Life cycle environmental impacts of regeneration options for anion exchange resin remediation of PFAS impacted water

Sonochemical degradation of PFAS in ion exchange regeneration wastes

One of the primary technologies currently being deployed for the removal of per- and polyfluoroalkyl substances (PFAS) from water is ion exchange (IX). For regenerable IX resins, concentrated PFAS in the resulting spent brine and/or still bottoms requires further treatment. This research demonstrated that PFAS in spent brine and still bottoms can be effectively degraded sonochemically at 1000 kHz. Overall, PFAS degradation was negatively impacted by high total organic carbon (TOC) and residual methanol (MeOH) solvent (up to 50 g/kg; 5% w:w), but was enhanced by the high chloride. The addition of caustic (up to 1 N NaOH) partially mitigated the inhibition by TOC and MeOH. Sonochemical degradation of individual PFAS compounds resulted in significant mineralization to form inorganic fluoride, but small quantities of volatile organic fluorine species (VOF) were noted. This is believed to be the first report of sonochemical degradation of PFAS in ion exchange regeneration wastes, and indicates the possibility for the application of this technology as part of a complete PFAS capture and destruction treatment train.

Can biotechnology lead the way toward a sustainable pharmaceutical industry?

The impact-intensive and rapidly growing pharmaceutical industry must ensure its sustainability. This study reveals that environmental sustainability assessments have been conducted for only around 0.2% of pharmaceuticals, environmental impacts have significant variations among the assessed products, and different impact categories have not been consistently studied. Highly varied impacts require assessing more products to understand the industry's sustainability status. Reporting all impact categories will be crucial, especially when comparing production technologies. Biological production of (semi)synthetic pharmaceuticals could reduce their environmental costs, though the high impacts of biologically produced monoclonal antibodies should also be optimized. Considering the sustainability potential of biopharmaceuticals from economic, environmental, and social perspectives, collaboratively guiding their immense market growth would lead to the industry's sustainability transition.

Enhanced denitrification performance of granular sludge for the treatment of waste brine from ion exchange resin process

Ion exchange resin process is a widely used process in wastewater treatment plants, but its waste brine is characterized by high salinity and nitrate concentration, leading to costly treatment. This study innovatively explored the use of an up-flow anaerobic sludge bed (USB) for the treatment of waste brine from ion exchange resin process, following a pilot-scale ion exchange resin process. Specifically, the D890 ion exchange resin was employed for nitrate removal from secondary effluent, with resin regeneration using 4% NaCl solution. The USB was inoculated with anaerobic granular sludge and acclimated under various single-factor conditions, which revealed the optimal pH range of 6.5-9, salt concentration of 2%, hydraulic retention time of 12 h, C/N ratio of 3.3, and up-flow velocity of 1.5 m/h for reactor operation. This study provides a novel approach for the cost-effective treatment of waste brine from ion exchange resin process. The study found that the denitrification efficiency was highest when the NO3--N concentration was around 200 mg/L, with NO3--N and TN removal rates exceeding 95% and 90%, respectively, under optimal operating conditions. Characterization of the granular sludge during different phases of the operation revealed a significant increase in proteobacteria and gradually became the dominant species over time. This study presents a novel, cost-effective approach to treat waste brine from ion exchange resin process, and the long-term stable operation of the reactor offers a reliable option for resin regeneration wastewater treatment.

Thermal Phase Transition and Rapid Degradation of Forever Chemicals (PFAS) in Spent Media Using Induction Heating

In this study, we have developed an innovative thermal degradation strategy for treating per- and polyfluoroalkyl substance (PFAS)-containing solid materials. Our strategy satisfies three criteria: the ability to achieve near-complete degradation of PFASs within a short timescale, nonselectivity, and low energy cost. In our method, a metallic reactor containing a PFAS-laden sample was subjected to electromagnetic induction that prompted a rapid temperature rise of the reactor via the Joule heating effect. We demonstrated that subjecting PFASs (0.001-12 μmol) to induction heating for a brief duration (e.g., <40 s) resulted in substantial degradation (>90%) of these compounds, including recalcitrant short-chain PFASs and perfluoroalkyl sulfonic acids. This finding prompted us to conduct a detailed study of the thermal phase transitions of PFASs using thermogravimetric analysis and differential scanning calorimetry (DSC). We identified at least two endothermic DSC peaks for anionic, cationic, and zwitterionic PFASs, signifying the melting and evaporation of the melted PFASs. Melting and evaporation points of many PFASs were reported for the first time. Our data suggest that the rate-limiting step in PFAS thermal degradation is linked with phase transitions (e.g., evaporation) occurring on different time scales. When PFASs are rapidly heated to temperatures similar to those produced during induction heating, the evaporation of melted PFAS slows down, allowing for the degradation of the melted PFAS.

