Showing papers by "Pedro J. J. Alvarez published in 2017"
TL;DR: A novel nitrogen-doped carbonaceous nanosphere catalyst is developed by carbonization of polypyrrole, which was prepared through a scalable chemical oxidative polymerization and exhibited the best catalytic performance for PMS activation.
Abstract: Metal-free carbonaceous materials, including nitrogen-doped graphene and carbon nanotubes, are emerging as alternative catalysts for peroxymonosulfate (PMS) activation to avoid drawbacks of conventional transition metal-containing catalysts, such as the leaching of toxic metal ions. However, these novel carbocatalysts face relatively high cost and complex syntheses, and their activation mechanisms have not been well-understood. Herein, we developed a novel nitrogen-doped carbonaceous nanosphere catalyst by carbonization of polypyrrole, which was prepared through a scalable chemical oxidative polymerization. The defective degree of carbon substrate and amount of nitrogen dopants (i.e., graphitic nitrogen) were modulated by the calcination temperature. The product carbonized at 800 °C (CPPy-F-8) exhibited the best catalytic performance for PMS activation, with 97% phenol degradation efficiency in 120 min. The catalytic system was efficient over a wide pH range (2–9), and the reaction of phenol degradation h...
466 citations
Virginia Tech1, Rice University2, University at Buffalo3, Swiss Federal Institute of Aquatic Science and Technology4, Hong Kong Polytechnic University5, Catholic University of Portugal6, Indian Institute of Technology Madras7, University of Michigan8, University of Hong Kong9, Chinese Academy of Sciences10
TL;DR: The need for coordinated national and international strategies to combat the spread of resistance is advised, highlighting three essential components: Monitoring, Risk Assessment, and Mitigation of antibiotic resistance.
Abstract: Antibiotic resistance is a pervasive global health threat. To combat the spread of resistance, it is necessary to consider all possible sources and understand the pathways and mechanisms by which resistance disseminates. Best management practices are urgently needed to provide barriers to the spread of resistance and maximize the lifespan of antibiotics as a precious resource. Herein we advise upon the need for coordinated national and international strategies, highlighting three essential components: (1) Monitoring, (2) Risk Assessment, and (3) Mitigation of antibiotic resistance. Central to all three components is What exactly to monitor, assess, and mitigate? We address this question within an environmental framework, drawing from fundamental microbial ecological processes driving the spread of resistance.
219 citations
TL;DR: The removal efficiency of the A-60 fiber was above 83% of the initial value after nine regeneration cycles, and the Redlich-Peterson adsorption isotherm model provided the best fit of the equilibrium data.
150 citations
TL;DR: Gold ion (Au3+) was used as a model heavy metal ion to quantitatively assess the role of EPS in biomineralization and discern the responsible functional groups, indicating a previously overlooked, universally significant contribution of EPS to the reduction, mineralization, and potential detoxification of metal species with high oxidation state.
Abstract: Biomineralization is a critical process controlling the biogeochemical cycling, fate, and potential environmental impacts of heavy metals. Despite the indispensability of extracellular polymeric substances (EPS) to microbial life and their ubiquity in soil and aquatic environments, the role played by EPS in the transformation and biomineralization of heavy metals is not well understood. Here, we used gold ion (Au3+) as a model heavy metal ion to quantitatively assess the role of EPS in biomineralization and discern the responsible functional groups. Integrated spectroscopic analyses showed that Au3+was readily reduced to zerovalent gold nanoparticles (AuNPs, 2–15 nm in size) in aqueous suspension of Escherichia coli or dissolved EPS extracted from microbes. The majority of AuNPs (95.2%) was formed outside Escherichia coli cells, and the removal of EPS attached to cells pronouncedly suppressed Au3+ reduction, reflecting the predominance of the extracellular matrix in Au3+ reduction. XPS, UV–vis, and FTIR a...
147 citations
TL;DR: A vision for enhancing efficiency and resiliency of urban water systems is presented and approaches and research needs for overcoming associated implementation challenges are discussed.
Abstract: Innovation in urban water systems is required to address the increasing demand for clean water due to population growth and aggravated water stress caused by water pollution, aging infrastructure, and climate change. Advances in materials science, modular water treatment technologies, and complex systems analyses, coupled with the drive to minimize the energy and environmental footprints of cities, provide new opportunities to ensure a resilient and safe water supply. We present a vision for enhancing efficiency and resiliency of urban water systems and discuss approaches and research needs for overcoming associated implementation challenges.
124 citations
TL;DR: The results indicate that anchoring phosphate - or anions that exert similar effects on the TiO2 surface - might be a feasible strategy to counteract the inhibitory effect of NOM during photocatalytic water treatment.
