Green Remediation Research Articles

Development of novel persulfate tablets for passive trichloroethylene (TCE)-contaminated groundwater remediation

In this study, a biodegradable binder, hydroxypropyl methyl cellulose (HPMC), was used for the first time to mix with persulfate powder for developing novel persulfate-releasing tablets to remediate trichloroethylene (TCE)-contaminated groundwater. To obtain feasible parameters for the preparation of persulfate tablets, different pressures, HPMC/tablet mass ratios, and persulfate dosages were evaluated. The results showed that the persulfate tablet released 2868 mg-persulfate/day for 12 days under the optimal manufacturing parameters of HPMC/tablet mass ratio of 0.5 and pressure of 4.90 × 108 N/m2. Persulfate diffusion and gel layer erosion were dominant mechanisms for controlling the persulfate released in water. The persulfate release time and rate can be controlled by adjusting the persulfate dosage at the optimal HPMC/tablet ratio. In the column experiment, TCE with an initial concentration of 70 mg/L reached 55% removal efficiency by the tablet, which showed that the developed tablet was capable of degrading highly concentrated TCE. The results of electron spin resonance (ESR) spectroscopy showed that both SO4−· and ·OH were responsible for the oxidation of TCE. During 150 days of incubation, the biodegrading efficiency of HPMC by microbes in soil and activated sludge was 67% and 80%, respectively, under aerobic conditions, while 58% of HPMC was removed by soil bacteria under anaerobic conditions. The results showed that persulfate tablets could be used as a passive groundwater remediation system. There is no waste generated after persulfate is completely released during groundwater remediation. The developed persulfate tablets are environmentally friendly and meet the green remediation aspect.

Biodegradation of hazardous naphthalene and cleaner production of rhamnolipids — Green approaches of pollution mitigation

Toxic and hazardous waste poses a serious threat to human health and the environment. Green remediation technologies are required to manage such waste materials, which is a demanding and difficult task. Here, effort was made to explore the role of Pseudomonas aeruginosa SR17 in alleviating naphthalene via catabolism and simultaneously producing biosurfactant. The results showed up to 89.2% naphthalene degradation at 35 °C and pH 7. The GC/MS analysis revealed the generation of naphthalene degradation intermediates. Biosurfactant production led to the reduction of surface tension of the culture medium to 34.5 mN/m. The biosurfactant was further characterized as rhamnolipids. LC-MS of the column purified biosurfactant revealed the presence of both mono and di rhamnolipid congeners. Rhamnolipid find tremendous application in medical field and as well as in detergent industry and since they are of biological origin, they can be used as favorable alternative against their chemical counterparts. The study demonstrated that catabolism of naphthalene and concurrent formation of rhamnolipid can result in a dual activity process, namely environmental cleanup and production of a valuable microbial metabolite. Additionally, the present-day application of rhamnolipids is highlighted.

Soil Remediation: Towards a Resilient and Adaptive Approach to Deal with the Ever-Changing Environmental Challenges

Pollution from numerous contaminants due to many anthropogenic activities affects soils quality. Industrialized countries have many contaminated sites; their remediation is a priority in environmental legislation. The aim of this overview is to consider the evolution of soil remediation from consolidated invasive technologies to environmentally friendly green strategies. The selection of technology is no longer exclusively based on eliminating the source of pollution but aims at remediation, which includes the recovery of soil quality. “Green remediation” appears to be the key to addressing the issue of remediation of contaminated sites as it focuses on environmental quality, including the preservation of the environment. Further developments in green remediation reflect the aim of promoting clean-up strategies that also address the effects of climate change. Sustainable and resilient remediation faces the environmental challenge of achieving targets while reducing the environmental damage caused by clean-up interventions and must involve an awareness that social systems and environmental systems are closely connected.