Life cycle assessment and life cycle cost analysis of anion exchange and granular activated carbon systems for remediation of groundwater contaminated by per- and polyfluoroalkyl substances (PFASs)

Anion exchange resin (AER) and granular activated carbon (GAC) have emerged as prominent technologies for treatment of waters contaminated with per- and polyfluoroalkyl substances (PFASs). This study compares the life cycle environmental impacts and life cycle costs of remediating PFAS-contaminated groundwater with these competing technologies, using field pilot data to inform model inputs. Comparative analysis indicates that AER systems employing single-use "PFAS-selective" resins have lower environmental impacts and costs than systems using regenerable resins or GAC adsorbents, supporting its use in future remediation efforts. Use of GAC operated as a single-use adsorbent led to the highest emissions as well as the highest treatment costs, with thermally-reactivated GAC proving to be less impactful than regenerable AER treatment. Sensitivity analyses highlighted the dominance of media usage rate (MUR), which is highly dependent on the selected PFAS treatment goals, to determine environmental impacts and costs over a 30-year system life cycle. Selection of very stringent changeout criteria (e.g., detection of any PFASs in effluent) significantly reduces the advantages of single-use resins. For regenerable AER, environmental impacts were dominated by management of the PFAS-contaminated brine/co-solvent waste stream used to regenerate the adsorbent, as well as the cosolvent content of the regenerant mixture and the cosolvent recovery efficiency achieved via on-site distillation. High impacts estimated for GAC adsorption, the result of high MUR relative to ion exchange media, can be significantly reduced if spent adsorbents are reused after thermal reactivation, but impacts are still greater than those predicted for single-use ion exchange systems. Findings are expected to hold across a range of diverse sites, including drinking water systems treating more dilute sources of PFAS contamination, as PFAS breakthrough was not found to be highly sensitive to sourcewater PFAS concentrations.

Mechanistic Investigations of Thermal Decomposition of Perfluoroalkyl Ether Carboxylic Acids and Short-Chain Perfluoroalkyl Carboxylic Acids

In this study, we investigated the thermal decomposition mechanisms of perfluoroalkyl ether carboxylic acids (PFECAs) and short-chain perfluoroalkyl carboxylic acids (PFCAs) that have been manufactured as replacements for phased-out per- and polyfluoroalkyl substances (PFAS). C-C, C-F, C-O, O-H, and C═C bond dissociation energies were calculated at the M06-2X/Def2-TZVP level of theory. The α-C and carboxyl-C bond dissociation energy of PFECAs declines with increasing chain length and the attachment of an electron-withdrawing trifluoromethyl (-CF3) group to the α-C. Experimental and computational results show that the thermal transformation of hexafluoropropylene oxide dimer acid to trifluoroacetic acid (TFA) occurs due to the preferential cleavage of the C-O ether bond close to the carboxyl group. This pathway produces precursors of perfluoropropionic acid (PFPeA) and TFA and is supplemented by a minor pathway (CF3CF2CF2OCFCF3COOH → CF3CF2CF2· + ·OCFCF3COOH) through which perfluorobutanoic acid (PFBA) is formed. The weakest C-C bond in PFPeA and PFBA is the one connecting the α-C and the β-C. The results support (1) the C-C scission in the perfluorinated backbone as an effective PFCA thermal decomposition mechanism and (2) the thermal recombination of radicals through which intermediates are formed. Additionally, we detected a few novel thermal decomposition products of studied PFAS.

A review of the occurrence, transformation, and removal technologies for the remediation of per- and polyfluoroalkyl substances (PFAS) from landfill leachate

Per- and polyfluoroalkyl substances (PFAS) are persistent organic pollutants (POPs) that pose significant environmental and human health risks. The presence of PFAS in landfill leachate is becoming an increasingly concerning issue. This article presents a comprehensive review of current knowledge and research gaps in monitoring and removing PFAS from landfill leachate. The focus is on evaluating the effectiveness and sustainability of existing removal technologies, and identifying areas where further research is needed. To achieve this goal, the paper examines the existing technologies for monitoring and treating PFAS in landfill leachate. The review emphasizes the importance of sample preparation techniques and quality assurance/quality control measures in ensuring accurate and reliable results. Then, this paper reviewed the existing technologies for removal and remediation of PFAS in landfill leachates, such as adsorption, membrane filtration, photocatalytic oxidation, electrocatalysis, biodegradation, and constructed wetlands. Additionally, the paper summarizes the factors that exhibit the performance of various treatment technologies: reaction time, experimental conditions, and removal rates. Furthermore, the paper evaluates the potential application of different remediation technologies (i.e., adsorption, membrane filtration, photocatalytic oxidation, electrocatalysis, biodegradation, and constructed wetlands, etc.) in treating landfill leachate containing PFAS and its precursors, such as fluorotelomeres like FTOH and FTSs. The review highlights the importance of considering economic, technical, and environmental factors when selecting control measures. Overall, this article aims to provide guidance for promoting environmental protection and sustainable development in the context of PFAS contamination in landfill leachate.

