un-marketized. China's energy efficiency increased about 19.98% among 2000 and 2016, while the rapidest expansion pattern has been noted in the eastern province at 39.86%, next to central (11.71%) and western regions (9.59%). The take back impact via the renewable energy and renewable productivity channels is estimated as 12.34% and 25.40%, respectively. Therefore, the take back impact is of significant importance regarding energy preservation, as China's cumulative renewable energy use is equal to China's aggregate energy use. On such findings, recent research also contributed by presenting novel policy implications for key stakeholders.

Assessing the role of financing in sustainable business environment

Speedy economy-wide transition to less carbon-intensive energy generations sources needs extra sizable financing on ground-breaking, nevertheless, risky and less carbon-intensive generation sources. Maximizing the maximum non-government financing needs using the appropriate policy tools, however, fiscal strategies and directives have been thoroughly studied, systematic quantifiable indications about the impacts of government explicit financing is inadequate. We equally give an initial measurable calculation of the impact of government explicit financing on non-government financing into conventional electricity generation sources for 22 OECD nations in the year 2001-2018. Applying FGLS and non-dynamic and non-static GMM regressors, we discover that government financing unilaterally has an explicit and nevertheless reliably the most impacts on non-government financing movements compared to feed-in tariffs (FiTs), taxes, and renewable purchase obligations (RPS) in all and regarding wind and solar sources differently. Ramifications for policy geared towards fast-tracking the energy transition are deliberated. We highlighted those important dedications to scale-up wind and solar energy demands organized by financiers such as asset funding. Furthermore, to arrive at the energy crossover to a carbon-free power system, government and non-government financiers have to continue financing and expand their activities in financing studies, demonstration, and initial scale-up. We reveal that the delivery of government finance is directly correlated with non-government funding movements. Furthermore, we postulate that government policy incentives for non-government financing, nevertheless, have impacts of unconventional energy sources share on non-government financing more than those of FiTs. Ultimately, the supply of conventional fuels is a significant impediment to solar energy financing, while the existence of other sources of cleaner energies promotes non-government climate finance.

How CO2 emissions respond to changes in government size and level of digitalization? Evidence from the BRICS countries

The role of government size and digitization in the process of environmental quality is a matter of considerable debate in the field of environmental economics. BRICS economies have suffered from environmental pollution. This paper scrutinizes that how CO₂ emissions respond to government size and digitization in BRICS economies. Empirical estimates of the ARDL approach show that government size has a positive impact on CO₂ in Brazil, India, and China, while negative impact on CO₂ in Russia in the long run. The long-run estimates reveal a negative and significant effect of digitization on CO₂ in Brazil, India, and China. Education and e-learning activities have a favorable and crucial role played in environmental quality in Brazil, India, and China. Based on these findings, BRICS authorities should improve the efficiency of government expenditures and invest more in digitization to improve the quality of the environment.

Testing role of green financing on climate change mitigation: Evidences from G7 and E7 countries

The study estimates the long-run dynamics of a cleaner environment in promoting the gross domestic product of E7 and G7 countries. The recent study intends to estimate the climate change mitigation factor for a cleaner environment with the GDP of E7 countries and G7 countries from 2010 to 2018. For long-run estimation, second-generation panel data techniques including augmented Dickey-Fuller (ADF), Phillip-Peron technique and fully modified ordinary least square (FMOLS) techniques are applied to draw the long-run inference. The results of the study are robust with VECM technique. The outcomes of the study revealed that climate change mitigation indicators significantly affect the GDP of G7 countries than that of E7 countries. The GDP of both E7 and G7 countries is found depleting due to less clean environment. However, green financing techniques helps to clean the environment and reinforce the confidence of policymakers on the elevation of green economic growth in G7 and E7 countries. Furthermore, study results shown that a 1% rise in green financing index improves the environmental quality by 0.375% in G7 countries, while it purifies 0.3920% environment in E7 countries. There is a need to reduce environmental pollution, shift energy generation sources towards alternative, innovative and green sources.The study also provides different policy implications for the stakeholders guiding to actively promote financial hedging for green financing. So that climate change and envoirnmental pollution reduction could be achieved effectively. The novelty of the study lies in study framework.

Cu(II) and Cd(II) removal from aqueous solution with LDH@GO-NH2 and LDH@GO-SH: kinetics and probable mechanism

Two novel adsorbents (LDH@GO-NH2 and LDH@GO-SH) were successfully synthesized by grafting thiol- or amino-functionalized GO onto LDH and their adsorption capacities for heavy metal ions (Cu(II) and Cd(II)) were significantly enhanced. Characterization experiments illustrated that the thiol group (-SH) or amino group (-NH2) was grafted onto LDH@GO-NH2 or LDH@GO-SH. Adsorption isotherms were satisfactorily fitted by both Langmuir and Freundlich models. The maximum adsorption capacity of Cd(II) on LDH@GO-SH at 308 K was 102.77 mg/g, which was about triple that of LDH@GO-NH2. The enhancement in adsorption capacity of LDH@GO-SH was due to the cooperative effect of LDH and GO-SH. The kinetic experimental data for LDH@GO-NH2 and LDH@GO-SH were found to be in good agreement with the pseudo-second-order model. The thermodynamic parameters calculated from the temperature-dependent adsorption isotherms indicated that the adsorption was spontaneous and an endothermic process. The possible adsorption mechanisms comprising formation of precipitation, isomorphic substitution of Mg(II), and formation of complexation with amino groups or thiol groups were proposed. Desorption experiments put into evidence that LDH@GO-NH2 and LDH@GO-SH may be promising suitable candidates for the remediation of metal ions from aqueous solutions in real work in the near future.