Natural Siderite Derivatives Activated Peroxydisulfate Toward Oxidation of Organic Contaminant: A Green Soil Remediation Strategy

Natural Siderite Derivatives Activated Peroxydisulfate Toward Oxidation of Organic Contaminant: A Green Soil Remediation Strategy

Natural Siderite Derivatives Activated Peroxydisulfate Toward Oxidation of Organic Contaminant: A Green Soil Remediation Strategy

Natural Siderite Derivatives Activated Peroxydisulfate Toward Oxidation of Organic Contaminant: A Green Soil Remediation Strategy

Natural Siderite Derivatives Activated Peroxydisulfate Toward Oxidation of Organic Contaminant: A Green Soil Remediation Strategy

Natural Siderite Derivatives Activated Peroxydisulfate Toward Oxidation of Organic Contaminant: A Green Soil Remediation Strategy

Response of chlorinated hydrocarbon transformation and microbial community structure in an aquifer to joint H2 and O2.

Hydrogen (H2) and oxygen (O2) are critical electron donors and acceptors to promote the anaerobic and aerobic microbial transformation of chlorinated hydrocarbons (CHCs), respectively. Electrochemical technology can effectively supply H2 and O2 directly to an aquifer. However, the response of CHC transformation and microbial community structure to joint H2 and O2 are still unclear. In this work, microcosms containing different combinations of H2 and O2 were constructed with natural sediments and nine mixed CHCs. The joint H2 and O2 microcosm (H2/O2 microcosm) significantly promoted the biotransformation of trichloroethylene (TCE), trans-dichloroethene (tDCE) and chloroform (CF). Illumina sequencing analyses suggested that a particular microbial community was formed in the H2/O2 microcosm. The specific microbial species included Methyloversatilis, Dechloromonas, Sediminibacterium, Pseudomonas, Acinetobacter, Curvibacter, Comamonas and Acidovorax, and the relative abundance of the tceA, phe and soxB genes synchronously increased. These results suggested that some specific microbes are potential CHC converters using H2 and O2 as energy sources, and aerobic and anaerobic transformations exist simultaneously in the H2/O2 microcosm. It provides a theoretical basis for establishing efficient green remediation technologies for CHC contaminated aquifers.

A review on green remediation techniques for hydrocarbons and heavy metals contaminated soil

Organic pollutants cause many environmental problems to our environment because of their toxicity, non-degradation and ability to long-range transport. The most common organic pollutants are known as persistent organic pollutants (POPs) and are known as hydrocarbons. Effective techniques for the removal of hydrocarbons and heavy metals from soil have drawn great attention. Remediation techniques represent one of the most important of these techniques because of their gentle impact on the environment. The study highlights numerous methods for Physical and chemical remediation techniques with explanation of the ability of some plants and agricultural wastes for remediation.

Selenium treated foliage and biochar treated soil for improved lettuce (Lactuca sativa L.) growth in Cd-polluted soil

Cadmium (Cd) pollution in farmland soils is a serious concern due to its devastating effects on living organisms. This requires developing effective strategies to inhibit the Cd absorption and accumulation by vegetables. In this study, the influence of soil applied biochar (BC) (10 and 30 g kg−1) and foliage applied selenium (Se) fertilizer (1 and 3 mg L−1) on the absorption and accumulation of Cd and growth of lettuce under Cd stress (1 and 3 mg/kg) was evaluated. In Cd-contaminated soil, the application of BC and Se significantly increased lettuce biomass and chlorophyll contents by 74% and 100%, respectively, compared to control in lettuce. The combined application of BC and Se at (B 30 g kg−1, Se 3 mg L−1) was effective in reducing the accumulation of Cd by lettuce shoot by 73.41% than control. Co-application of BC and Se enhanced the activities of antioxidant enzymes catalase, superoxide dismutase by 77 and 96%, respectively, and reduced the malondialdehyde contents by 56% than control. Application of biochar (30 g kg−1) significantly increased the soil electrical conductivity and soil organic carbon of soil by 48 and 41%, respectively as compared to control. The combination of BC and Se (B 30 g kg−1, Se 3 mg L−1) reduced the Cd contents in lettuce shoots from 0.79 mg kg−1 to 0.08 mg kg−1 below the national food safety standard threshold (0.2 mg kg−1 Cd). Overall, this study revealed that the integrated application of BC (30 g kg−1) and Se (3 mg L−1) can help prevent the absorption of Cd by lettuce. However, the effectiveness of BC in remediating trace metals may decrease with time due to the aging factor and leaching alkalinity of BC, so long-term field experiments are needed to enhance the understanding of BC efficiency and an appropriate Se concentration for specific green soil remediation goals.