Combination of adsorption/desorption and photocatalytic reduction processes for PFOA removal from water by using an aminated biosorbent and a UV/sulfite system

Per- and polyfluoroalkyl substances (PFAS) are stable organic chemicals, which have been used globally since the 1940s and have caused PFAS contamination around the world. This study explores perfluorooctanoic acid (PFOA) enrichment and destruction by a combined method of sorption/desorption and photocatalytic reduction. A novel biosorbent (PG-PB) was developed from raw pine bark by grafting amine groups and quaternary ammonium groups onto the surface of bark particles. The results of PFOA adsorption at low concentration suggest that PG-PB has excellent removal efficiency (94.8%-99.1%, PG-PB dosage: 0.4 g/L) to PFOA in the concentration range of 10 μg/L to 2 mg/L. The PG-PB exhibited high adsorption efficiency regarding PFOA, being 456.0 mg/g at pH 3.3 and 258.0 mg/g at pH 7 with an initial concentration of 200 mg/L. The groundwater treatment reduced the total concentration of 28 PFAS from 18 000 ng/L to 9900 ng/L with 0.8 g/L of PG-PB. Desorption experiments examined 18 types of desorption solutions, and the results showed that 0.05% NaOH and a mixture of 0.05% NaOH + 20% methanol were efficient for PFOA desorption from the spent PG-PB. More than 70% (>70 mg/L in 50 mL) and 85% (>85 mg/L in 50 mL) of PFOA were recovered from the first and second desorption processes, respectively. Since high pH promotes PFOA degradation, the desorption eluents with NaOH were directly treated with a UV/sulfite system without further adjustment. The final PFOA degradation and defluorination efficiency in the desorption eluents with 0.05% NaOH + 20% methanol reached 100% and 83.1% after 24 h reaction. This study proved that the combination of adsorption/desorption and a UV/sulfite system for PFAS removal is a feasible solution for environmental remediation.

Recent advances in the remediation of perfluoroalkylated and polyfluoroalkylated contaminated sites

Per- and polyfluoroalkyl substances (PFASs) are compounds used since 1940 in various formulations in the industrial and consumer sectors due to their high chemical and thermal stability. In recent years, PFASs have caused global concern due to their presence in different water and soil matrices, which threatens the environment and human health. These compounds have been reported to be linked to the development of serious human diseases, including but not limited to cancer. For this reason, PFASs have been considered as persistent organic compounds (COPs) and contaminants of emerging concern (CECs). Therefore, this work aims to present the advances in remediation of PFASs-contaminated soil and water by addressing the current literature. The performance and characteristics of each technique were addressed deeply in this work. The reviewed literature found that PFASs elimination studies in soil and water were carried out at a laboratory and pilot-scale in some cases. It was found that ball milling, chemical oxidation and thermal desorption are the most efficient techniques for the removal of PFASs in soils, however, phyto-microbial remediation is under study, which claims to be a promising technique. For the remediation of PFASs-contaminated water, the processes of electrocoagulation, membrane filtration, ozofractionation, catalysis, oxidation reactions - reduction, thermolysis and destructive treatments with plasma have presented the best results. It is noteworthy that hybrid treatments have also proved to be efficient techniques in the removal of these contaminants from soil and water matrices. Therefore, the improvisation and implication of existing techniques on a field-scale are greatly warranted to corroborate the yields obtained on a pilot- and laboratory-scale.

Recent trends in degradation strategies of PFOA/PFOS substitutes

The global elimination and restriction of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), respectively, have urged manufacturers to shift production to their substitutes which still pose threat to the environment with their bioaccumulation, toxicity and migration issues. In this context, efficient technologies and systematic mechanistic studies on the degradation of PFOA/PFOS substitutes are highly desirable. In this review, we summarize the progress in degrading PFOA/PFOS substitutes, including four kinds of mainstream methods. The pros and cons of the present technologies are analyzed, which renders the discussion of future prospects on rational optimizations. Additional discussion is made on the differences in the degradation of various kinds of substitutes, which is compared to the PFOA/PFOS and derives designing principles for more degradable F-containing compounds.

