Natural deep eutectic solvent (fructose-glycine) functionalized-celite/ polyethylene glycol hydrogel nanocomposite for phosphate adsorption: Statistical analysis.

The increasing usage of phosphate fertilizers for agricultural purposes has led to an augmented level of phosphorus in watercourses negatively impacting the ecosystems and water quality warranting its amputation from polluted water. This article describes the preparation of a novel natural deep eutectic solvent (NADES) functionalized-celite/polyethylene glycol hydrogel nanocomposite (NADES-Cel/PEG HNC) for adsorptive phosphate removal from water. The XRD, FTIR, SEM coupled with EDX spectroscopy, TEM, BET analysis, and pHpzc measurement were used to characterise the prepared material. Central composite design (CCD) in response surface methodology (RSM) was used for experimental design to analyse the individual and combined impact of five operational parameters on equilibrium adsorption capacity (Qe), and evaluate the optimal operating conditions by numerical optimization, which were obtained as: contact time (60 min), adsorbent dosage (1.0 g/L), initial [PO43-] (80 mg/L), initial solution pH (3.5), and temperature (304 K). The adsorption process was best explicated via Langmuir adsorption isotherm with a noteworthy saturation capacity, Qm of 111.80 mg PO43-/g at 298 K, and was favourable (S* = 0.99), feasible (ΔG° = -7.02 kJ/mol), exothermic (ΔH° = -8.39 kJ/mol) and physical in nature. The uptake mechanism largely involved H-bonding, electrostatic interaction, n-π interaction and pore-filling. Uptake kinetics of PO43- was best explicated by pseudo-second order model, and the rate-determining step involved both intraparticle and liquid film diffusion mechanisms. The admirable performance of NADES-Cel/PEG HNC was signified by its competent adsorption efficacy and effectual reusability. The pertinence of the hydrogel nanocomposite for treatment of real wastewater was tested. Hence, NADES-Cel/PEG HNC might prove to be a pragmatic adsorbent for decontamination of PO43- from an aqueous environment.

A review on disposal and utilization of phytoremediation plants containing heavy metals.

The reasonable disposal of plant biomass containing heavy metals (HMs) is a difficult problem for the phytoremediation technology. This review summarizes current literature that introduces various disposal and utilization methods (heat treatment, extraction treatment, microbial treatment, compression landfill, and synthesis of nanomaterials) for phytoremediation plants with HMs. The operation process and technical parameters of each disposal method are different. HMs can migrate and transform in different disposal processes. Some disposal and utilization methods can get some by-products. The main purpose of this paper is to provide reference for technical parameters and characteristics of various disposal and utilization methods, so as to choose and use the appropriate method for the treatment of plant biomass containing HMs after phytoremediation.

A review on control factors of pyrolysis technology for plants containing heavy metals.

The treatment of plants with heavy metals, whether they grow naturally in heavy metal contaminated soil or are used for remediation of heavy metal contaminated soil has attracted increasing attention. Pyrolysis is often used for the disposal of plants with heavy metals because it stabilizes heavy metals effectively and produces biochar. The resulting products of pyrolysis are in the form of solid components (char and ash), liquid components (bio-oil and tar), together with gas components (condensable and non-condensable vapor gas). The metal amount in the char or liquid and gaseous phases can be maximized or minimized via treating a plant feedstock containing heavy metals under different conditions. In addition, the potential risk of biochar produced from plants after pyrolysis becomes a research hotspot in the field of pyrolysis technology of plants containing heavy metals. Herein, we review current literatures that emphasize the influencing factors on the metal content in the biochar, liquid and gaseous phases, as well as the potential risk of biochar.

Effect of the pyrolysis duration and the addition of zeolite powder on the leaching toxicity of copper and cadmium in biochar produced from four different aquatic plants.

