Per- and poly-fluoroalkyl substances in agricultural contexts and mitigation of their impacts using biochar: A review.

Growing concern over the presence of per- and polyfluoroalkyl substances (PFAS) in agricultural compartments (e.g., soil, water, plants, soil fauna) has led to an increased interest in scalable and economically feasible remediation technologies. Biochar is the product of pyrolyzing organic materials (crop waste, wood waste, manures, grasses) and has been used as a low-cost adsorbent to remove contaminants including PFAS. This review frames biochar as a strategy for mitigating the detrimental impacts of PFAS in agricultural systems and discusses the benefits of this strategy within the framework of the needs and challenges of contaminant remediation in agriculture. To gauge the optimal physicochemical characteristics of biochar in terms of PFAS adsorption, principal component analysis using >100 data points from the available literature was performed. The main biochar-based PFAS treatment strategies (water filtration, soil application, mixing with biosolids) were also reviewed to highlight the benefits and complications of each. Life cycle analyses on the use of biochar for contaminant removal were summarized, and data from selected studies were used to calculate (for the first time) the global warming potential and net energy demand of various agriculturally important biochar classes (crop wastes, wood wastes, manures) in relation to their PFAS adsorption performance. This review serves to identify key gaps in our knowledge of (i) PFAS adsorption by biochars in agricultural remediation applications and (ii) environmental costs/benefits of biochars in relation to their adsorptive properties toward PFAS. The concepts introduced in this review may assist in developing large-scale biochar-based PFAS remediation strategies to help protect the agricultural food production environment.

Carbon/nitrogen ratios determine biofilm formation and characteristics in model microbial cultures.

The influence of growth medium water chemistry, specifically carbon/nitrogen (C/N) molar ratios, on the characteristics and development of biofilms of the model microorganism Pseudomonas aeruginosa was investigated. C/N = 9 had a unique effect on biofilm composition as well as quorum sensing (QS) pathways, with higher concentrations of carbohydrates and proteins in the biofilm and a significant upregulation of the QS gene lasI in planktonic cells. The effect of C/N ratio on total attached biomass was negligible. Principal component analysis revealed a different behavior of most outputs such as carbohydrates and QS chemicals at C/N = 9, and pointed to correlations between parameters of biofilm formation and steady state distribution of cells and extracellular components. C/N ratio was also shown to influence organic compound utilization by both planktonic and sessile organisms, with a maximum chemical oxygen demand (COD) removal of 83% achieved by biofilms at C/N = 21. Planktonic cells achieved higher COD removal rates, but greater overall rates after six days occurred in biofilms. The development of a dual-species biofilm of P. aeruginosa and Nitrobacter winogradskyi was also influenced by C/N, with increase in the relative abundance of the slower-growing N. winogradskyi above C/N = 9. These results indicate that altering operational parameters related to C/N would be relevant for mitigating or promoting biofilm formation and function depending on the desired industrial application or treatment configuration.

Zeolite performance in removal of multicomponent heavy metal contamination from wastewater.

Efficient removal of heavy metal pollutants from wastewater by ion-exchange sorbents requires knowledge and understanding of the interplay between the adsorption patterns of the different components. The present study elucidates the simultaneous adsorption characteristics of six toxic heavy metal cations (Cd2+, Cr3+, Cu2+, Ni2+, Pb2+, and Zn2+) by two synthetic (13X and 4 A) and one natural (clinoptilolite) zeolite from solutions containing equimolar mixtures of the six metals. Equilibrium adsorption isotherms and equilibration dynamics were obtained by ICP-OES and complemented by EDXRF. An order of magnitude lower adsorption efficiency was exhibited by clinoptilolite (maximum of 0.12 mmol ions/g zeolite), relative to that obtained by the synthetic zeolites 13X and 4 A (a maximum of 2.9 and 1.65 mmol ions/g zeolite respectively). The strongest affinities to both zeolites were demonstrated by Pb2+ and Cr3+ (1.5 and 0.85 mmol/g zeolite respectively for 13X, and 0.8 and 0.4 mmol/g zeolite respectively for 4 A adsorbed from the highest solution concentration). The weakest affinities were observed by Cd2+ (0.1 mmol/g for both zeolites), Ni2+ (0.2 and 0.1 mmol/g for 13X and 4 A respectively), and Zn2+ (0.1 mmol/g for both zeolites). Large differences were observed between the two synthetic zeolites in terms of their equilibration dynamics and adsorption isotherms. Pronounced maxima were displayed in the adsorption isotherms for zeolites 13X and 4 A. The decline in adsorption of the weaker adsorbing ions with the increase in total solution concentration was attributed to the thermodynamic equilibrium between the ions adsorbed on the zeolite surface and those in the solution. Regeneration by 3 M KCL eluting solution resulted in considerable reduction in adsorption capacities following each desorption cycle.