Abstract: A major challenge for photocatalytic water purification with TiO2 is the strong inhibitory effect of natural organic matter (NOM), which can scavenge photogenerated holes and radicals and occlude ROS generation sites upon adsorption. This study shows that phosphate counteracts the inhibitory effect of humic acids (HA) by decreasing HA adsorption and mitigating electron–hole recombination. As a measure of the inhibitory effect of HA, the ratios of first-order reaction rate constants between photocatalytic phenol degradation in the absence versus presence of HA were calculated. This ratio was very high, up to 5.72 at 30 mg/L HA and pH 4.8 without phosphate, but was decreased to 0.76 (5 mg/L HA, pH 8.4) with 2 mM phosphate. The latter ratio indicates a surprising favorable effect of HA on TiO2 photocatalysis. FTIR analyses suggest that this favorable effect is likely due to a change in the conformation of adsorbed HA, from a multiligand exchange arrangement to a complexation predominantly between COOH groups...
98 citations
TL;DR: In this article, the level and function of extracellular polymeric substances (EPS) during the granulation of aerobic sludge used to treat p -chloroaniline ( p -ClA) wastewater were investigated.
92 citations
TL;DR: The results infer that there is a vertical mass flux of DBC and possible fractionation from the dissolved organic matter pool in the fluvial and estuarine systems, which have been overlooked in efforts to determine global carbon budgets and associated climate change implications.
Abstract: The fluvial export of dissolved black carbon (DBC) is a major land-ocean flux in the global black carbon cycle, affecting the size of refractory carbon pool in the oceans. The aggregation behavior of DBC is a significant determinant of its transport and vertical mass flux. In this study, the aggregation kinetics and interaction energy of DBC leached from biochar were investigated. DBC was mainly stabilized by hydration force and underwent structural compacting in divalent cation solutions. Na+ and Mg2+ had limited impact on the colloidal stability of DBC due to the strong hydration of these cations. Ca2+ and Ba2+ readily destabilized DBC by forming inner-sphere complexes, reducing its hydrophilicity. Consistently, charge reversal of DBC was observed with high concentrations of Ca2+ and Ba2+. Simulated sunlight exposure led to photo-oxidation of DBC, increasing its colloidal stability. DBC behaved nonconservatively in laboratory mixing experiments using estuary water samples due to aggregation/sedimentatio...
85 citations
TL;DR: In this article, a microbial fuel cell (MFC) fed with produced water (Barnett Shale), which produced power (47mW/m2) and accomplished a COD removal efficiency of 68% (influent COD 10,520-±-1340-mg/L).
56 citations
TL;DR: In this paper, a dual-functional reducing and stabilizing agent was used to form gold nanoparticles (AuNPs) of controlled size based on temperature, achieving an average size of ∼11nm at room temperature and 7nm at 80°C.
Abstract: We demonstrate sodium rhodizonate as a novel dual-functional reducing and stabilizing agent to form gold nanoparticles (AuNPs) of controlled size based on temperature. At room temperature (ca. 23 °C), the method generates AuNPs with an average size of ∼11 nm, whereas at 80 °C, it forms AuNPs with an average size of ∼7 nm. The rhodizonate-stabilized AuNPs readily bind to cellulose fibers (CF) while maintaining a high catalytic activity. The catalytic activity of the CF-supported AuNPs nanocomposites is demonstrated by the reduction of 4-nitrophenol (4-NP) and organic dyes such as methyl orange (MO), methylene blue (MB) in water. A glass column-based continuous catalytic reduction and its recyclability is also demonstrated for practical applications.
53 citations
TL;DR: A novel group-6 propane monooxygenase gene cluster (prmABCD) is identified in Mycobacterium dioxanotrophicus PH-06, which is a bacterium with superior dioxane degradation kinetics compared with CB1190.
Abstract: 1,4-Dioxane (dioxane) is a groundwater contaminant of emerging concern for which bioremediation may be a promising strategy. Several bacterial strains can metabolize dioxane or degrade it cometabolically. However, the molecular basis of dioxane biodegradation is only partially understood, and the gene coding for dioxane/tetrahydrofuran (THF) monooxygenase in Pseudonocardia dioxanivorans CB1190 is the only well-characterized catabolic gene. Here, we identify a novel group-6 propane monooxygenase gene cluster (prmABCD) in Mycobacterium dioxanotrophicus PH-06, which is a bacterium with superior dioxane degradation kinetics compared with CB1190. Whole genome sequencing of PH-06 revealed the existence of a single soluble di-iron monooxygenase (SDIMO). RNA sequencing and reverse transcription quantitative PCR (RT-qPCR) subsequently confirmed that all four components of this gene cluster are upregulated when PH-06 is grown on dioxane compared with growth on acetate or glucose as negative controls. This first cha...