Application of EPR Spectroscopy in TiO2 and Nb2O5 Photocatalysis

The interaction of light with semiconducting materials becomes the center of a wide range of technologies, such as photocatalysis. This technology has recently attracted increasing attention due to its prospective uses in green energy and environmental remediation. The characterization of the electronic structure of the semiconductors is essential to a deep understanding of the photocatalytic process since they influence and govern the photocatalytic activity by the formation of reactive radical species. Electron paramagnetic resonance (EPR) spectroscopy is a unique analytical tool that can be employed to monitor the photoinduced phenomena occurring in the solid and liquid phases and provides precise insights into the dynamic and reactivity of the photocatalyst under different experimental conditions. This review focus on the application of EPR in the observation of paramagnetic centers formed upon irradiation of titanium dioxide and niobium oxide photocatalysts. TiO2 and Nb2O5 are very well-known semiconductors that have been widely used for photocatalytic applications. A large number of experimental results on both materials offer a reliable platform to illustrate the contribution of the EPR studies on heterogeneous photocatalysis, particularly in monitoring the photogenerated charge carriers, trap states, and surface charge transfer steps. A detailed overview of EPR-spin trapping techniques in mechanistic studies to follow the nature of the photogenerated species in suspension during the photocatalytic process is presented. The role of the electron donors or the electron acceptors and their effect on the photocatalytic process in the solid or the liquid phase are highlighted.

Bioprospecting of indigenous biosurfactant-producing oleophilic bacteria for green remediation: an eco-sustainable approach for the management of petroleum contaminated soil.

In the present study, the efficiency of four different strains of Pseudomonas aeruginosa and their biosurfactants in the bioremediation process were investigated. The strains were found to be capable of metabolizing a wide range of hydrocarbons (HCs) with preference for high molecular weight aliphatic (ALP) over aromatic (ARO) compounds. After treating with individual bacteria and 11 different consortia, the residual crude oils were quantified and qualitatively analyzed. The bacterial strains degraded ALP, ARO, and nitrogen, sulphur, oxygen (NSO) containing fractions of the crude oil by 73-67.5, 31.8-12.3 and 14.7-7.3%, respectively. Additionally, the viscosity of the residual crude oil reduced from 48.7 to 34.6-39mPas. Further, consortium designated as 7 and 11 improved the degradation of ALP, ARO, and NSO HCs portions by 80.4-78.6, 42.7-42.4 and 21.6-19.2%, respectively. Moreover, addition of biosurfactant further increased the degradation performance of consortia by 81.6-80.7, 43.8-42.6 and 22.5-20.7%, respectively. Gas chromatographic analysis confirmed the ability of the individual strains and their consortium to degrade various fractions of crude oil. Experiments with biosurfactants revealed that polyaromatic hydrocarbons (PAHs) are more soluble in the presence of biosurfactants. Phenanthrene had the highest solubility among the tested PAHs, which further increased as biosurfactant doses raised above their respective critical micelle concentrations (CMC). Furthermore, biosurfactants were able to recover 73.5-63.4% of residual oil from the sludge within their respective CMCs. Hence, selected surfactant-producing bacteria and their consortium could be useful in developing a greener and eco-sustainable way for removing crude oil pollutants from soil.

The combination of biochar and PGPBs stimulates the differentiation in rhizosphere soil microbiome and metabolites to suppress soil‐borne pathogens under consecutive monoculture regimes