Dynamic effects of fiscal and monetary policy instruments on environmental pollution in ASEAN

This study aims to re-examine the impacts of monetary and fiscal policy on environmental quality in ASEAN countries from 1990 to 2019. We utilized the panel and time series NARDL approach to explore the long-run and short-run estimates at a regional level and country level. ASEAN regional-wise analysis shows that contractionary monetary policy reduces the CO2 emissions, while expansionary monetary policy enhances CO2 emissions in the long run. The long-run coefficient further confirms that expansionary fiscal policy mitigates CO2 emissions in ASEAN. The impact of expansionary monetary and fiscal policy on CO2 emissions is positive and significant, while contractionary monetary and fiscal policy have an insignificant impact on CO2 emissions in the short run. ASEAN country-wise analysis also reported the country-specific estimates for the short and long run. Some policies can redesign in light of these novel findings in ASEAN economies.

The hydrochar activation and biocrude upgrading from hydrothermal treatment of lignocellulosic biomass

The production of hydrochar and biocrude from hydrothermal treatment of lignocellulosic biomass is getting increasing attention, but the quality of hydrochar and biocrude need further improvement before utilization. Many attempts have been carried out on the hydrochar activation and biocrude upgrading. However, different methods play different roles on the property of hydrochar and biocrude, this topic received scant attention in recent review papers. Therefore, the influence of different activation methods on hydrochar property, and the potential application of hydrochar were summarized in this study. Meanwhile, the research progress on biocrude upgrading is reported. Besides, the techno-economic analysis of hydrochar and biocrude from hydrothermal treatment of lignocellulosic biomass are also discussed. Finally, the research needs and future directions on hydrochar activation and biocrude upgrading were proposed. This paper could provide insights for further studies on the utilization of hydrochar and biocrude.

Environmental cost of sustainable development and climate change: can SAARC shift some liability with renewable energy and efficiency?

Sustainable development holds the key not to resolve the problems every nation is facing these days but also for long-lasting effects. In the current era of digital age, each nation wants to achieve sustainable development for their future generations. In addition, environmental sustainability is an imperative module to achieve sustainable development. Hence, the present research work scrutinizes the energy efficiency, CO₂ emission, and renewable energy on the sustainable development of SAARC countries through World Bank sample set from 1995 to 2019. The results infer that CO₂ emissions, renewable energy, energy efficiency, GDP, and FDI show a strong correlation with sustainable development in SAARC counties. Furthermore, renewable energy and energy efficiency have been shown to be reliable instruments for reducing CO₂ emissions and achieving sustainable development in SAARC countries. This research will help policymakers take preventative and constructive actions to achieve sustainable development by reducing CO₂ emissions and uplifting the drivers of sustainable development.

Assessing the capacity of renewable power production for green energy system: a way forward towards zero carbon electrification

Ghana suffers from inadequate power supply due to increasing demand though it is amongst the African nations with the highest access to electricity. This research aims to assess the techno-economic potential of wind and solar energy potential for Ghana's northern part. We employ the Weibull distribution function, levelized cost of energy, and net present cost metrics for the economic study. The wind and solar energy resource's structure generated 72,284 kWh yearly. Both systems were identified to be too expensive if implemented under the current financing conditions in the country. The PV systems generated 38,859 kWh/year, representing 53.76% of the total electricity generated in a year, generating renewable hydrogen in the country. The findings show that sizing and management of renewable plants will fulfill the basic annual cooking demands of the populations, which are 785 kg H₂ in Ghana. The countries' capacity for developing solar hydrogen plants is further suggested by generating new solar hydrogen opportunity charts. Considering the significance of hydrogen energy under the renewable energy output, we recommend using hybrid systems for hydrogen production. The findings reveal which flexibility options are critical in key stages of the energy transition to a 70, 80, 90, and 100% renewable energy system.

A review study on new aspects of biodemulsifiers: Production, features and their application in wastewater treatment

The effluent produced in refineries is in the form of an oil/water emulsion that must be treated. These emulsions are often stable and a suitable method must be used to separate the oil from the emulsion. Recently, biosurfactants or biodemulsifiers have received much attention to reduce the interfacial tension between two liquids. Biodemulsifiers are produced by microorganisms and have several benefits over chemical demulsifiers such as low-toxic, biodegradability, eco-friendly and easy synthesis. They can eliminate two phases by changing the interfacial forces between the water and oil molecules. Biosurfactants are categorized based on the molecular weight of their compounds (low or high molecular weight). Sophorolipids, lipopeptides rhamnolipids, trehalolipids, glycolipid, lipoproteins, lichenysin, surfactin, and polymeric biosurfactants are several types of biosurfactants, which are produced by bacteria or fungi. This review study provides a deep evaluation of biosurfactants in the demulsification process. To this end, different types of biosurfactants, the synthesis method of various biosurfactants using various microorganisms, features of biosurfactants, and the role of biodemulsifiers in the demulsification process are thoroughly discussed. Also, the impact of various efficient factors like pH, microorganism type, temperature, the oil content in the emulsion, and gravity on biodemulsificaion was studied. Finally, the mechanism of the demulsification process was discussed. According to previous studies, rhamnolipid biodemulsifier showed the highest biodemulsification efficiency (100%) in the removal of oil from an emulsion.