TL;DR: The conjugation approach could extend the application of phages for microbial control by enhancing their delivery to relatively inaccessible locations within biofilms.
Abstract: Biofilms may shelter pathogenic or other problematic microorganisms that are difficult to eradicate due to hindered penetration of antimicrobial chemicals. Here, we demonstrate the potential for efficient bacterial suppression using polyvalent (broad host-range) phages attached to magnetic colloidal nanoparticle clusters (CNCs) that facilitate biofilm penetration under a relatively small magnetic field (660 gauss). The polyvalent phage PEL1 (Podoviridae family) was immobilized onto Fe3O4-based magnetic CNCs that had been coated with chitosan (and thus functionalized with amino groups). This facilitated conjugation with phages via covalent bonding (i.e., amide linkages) and enabled phage loading, which reached (5.2 ± 0.7) × 103 centers of infection per 1 μg of chitosan-coated CNCs (CS-Fe3O4). The plaque formation capability of PEL1–CS-Fe3O4 on Pseudomonas aeruginosa PA01 and Escherichia coli C3000 lawns was significantly higher than that of phages conjugated with similar CNCs that had been functionalized with carboxyl groups (99.1% vs. 3.2% Petri dish area of infection). In newly established biofilms formed from these two species on a glass surface, PEL1–CS-Fe3O4 removed 88.7 ± 2.8% of the biofilm coverage area after 6 h of treatment. Overall, this conjugation approach could extend the application of phages for microbial control by enhancing their delivery to relatively inaccessible locations within biofilms.
TL;DR: It is shown that polyvalent phages can propagate in soil bacteria and significantly enhance suppression of co-occurring enteric species in environments harboring enteric pathogens and soil bacteria.
Abstract: Bacteriophages are widely recognized for their importance in microbial ecology and bacterial control. However, little is known about how phage polyvalence (i.e., broad host range) affects bacterial suppression and interspecies competition in environments harboring enteric pathogens and soil bacteria. Here we compare the efficacy of polyvalent phage PEf1 versus coliphage T4 in suppressing a model enteric bacterium (E. coli K-12) in mixtures with soil bacteria (Pseudomonas putida F1 and Bacillus subtilis 168). Although T4 was more effective than PEf1 in infecting E. coli K-12 in pure cultures, PEf1 was 20-fold more effective in suppressing E. coli under simulated multispecies biofilm conditions because polyvalence enhanced PEf1 propagation in P. putida. In contrast, soil bacteria do not propagate coliphages and hindered T4 diffusion through the biofilm. Similar tests were also conducted under planktonic conditions to discern how interspecies competition contributes to E. coli suppression without the confoun...
TL;DR: It is shown that polyvalent (broad-host-range) phages proliferate and thrive in activated sludge microcosms, especially when added along with their production hosts.
Abstract: Bacteriophage-based microbial control could help address a growing need to attenuate the proliferation of antibiotic-resistant bacteria (ARB) in wastewater treatment plants (WWTPs). However, the infectivity of commonly isolated narrow-host-range phages decreases quickly upon addition to activated sludge (i.e., plaque-forming units had a half-life of 0.63 h). Here, we show that polyvalent (broad-host-range) phages proliferate and thrive in activated sludge microcosms, especially when added along with their production hosts. Polyvalent phage cocktails (PER01 and PER02) were significantly more effective than narrow-host-range coliphage cocktails (MER01 and MER02) in suppressing a model ARB [β-lactam-resistant Escherichia coli NDM-1, initially present at 6.2 ± 0.1 log10 colony-forming units (CFU)/mL]. After 5 days, the NDM-1 concentration significantly decreased to 3.8 ± 0.2 log10 CFU/mL in the presence of the polyvalent phage cocktail, compared to 4.7 ± 0.3 log10 CFU/mL for the coliphage cocktail treatment. ...
TL;DR: It is underscores the importance to account for photochemical effects to inform risk assessments and regulations of cadmium pigments which are currently based on their low solubility.