AbstractThe application of biochar and plant‐growth‐promoting bacteria (PGPBs) in biocontrol soil‐borne pathogens has garnered worldwide interest recently. However, how agricultural replanting disease is alleviated by a combination of biochar and PGPBs treatment (SYBB) remains largely unexplored. In this study, we investigated the beneficial effects of single biochar addition and the combination of biochar and PGPBs on alleviating replanting disease by altering the rhizosphere microbiome and metabolites. Our field experiment showed that the SYBB treatment had a better alleviating effect on replanting disease than the single biochar addition. The study indicated the dominant effect of deterministic processes on the bacterial community and of stochastic processes on the fungal community under biochar and PGPBs treatment. The combination of biochar and PGPBs tended to convert the stochastic processes of fungal community assembly into deterministic processes. We found SYBB treatment increased the abundance of potentially beneficial Pseudomonas, Lysobacter, Gemmatimonadetes and Nitrospira, and decreasing the abundance of potentially pathogenic Fusarium, Talaromyces and Fusarium oxysporum. Moreover, the SYBB treatment increased the abundances of carbohydrates, fatty acids and plant hormones, and decreased the abundances of amino acids in the rhizosphere soil. Co‐occurrence network analysis indicated that SYBB treatment increased the connections within the microbial communities and drove the alteration of co‐occurrence network among the microbial communities and metabolites, which increased positive correlations in bacteria‐metabolite networks and decreased positive correlations in fungi‐metabolite networks. Spearman correlation analysis showed the abundances of beneficial Streptomyces, Pseudomonas and Lysobacter were significantly and positively correlated to the metabolites most increased under SYBB treatment. The combination of biochar and PGPBs alleviated replanting disease by mediating the change of rhizosphere soil metabolites, and stimulating the proliferation of indigenous and beneficial soil microbes. The research results are intended to provide the basis for new strategies for green and sustainable remediation of soil‐borne pathogens.

Speciation, transportation, and pathways of cadmium in soil-rice systems: A review on the environmental implications and remediation approaches for food safety.

Cadmium (Cd) contamination in paddy fields is a serious health concern because of its high toxicity and widespread pollution. Recently, much progress has been made in elucidating the mechanisms involved in Cd uptake, transport, and transformation from paddy soils to rice grains, aiming to mitigate the associated health risk; however, these topics have not been critically reviewed to date. Here, we summarized and reviewed the (1) geochemical distribution and speciation of Cd in soil-rice systems, (2) mobilization, uptake, and transport of Cd from soil to rice grains and the associated health risks, (3) pathways and transformation mechanisms of Cd from soil to rice grains, (4) transporters involved in reducing Cd uptake, transport, and accumulation in rice plants, (5) factors governing Cd bioavailability in paddy, and (6) comparison of remediation approaches for mitigating the environmental and health risks of Cd contamination in paddy fields. Briefly, this review presents the state of the art about the fate of Cd in paddy fields and its transport from soil to grains, contributing to a better understanding of the environmental hazards of Cd in rice ecosystems. Challenges and perspectives for controlling Cd risks in rice are thus raised. The summarized findings in this review may help to develop innovative and applicable methods for controlling Cd accumulation in rice grains and sustainably manage Cd-contaminated paddy fields.

Green remediation of the potential hazardous shellfish wastes generated from the processing industries and their bioprospecting

Shellfish processing is vital for the extraction of crustacean meat in the seafood market. Their processing results in shellfish wastes containing high-value products like chitin. The common method for chitin recovery practised globally utilizes harsh chemicals like HCl and NaOH, for the demineralization and deproteination of the shellfish wastes, releasing harmful acidic and basic effluents as flow through. Recently, mathematical and computational tools are employed to monitor and regulate the concentration of chemical effluents being released from the chitin/chitosan industries. As an alternate measure to prevent the disposal of effluents, greener remediation measures have been preferred for the recovery of chitin. The current paper discusses the harmful effects of the wastes generated by seafood processing and chitin/chitosan industries by chemical methods and suggests a guideline on alternate green environmentally friendly methods like microbial fermentation, application of enzymes, Natural Deep Eutectic Solvents (NADES) etc. for the production of high-quality chitin and other chemical-free protein hydrolysates and their bioprospecting. • Wastes released by seafood processing and chitin and chitosan industries. • Overview of harmful effects of shell wastes and processing effluents. • Strategies for green remediation of wastes and their bioprospecting.