The study aimed to determine the biochar yield of four aquatic plants, the leaching toxicity of copper (Cu) and cadmium (Cd) in the biochar, and the stabilization characteristics of the biochar produced under different pyrolysis conditions (at 350 °C for 1, 2, and 3 h and absence/presence of zeolite powder). The results showed that different plant species required a different pyrolysis duration and the presence or absence of zeolite powder. The stabilization of Cu and Cd was significantly affected by the pyrolysis duration and the external materials for different plant species and different types of admixtures. Pyrolysis temperatures over 350 °C for 1 h without zeolite powder generated stable Cu and Cd in goldfish algae (Ceratophyllum demersum L.), foxtail algae (Myriophyllum verticillatum L.), and penny grass (Hydrocotyle vulgaris). Pyrolysis temperatures over 350 °C for 1 h with zeolite powder made Cu and Cd stable in water celery (Oenanthe javanica (Bl.) DC). The addition of zeolite powder during pyrolysis was possible due to the weight reduction efficiency in plants with Cu and Cd. Furthermore, the surface of the biochar with the zeolite powder showed honeycombs and a spongy porous structure. The duration of the pyrolysis had little effect on the honeycomb pore structure.

Enhancer assisted-phytoremediation of mercury-contaminated soils by Oxalis corniculata L., and rhizosphere microorganism distribution of Oxalis corniculata L.

The present study investigated remediation of mercury-contaminated soils using Oxalis corniculata L. combined with various enhancers (sodium thiosulfate, ammonium thiosulfate, ethylenediaminetetraacetic acid and diethylenetriaminepentaacetic acid). The experiment was conducted using Oxalis corniculata seedlings planted in pots containing mercury loaded soils. Investigations included analysis of soil properties, plant growth conditions, ability of the plants to accumulate and extract mercury, and rhizosphere microorganism distribution. The maximal mercury content of the aerial parts and the mercury-translocation ratio of Oxalis corniculata treated with enhancers increased compared to Oxalis corniculata without enhancers. Compared with no enhancers, the theoretical reduction in phytoremediation time was about 50%, 25%, 20% and 21% when Oxalis corniculata was treated with sodium thiosulfate (Na2S2O3), ammonium thiosulfate ((NH4)2S2O3), ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA), respectively. The results indicated that the dominant species in rhizosphere soils varied with different enhancers. However, the evenness of background soils, rhizosphere soils of Oxalis corniculata, Oxalis corniculata treated with Na2S2O3, (NH4)2S2O3, EDTA and DTPA was not largely different at 0.62, 0.61, 0.57, 0.64, 0.61 and 0.63, respectively. These findings demonstrate that Oxalis corniculata treated with Na2S2O3 has the potential to recover and reclaim mercury-contaminated soils in pots.

A review on the emerging conversion technology of cellulose, starch, lignin, protein and other organics from vegetable-fruit-based waste.

A large amount of vegetable-fruit-based waste (VFBW) belonging to agricultural waste is produced around the world every year, imposing a huge burden on the environment and sustainable development. VFBW contains a lot of water and useful organic compounds (e.g., cellulose, minerals, starch, proteins, organic acids, lipids, and soluble sugars). Taking into account the composition characteristics and circular economy of VFBW, many new emerging conversion technologies for the treatment of VFBW (such as hydrothermal gasification, ultrasound-assisted extraction, and synthesis of bioplastics) have been developed. This review summarizes the current literature discussing the technical parameters, process, mechanism, and characteristics of various emerging conversion methods, as well as analyzing the application, environmental impact, and bio-economy of by-products from the conversion process, to facilitate solutions to the key problems of engineering cases using these methods. The shortcomings of the current study and the direction of future research are also highlighted in the review.

Control strategies for microplastic pollution in groundwater.