Enhanced removal of per- and polyfluoroalkyl substances in complex matrices by polyDADMAC-coated regenerable granular activated carbon.

Granular activated carbon (GAC) has been used to remove per- and polyfluoroalkyl substances (PFASs) from industrial or AFFF-impacted waters, but its effectiveness can be low because adsorption of short-chained PFASs is ineffective and its sites are exhausted rapidly by co-contaminants. To increase adsorption of anionic PFASs on GAC by electrostatic attractions, we modified GAC's surface with the cationic polymer poly diallyldimethylammonium chloride (polyDADMAC) and tested its capacity in complex water matrices containing dissolved salts and humic acid. Amending with concentrations of polyDADMAC as low as 0.00025% enhanced GAC's adsorption capacity for PFASs, even in the presence of competing ions. This suggests that electrostatic interactions with polyDADMAC's quaternary ammonium functional groups helped bind organic and inorganic ions as well as the headgroup of short-chain PFASs, allowing more overall PFAS removal by GAC. Evaluating the effect of polymer dose is important because excessive addition can block pores and reduce overall PFAS removal rather than increase it. To decrease the waste associated with this adsorption strategy by making the adsorbent viable for more than one saturation cycle, a regeneration method is proposed which uses low-power ultrasound to enhance the desorption of PFASs from the polyDADMAC-GAC with minimum disruption to the adsorbent's structure. Re-modification with the polymer after sonication resulted in a negligible decrease in the sorbent's capacity over four saturation rounds. These results support consideration of polyDADMAC-modified GAC as an effective regenerable adsorbent for ex-situ concentration step of both short and long-chain PFASs from real waters with high concentrations of competing ions and low PFAS loads.

A Readily Scalable, Clinically Demonstrated, Antibiofouling Zwitterionic Surface Treatment for Implantable Medical Devices.

Unlike growth on tissue, microbes can grow freely on implantable devices with minimal immune system intervention and often form resilient biofilms that continuously pump out pathogenic cells. The efficacy of antibiotics used to treat infection is declining due to increased rates of pathogenic resistance. A simple, one-step zwitterionic surface modification is developed to significantly reduce protein and microbial adhesion to synthetic materials and demonstrate the successful modification of several clinically relevant materials, including recalcitrant materials such as elastomeric polydimethylsiloxane. The treated surfaces exhibit robust adhesion resistance against proteins and microorganisms in both static and flow conditions. Furthermore, the surface treatment prevents the adhesion of mammalian fibroblast cells while displaying no cytotoxicity. To demonstrate the clinical efficacy of the novel technology in the real-world, a surface-treated, commercial silicone foley catheter is developed that is cleared for use by the U.S. Food and Drug Administration (K192034). 16 long-term catheterized patients received surface-treated catheters and completed a Patient Global Impression of Improvement (PGI-I) questionnaire. 10 out of 16 patients described their urinary tract condition post implantation as "much better" or "very much better" and 72% (n = 13) of patients desire to continue using the surface-treated catheter over conventional latex or silicone catheters.