Abstract: Cadmium pigments are widely used in the polymer and ceramic industry. Their potential environmental risk is under debate, being the major barrier for appropriate regulation. We show that 83.0 ± 0.2% of hazardous cadmium ion (Cd2+) was released from the commercial cadmium sulfoselenide pigment (i.e., cadmium red) in aqueous suspension within 24 h under simulated sunlit conditions. This photodissolution process also generated sub-20 nm pigment nanoparticles. Cd2+ release is attributed to the reactions between photogenerated holes and the pigment lattices. The photodissolution process can be activated by both ultraviolet and visible light in the solar spectrum. Irradiation under alkaline conditions or in the presence of phosphate and carbonate species resulted in reduced charge carrier energy or the formation of insoluble and photostable cadmium precipitates on pigment surfaces, mitigating photodissolution. Tannic acid inhibited the photodissolution process by light screening and scavenging photogenerated ho...
TL;DR: Results illustrate the importance of considering the possibility of unintentional hindrance of catabolism associated with the addition of auxiliary carbon sources to bioremediate aquifers impacted with trace concentrations of dioxane.
TL;DR: Graphene oxide (GO) induced significant inhibitory effects on the growth of different unicellular organisms, including eukaryotes and prokaryotes, which highlights a potential indirect detrimental effect of nanomaterials (i.e. scavenging of critical nutrients), and encourages research on potential biomedical applications of GO-based materials to sequester iron and enhance treatment of iron-dependent diseases such as cancer and some pathogenic infections.
Abstract: Graphene oxide (GO)-based materials are increasingly being used in medical materials and consumer products. However, their sublethal effects on biological systems are poorly understood. Here, we re...
TL;DR: In this paper, the authors demonstrate that pretreatment of impacted soils with UVC-activated TiO2 in soil slurries could enhance bioremediation of heavy hydrocarbons in soils impacted by crude oil spills.
Abstract: Heavy hydrocarbons (HHCs) in soils impacted by crude oil spills are generally recalcitrant to biodegradation due to their low bioavailability and complex chemical structure. In this study, soils were pretreated with varying concentrations of ultraviolet radiation A (UVA) or ultraviolet radiation C (UVC) activated titanium dioxide (TiO2) (1%–5%) under varying moisture conditions (0%–300% water holding capacity (WHC)) to enhance biodegradation of HCCs and shorten remediation timeframes. We demonstrate that pretreatment of impacted soils with UVC-activated TiO2 in soil slurries could enhance bioremediation of HHCs. Total petroleum hydrocarbon (TPH) removal after 24 h exposure to UVC (254 nm and 4.8 mW/cm2) was (19.1 ± 1.6)% in slurries with 300% WHC and 5 wt-% TiO2. TPH removal was non-selective in the C15-C36 range and increased with moisture content and TiO2 concentration. In a 10-d bioremediation test, TPH removal in treated soil increased to (26.0 ± 0.9)%, compared to (15.4 ± 0.8)% for controls without photocatalytic pre-treatment. Enhanced biodegradation was also confirmed by respirometry. This suggests that addition of UVC-activated TiO2 to soil slurries can transform recalcitrant hydrocarbons into more bioavailable and biodegradable byproducts and increase the rate of subsequent biodegradation. However, similar results were not observed for soils pretreated with UVA activated TiO2. This suggests that activation of TiO2 by sunlight and direct addition of TiO2 to unsaturated soils within landfarming setting may not be a feasible approach. Nevertheless, less than 1% of UVA (7.5 mW/cm2) or UVC (1.4 mW/cm2) penetrated beyond 0.3 cm soil depth, indicating that limited light penetration through soil would hinder the ability of TiO2 to enhance soil bioremediation under land farming conditions.
TL;DR: The complete genome sequence of Mycobacterium dioxanotrophicus PH-06 is reported, which is capable of using 1,4-dioxane as a sole source of carbon and energy.
Abstract: We report here the complete genome sequence of Mycobacterium dioxanotrophicus PH-06, which is capable of using 1,4-dioxane as a sole source of carbon and energy. The reported sequence will enable the elucidation of this novel metabolic pathway and the development of molecular biomarkers to assess bioremediation potential at contaminated sites.
TL;DR: It is shown that HPβCD addition mitigates these adverse effects in human fibroblasts by significantly reducing LDLr and SREBP1 gene expression.
Abstract: Oxidative stress causes significant increases in both cholesterol uptake and intracellular accumulation of the aging biomarker lipofuscin Here we show that HPβCD addition mitigates these adverse effects in human fibroblasts by significantly reducing LDLr and SREBP1 gene expression In the absence of oxidative stress, HPβCD addition induces a paradoxical response, increasing cholesterol accumulation (but not lipofuscin) via upregulation of cholesterol biosynthesis These two distinct, but opposite effects highlight a previously overlooked therapeutic consideration: the cholesterol content of the treated cell determines which cholesterol pathways, either beneficial or harmful, are responsive to HPβCD