Groundwater is the primary source of water that occurs below the earth's surface. However, the advancement in technology and the increasing population, which lead to the discharge of contaminants such as microplastics (MPs), have an adverse impact on the quality of groundwater. MPs are ubiquitous pollutants that are widely found throughout the world. The maximum abundance of MPs is 4 items/L and 15.2 items/L in groundwater at the specific location of China and USA. Various factors can affect the migration of MPs from soil to groundwater. The occurrence of MPs in water causes serious health issues. Therefore, taking appropriate strategies to control MP contamination in groundwater is urgent and important. This review summarizes the current literature on the migration process of MPs from soil to groundwater along with possible methods for the remediation of MP-polluted groundwater. The main objective of the review is to summarize the technical parameters, process, mechanism, and characteristics of various remediation methods and to analyze strategies for controlling MP pollution in groundwater, providing a reference for future research. Possible control strategies for MP pollution in groundwater include two aspects: i) prevention of MPs from entering groundwater; ii) remediation of polluted groundwater with MPs (ectopic remediation and in-situ remediation). Formulating legislative measures, strengthening public awareness and producing more environment-friendly alternatives can be helpful to reduce the production of MPs from the source. Manage plastic waste reasonably is also a good strategy and the most important part of the management is recycling. The shortcomings of the current study and the direction of future research are also highlighted in the review.

A review on the treatment of dyes in printing and dyeing wastewater by plant biomass carbon.

Printing and dyeing wastewater (PDW) has characteristics of large amount of water, elevated content of residual dyes, poor biodegradability, high alkalinity and large change of water quality, making its treatment difficult. Development of efficient and economic PDW treatment technology has gained considerable interest in the field of environmental protection. Use of plant biomass carbon (PBC) for the adsorption of dyes is a feasible and economical technology. This review summarizes current literature discussing the preparation method and physicochemical characteristics of PBC prepared from different plant species, the effect of PBC on the removal of dyes, influencing factors affecting the removal, and relevant adsorption models. The shortcomings of current research and the direction of future research are also pointed out in the review.

The existence, spread, and strategies for environmental monitoring and control of SARS-CoV-2 in environmental media.

Coronavirus disease 2019 (COVID-19) is the most influential infectious disease to emerge in the early 21st century. The outbreak of COVID-19 has caused a great many deaths and has had a negative impact on the world's economic development. The etiological agent of COVID-19 is severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). SARS-CoV-2, which is highly infectious and variable, can be transmitted through different environmental media (gaseous, liquid, and solid). There are many unanswered questions surrounding this virus. This review summarizes the current knowledge on the latest global COVID-19 epidemic situation, SARS-CoV-2 variants, the progress in SARS-CoV-2 vaccine use, and the existence and spread of SARS-CoV-2 in gaseous, liquid, and solid media, with particular emphasis on the prevention and control of further spread of the disease. This review aims to help people worldwide to become more familiar with the transmission characteristics of SARS-CoV-2 in environmental media, so as targeted measures to fight the epidemic, reduce deaths, and restore the economy can be implemented under the pressure of global SARS-CoV-2 vaccine shortages.

A review on phytoremediation of mercury contaminated soils.

Mercury (Hg) and its compounds are one of the most dangerous environmental pollutants and Hg pollution exists in soils in different degrees over the world. Phytoremediation of Hg-contaminated soils has attracted increasing attention for the advantages of low investment, in-situ remediation, potential economic benefits and so on. Searching for the hyperaccumulator of Hg and its application in practice become a research hotspot. In this context, we review the current literatures that introduce various experimental plant species for accumulating Hg and aided techniques improving the phytoremediation of Hg-contaminated soils. Experimental plant species for accumulating Hg and accumulation or translocation factor of Hg are listed in detail. The translocation factor (TF) is greater than 1.0 for some plant species, however, the bioaccumulation factor (BAF) is greater than 1.0 for Axonopus compressus only. Plant species, soil properties, weather condition, and the bioavailability and heterogeneity of Hg in soils are the main factors affecting the phytoremediation of Hg-contaminated soils. Chemical accelerator kinds and promoting effect of chemical accelerators for accumulating and transferring Hg by various plant species are also discussed. Potassium iodide, compost, ammonium sulphate, ammonium thiosulfate, sodium sulfite, sodium thiosulfate, hydrochloric acid and sulfur fertilizer may be selected to promote the absorption of Hg by plants. The review introduces transgenic gene kinds and promoting effect of transgenic plants for accumulating and transferring Hg in detail. Some transgenic plants can accumulate more Hg than non-transgenic plants. The composition of rhizosphere microorganisms of remediation plants and the effect of rhizosphere microorganisms on the phytoremediation of Hg-contaminated soils are also introduced. Some rhizosphere microorganisms can increase the mobility of Hg in soils and are beneficial for the phytoremediation.