Removal of perfluoroalkyl acids and common drinking water contaminants by weak-base anion exchange resins: Impacts of solution pH and resin properties

The underlying chemistry of weak-base (WB) anion exchange resins (AERs) for contaminant removal from water is not well documented in the literature. To address this, batch adsorption experiments were conducted at pH 4, 7, and 10 using two representative WB-AERs (polyacrylic IRA67 and polystyrene IRA96) and two representative strong-base (SB) AERs (polyacrylic IRA458 and polystyrene A520E), of differing polymer composition, for the removal of nitrate, sulfate, 3-phenylpropionic acid (3-PPA) as surrogate for natural organic matter, and six perfluoroalkyl acids (PFAAs). Under acidic (pH 4) and neutral (pH 7) conditions, the selectivity of AERs for each contaminant was predominantly influenced by polymer composition followed by the size of the resin functional group. This result reflected the WB-AERs being fully protonated and functioning identical to SB-AERs. Isotherm model parameters revealed WB-AER had higher capacity than SB-AER with analogous polymer composition and porosity regardless of resin selectivity for each contaminant. Under basic conditions (≥ pH 10), contaminant removal by WB-AERs declined due to deprotonation of the tertiary amine functional groups. Removal of PFAAs by the more hydrophobic polystyrene WB-AER (IRA96) remained approximately constant with changing pH, which was possibly due to electrostatic interactions with remaining protonated amine functional groups on the resin.

Assessing the environmental impacts and costs of biochar and monitored natural attenuation for groundwater heavily contaminated with volatile organic compounds

Although biochar (BC) and monitored natural attenuation (MNA) are regarded as green technologies for remediating volatile organic compounds (VOCs) contaminated groundwater, their life cycle environmental impacts and costs have not been systematically quantified. This work assessed the primary and secondary environmental impacts and the cost of three options for remediating the groundwater at a closed pesticide manufacturing plant site, which was contaminated by high levels of multiple VOCs and is undergoing MNA. The studied options include a combination of MNA and BC (MNA + BC), BC, and pump and treat (PT). The environmental impacts were examined through a Life Cycle Assessment (LCA) using the ReCiPe 2016 method. The costs were evaluated using a Life Cycle Cost (LCC) method created in the SimaPro. The LCA results show that the overall environmental impacts follow the sequence of PT > BC > MNA + BC, but MNA + BC shows evident primary impacts. The CO₂ eq emissions generated from PT are more than five times of MNA + BC or BC. The cement, electricity, and steel for construction, and the operation energy are the environmental hotspots in PT. In MNA + BC and BC, the electricity for feedstock pyrolysis is the environmental hotspot, while the use of BC by-products to generate heat and power has positive environmental credit that compensates other negative environmental burdens. Incorporating institutional controls, using renewable energy and recycled or alternative materials, and developing BC with superior adsorption capacity are recommended to optimize the remediation strategies. The LCC results show that PT renders the highest cost, with cement and electricity being the two most expensive items. Electricity is the dominant contributor to the costs of MNA + BC and BC, while the avoided heat and power generation can save the cost of other items. Overall, this study provides scientific support to develop and optimize green remediation solutions for VOCs contaminated groundwater.

Bibliometric Analysis of Groundwater’s Life Cycle Assessment Research

Groundwater is an important water resource that accounts for 30% of the world’s freshwater. 97% of this extracted groundwater is for drinking and human use. Due to anthropogenic activities, this resource is affected and, consequently, its life cycle is modified, changing its natural state. This paper aims to analyse the scientific production that deals with the study of groundwater’s Life Cycle Assessment (LCA), using bibliometric methods. Thus, it contributes to the evolution of knowledge of this resource in terms of its use (environmental, economic and social). The methodological process includes: (i) selection and analysis of search topics in the Scopus and Web of Science (WoS) databases; (ii) application of Bibliometrix and Visualisation of Similarity Viewer (VOSviewer) software to the data collected; (iii) scientific structure of the relation of the topics groundwater and life cycle, considering programme lines and relations in their sub-themes; (iv) literature review of Author keywords. A total of 780 papers were selected, 306 being from Scopus, 158 from WoS and 316 published in both databases. The time evolution of the analysed data (publications) indicates that groundwater LCA studies have seen exponential growth (between 1983 and 2021). In addition, it has three development periods: introduction (years between 1983 and 2001), growth (between 2002 and 2011) and maturation (between 2012 and 2021). At the country level (origin of contributions authors), the USA dominates the total scientific production with 24.7%, followed by Denmark with 12.8% and 10.3% for China. Among the main topics of study associated with LCA are those focused on: the proposal of remediation methods, the application and development of technologies and the use of water resources by the urban community. This study allows establishing new trends in agricultural development issues about irrigation efficiency, wastewater reuse, mining and treatment, climate change in a circular economy scheme related to sustainability and life cycle assessment.