Degradation mechanism and QSAR models of antibiotic contaminants in soil by MgFe-LDH engineered biochar activating urea-hydrogen peroxide

Developing an in-situ soil remediation technology for simultaneous catalytic degradation of contaminants and nitrogen supplementation is of great importance but remains challenging. Herein, MgFe-LDH engineered biochar (MB) was successfully synthesized by using a simple co-precipitation method. The as-prepared materials were used as catalysts for the first time to activate urea-hydrogen peroxide (UHP) to degrade antibiotic sulfamethoxazole (SMX) and provide nitrogen. The enhanced degradation efficiency of SMX (91%) were mainly attributed to •OH and 1O2-mediated oxidation. Pot experiments showed MB/UHP significantly decreased the SMX concentration from 6.47 to 2.10 mg kg−1 and simultaneously increased NH4+-N and NO3--N concentration. The optimal quantitative-structure-activity-relationship model for 19 antibiotics suggested the dipole moment, energy of the highest occupied molecular orbital, and bond order were the intrinsic influencing factors. This study not only provides a green remediation technology but also offers a theoretical basis for estimating the removal rate of unexplored antibiotics.

A Questionnaire Survey on Contaminated Site Regulators’ View of Implementing Green and Sustainable Remediation in China

Government contaminated site regulators, as policy executors and makers, have a profound impact on the development of green and sustainable remediation (GSR), but their cognitive level of GSR has not been well-studied. China has some experience in the management of contaminated sites and has the foundation to promote GSR. This study was conducted in the form of a questionnaire to investigate the understanding of GSR among Chinese site regulators at different levels. The study found that there was still a lot of resistance to promoting GSR in China. Firstly, even though the regulators thought GSR was necessary in China, most of them did not know GSR very well or lacked practical experience. Secondly, existing national and provincial policy standards did not have a good balance between the environmental, social and economic aspects, but gave priority to the environmental factors. Thirdly, the lack of standard and regulatory requirements was the most significant barrier to the implementation of GSR. The results of the survey can provide a reference for China or other developing countries to implement GSR. Practitioners should provide more knowledge and cases for regulators, supplement national policies or improve the provincial and municipal policy system.

Interplay of bicarbonate and the oxygen-containing groups of carbon nanotubes dominated the metal-free activation of peroxymonosulfate

Revealing how different physicochemical/texture properties and water matrices affect the carbocatalysis-based oxidation processes (COPs) is critical to develop green remediation methods for wastewater detoxification. However, the interplay of oxygen-containing groups (OCGs) of carbocatalysts and alkalinity on the oxidation behavior of organic pollutants by COPs is rarely documented. In this study, we investigated the mutual effects of OCGs and bicarbonate on the catalytic activation of Peroxymonosulfate (PMS) by carbon nanotubes (CNTs) with respect to the formation of Reactive oxygen species (ROS) and oxidation behavior of ibuprofen. The profiles of the removal kinetics of ibuprofen, degradation products, and product toxicity highly rely on the OCGs and bicarbonate-regulated ROS. The CO groups within CNTs serve as an electron donor to cleave the OO bond of PMS for producing •OH. Increasing the amount of electron-rich CO/COH groups can induce the formation of SO4•−. The electron-rich OCGs deprotonated by bicarbonate promote the PMS activation/decomposition to generate more •OH and/or SO4•−, while the deprotonated electron-deficient OCGs can activate PMS to form 1O2. The HCO3−/CO32− in the bicarbonate-containing CNTs/PMS system can partially quench •OH and SO4•− to produce CO3•−. Despite the diverse ROS controlled by OCGs and bicarbonate, •OH and/or SO4•−-initiated H-atom abstraction reactions are the first steps for the degradation of target contaminant.