Toxicity assessment of artificially added zinc, selenium, and strontium in water.

The present research was to study the toxicology of artificially added Zn, Se and Sr in water. Specifically, we investigated the mortality and liver toxicity in zebrafish (Danio rerio), caused by different water concentrations of zinc sulfate (ZnSO4), sodium selenite (Na2SeO3), and strontium chloride hexahydrate (6H2O·SrCl2). Adult and embryo-larval zebrafish were used in the experiment. Analysis was performed of mortality, liver area and impermeability, delayed absorption area of the yolk sac, and liver tissue structure. The concentration change of sodium selenite exerted the most significant effect on the mortality of adult zebrafish, followed by that of strontium chloride hexahydrate, and zinc sulfate. Elevated strontium chloride hexahydrate concentration was associated with liver toxicity in zebrafish in the preliminary experiment. However, embryo-larval zebrafish were observed to die when the concentration of Zn2+ or Se4+ increased to a certain extent, without obvious liver toxicity. Our results indicated strontium chloride hexahydrate was hepatotoxic to embryo-larval zebrafish, which was manifested mainly as hepatomegaly and delayed absorption of the yolk sac. In addition, the artificially added strontium chloride hexahydrate destroyed liver tissue structure, resulting in hepatocyte enlargement, cell nucleus enlargement, blurred cytoplasmic boundaries, and formation of a vacuolar liver. These findings suggest the amount of strontium chloride hexahydrate added in soft drinks should be limited to certain levels.

Effect of mixed solutions of heavy metal eluents on soil fertility and microorganisms.

This study analyzed the effect of heavy metal eluents (0.3 mol/L C6H8O7, 5 × 10-4 mol/L EDTA, and 0.01 mol/L Na2S2O3) on the content of organic matter, hydrolytic nitrogen, available phosphorus and potassium, and species composition of bacteria and fungi in vegetable soils. The obtained results documented that the treatment of the soil, consisting of shaking the sample with a mixture of eluents, significantly increased the content of organic matter, hydrolytic nitrogen, and available phosphorus and potassium. The mixed solutions of eluents increase the maximum available P in the soil by 279.3%, and hydrolytic N by 30.7%. The eluents affected, to a certain extent, the dominant species of microorganisms in the soil, but did not increase species richness and evenness in all soil samples.

Effects of growth agents and mercury on several herbs.

The paper discussed the effects of growth agents and mercury on the growth of four herb species subjected to a pot experiment: Aloe vera, Setcreasea purpurea, Chlorophytum comosum, and Oxalis corniculata. We determined the height and biomass production of selected plants treated with different growth agents and different concentrations of mercury solutions. We evaluated the relative growth rate (RGR) of the experimental plants. The aim of the study was to explore potential novel solutions to the shortcoming of the low speed of phytoremediation. The results showed that the upper parts of Aloe vera and Chlorophytum comosum had the fastest growth in the treatment with water only. In contrast, the upper parts of Setcreasea purpurea grew most intensely after the treatment with Lvyebao Fertilizer, whereas the aboveground parts of Oxalis corniculata had the fastest growth after the application of water and the occasional use of Green Cake Fertilizer. In addition, the tolerance to mercury of Oxalis corniculata was the strongest, whereas that of Chlorophytum comosum was the lowest among the species investigated.