Groundwater remediation using Magnesium–Aluminum alloys and in situ layered doubled hydroxides

In situ remediation of groundwater by zerovalent iron (ZVI)-based technology faces the problems of rapid passivation, fast agglomeration, limited range of pollutants and secondary contamination. Here a new concept of Magnesium-Aluminum (Mg-Al) alloys and in situ layered double hydroxides on is proposed for the degradation and removal of a wide variety of inorganic and organic pollutants from groundwater. The Mg-Al alloy provides the electrons for the chemical reduction and/or the degradation of pollutants while released Mg2+, Al3+ and OH- ions react to generate in situ LDH precipitates, incorporating other divalent and trivalent metals and oxyanions pollutants and further adsorbing the micropollutants. The Mg-Al alloy outperforms ZVI for treating acidic, synthetic groundwater samples contaminated by complex chemical mixtures of heavy metals (Cd2+, Cr6+, Cu2+, Ni2+ and Zn2+), nitrate, AsO33-, methyl blue, trichloroacetic acid and glyphosate. Specifically, the Mg-Al alloy achieves removal efficiency ≥99.7% for these multiple pollutants at concentrations ranging between 10 and 50mgL-1 without producing any secondary contaminants. In contrast, ZVI removal efficiency did not exceed 90% and secondary contamination up to 220mgL-1 Fe was observed. Overall, this study provides a new alternative approach to develop efficient, cost-effective and green remediation for water and groundwater.

Atmospheric plasma-based approaches for the degradation of dimethyl phthalate (DMP) in water

Cold plasma based treatment of contaminated water is becoming a promising novel green remediation option. This study assessed the performance of two different cold plasma reactors, using, respectively, a self-pulsing discharge (SPD) and a multipin corona discharge (MCD), in the degradation of dimethyl phthalate (DMP), a persistent and ubiquitous pollutant of the aquatic environment. The process kinetics and energy efficiency, as well as the main plasma generated reactive species were determined under various operating conditions concerning the plasma feed gas and flowrate, the voltage polarity, the input power, the DMP initial concentration, the liquid conductivity, and the aqueous matrix used to prepare DMP solutions for these experiments. The MCD reactor, operated with air as plasma feed gas and negative voltage polarity, gave the best results in terms of rate and energy efficiency. Moreover, variations in plasma input power and in the liquid conductivity have limited effect on DMP degradation rate, making this reactor suitable for treating liquids with a range of initial conductivities The effects of DMP initial concentration on its rate of degradation and on the process energy efficiency were also investigated. Differences in the efficiency of production and distribution of plasma generated reactive species, notably •OH and H2O2, observed for the two tested reactors are discussed in terms of different extension of the plasma/liquid interface and diffusion into the bulk solution. It is proposed that among the reactive species, •OH foremost, and O3 to a lesser extent, play a pivotal role in DMP degradation, while the contribution of H2O2 appears to be limited. The rate of DMP degradation was not drastically different in Milli-Q water and in tap water, a positive outcome in view of practical applications of the technology. The lower rate observed in tap than in Milli-Q water is attributed to the presence of bicarbonate and carbonate, which are known scavengers of hydroxyl radicals.

Green remediation of high-lead contaminated soil by stabilization/solidification with insoluble humin: Long-term leaching and mechanical characteristics

High concentrations of lead in soil will greatly weaken the stabilization/solidification effect. Humin (HM) is expected to improve this process because it is a neutral, insoluble, porous and green material as well as an eco-friendly adsorbent extracted from natural peat soil. However, HM has not been studied with respect to the stabilization/solidification (S/S) characteristics of potentially toxic element (PTE)-contaminated soil due to its different extraction sources and methods, as well as complex properties. To study these effects, insoluble HM was extracted for treatment of high-lead contaminated soil by cement-based S/S. The experimental results show that HM has a strong adsorption capacity for lead with a maximum adsorption capacity of 200.2 mg kg−1. The negative influence of a high content of lead on the compressive strength over a 0–90-day period is weakened after adding HM to the soil, wherein a competitive mechanism between HM and a high concentration of lead is proposed. The lead leaching concentration of stabilized soil is significantly decreased under different leaching methods from 0 to 60 days and then decreases slowly. The lead speciation results for the stabilized soil determined through the Tessier sequential extraction method show that HM promotes the gradual chemical transformation of lead from exchangeable and carbonate-bound fractions to a more stable state, with respective decreases of 27.5% and 15.1%. In addition, SEM-EDS images show that HM with a high porosity and specific surface area coexists well with cement, which promotes the stabilization of lead. In conclusion, HM contributes to decreasing the mobility and bioavailability of lead and achieving environmental remediation.