Sewage sludge pyrolysis 'kills two birds with one stone': Biochar synergies with persulfate for pollutants removal and energy recovery.

The disposal and resource utilization of sewage sludge (SS) have always been significant challenges for environmental protection. This study employed straightforward pyrolysis to prepare iron-containing sludge biochar (SBC) used as a catalyst and to recover bio-oil used as fuel energy. The results indicated that SBC-700 could effectively activate persulfate (PS) to remove 97.2% of 2,4-dichlorophenol (2,4-DCP) within 60 min. Benefiting from the appropriate iron content, oxygen-containing functional groups and defective structures provide abundant active sites. Meanwhile, SBC-700 exhibits good stability and reusability in cyclic tests and can be easily recovered by magnetic separation. The role of non-radicals is emphasized in the SBC-700/PS system, and in particular, single linear oxygen (1O2) is proposed to be the dominant reactive oxygen. The bio-oil, a byproduct of pyrolysis, exhibits a higher heating value (HHV) of about 30 MJ/kg, with H/C and O/C ratios comparable to those of biodiesel. The energy recovery rate of the SS pyrolysis system was calculated at 80.5% with a lower input cost. In conclusion, this investigation offers a low-energy consumption and sustainable strategy for the resource utilization of SS while simultaneously degrading contaminants.

Effect of pyrite on the treatment of chlorophenolic compounds with zero-valent iron-Fenton process under uncontrolled pH conditions: reaction mechanism and biodegradability.

This current study explored the effect of pyrite on the treatment of chlorophenolic compounds (CP) by Fenton process with micron-sized zero-valent iron (ZVI) as the catalyst. The experiments were conducted in batch reactors with 100 mg L-1 CP, 0-0.02 M H2O2, and variable pyrite and ZVI doses (0-1 g L-1). Our findings show that while the reactor with 1 g L-1 ZVI as the only catalyst achieved only 10% CP removal efficiency due to rapid ZVI surface passivation and ZVI particle aggregation, the CP removal efficiency increased with increasing pyrite dose and reached 100% within couple of minutes in reactors with 0.8 g L-1 pyrite and 0.2 g L-1 ZVI. The CP removal was mainly driven by the oxidative treatment of CPs with some strong radicals such as hydroxyl radicals (•OH) while the adsorption onto the catalyst surface was only responsible for 10 to 25% of CP removals, depending on the type of CP studied. The positive impact of pyrite on CP removal by the ZVI/H2O2 system could be attributed to the ability of pyrite to (1) create an acidic environment for optimum Fenton process, (2) provide support material for ZVI to minimize ZVI particle agglomeration, and (3) stimulate iron redox cycling for improved surface site generation. Following oxidative Fenton treatment, the degradation intermediate products of CPs, including some aromatic compounds (benzoquinone, hydroquinone, etc.) and organic acids (e.g., acetic acid), became more biodegradable in comparison to their mother compounds. Overall, the treatment systems with a mixture of ZVI and pyrite as catalyst materials could offer a suitable cost-effective technology for the treatment of wastewater containing biologically non- or low-degradable toxic compounds such as chlorophenols.

Weak static magnetic fields facilitated highly efficient 2,4,6-trichlorophenol removal by sulfurized nanoscale zero-valent iron supported on biochar (BC-SNZVI) at neutral pH.

Sulfurized nanoscale zero-valent iron supported on biochar (BC-SNZVI) has been successfully synthesized for 2,4,6-trichlorophenol (2,4,6-TCP) removal, while was only effectively under acidic conditions. To obtain highly efficient removal of 2,4,6-TCP within a broader pH range, weak static magnetic fields (WMF) was applied in BC-SNZVI/2,4,6-TCP aqueous systems. Results showed 30 mT WMF supported the most extensive 2,4,6-TCP removal, and 87.4% of 2,4,6-TCP (initial concentration of 30 mg/L) was removed by 0.5 g/L BC-SNZVI at neutral pH (pH = 6.8) within 180 min, which was increased by 54.4% compared to that without WMF. The observed rate constant (Kobs) under 30 mT WMF was 2.1-fold greater than that without WMF. Although three typical anions (NO3- (0.5-10.0 mM), H2PO4- (0.05-0.5 mM), and HCO3- (0.5-5.0 mM)) still inhibited 2,4,6-TCP removal, WMF could efficiently alleviate the inhibitory effects. Moreover, 73.1% of 2,4,6-TCP was successfully removed by BC-SNZVI under WMF in natural water. WMF remarkably boosted the dechlorination of 2,4,6-TCP, increasing the 2,4,6-TCP dechlorination efficiency from 45.2% (in the absence of WMF) to 83.8% (in the presence of WMF) by the end of 300 min. And the complete dechlorination product phenol appeared within 10 min. Force analysis confirmed the magnetic field gradient force (FB) moved paramagnetic Fe2+ at the SNZVI surface along the direction perpendicular to the external applied field, promoting the mass-transfer controlled SNZVI corrosion. Corrosion resistance analysis revealed WMF promoted the electron-transfer controlled SNZVI corrosion by decreasing its self-corrosion potential (Ecorr). With the introduction of sulfur, the magnitude of FB doubled and the Ecorr decreased comparing with NZVI. Our findings provide a facile and viable strategy for treating chlorinated phenols at neutral pH.

Improvement strategy of citrate and biochar assisted nano-palladium/iron composite for effective dechlorination of 2,4-dichlorophenol.

Rapid passivation and aggregation of nanoscale zero-valent iron (nZVI) seriously limit its performance in the remediation of different contaminants from wastewater. To overcome such issues, in the present study, nano-palladium/iron (nPd/Fe) was simultaneously improved by biochar (BC) prepared from discarded peanut shells and green complexing agent sodium citrate (SC). For this purpose, a composite (SC-nPd/Fe@BC) was successfully synthesized to remove 2,4-dichlorophenol (2,4-DCP) from wastewater. In the SC-nPd/Fe@BC, BC acts as a carrier with dispersed nPd/Fe particles to effectively prevent its agglomeration, and increased the specific surface area of the composite, thereby improving the reactivity and stability of nPd/Fe. Characterization results demonstrated that the SC-nPd/Fe@BC composites were well dispersed, and the agglomeration was weakened. The formation of the passivation layer on the surface of the particles was inhibited, and the mechanism of SC and BC improving the reactivity of nPd/Fe was clarified. Different factors were found to influence the reductive dichlorination of 2,4-DCP, including Pd loading, Fe:C, SC addition, temperature, initial pH, and initial pollutant concentration. The dechlorination results revealed that the synergistic effect of the BC and SC made the removal efficiency and dechlorination rate of 2,4-DCP by SC-nPd/Fe@BC reached to 96.0 and 95.6%, respectively, which was better than that of nPd/Fe (removal: 46.2%, dechlorination: 45.3%). Kinetic studies explained that the dechlorination reaction of 2,4-DCP and the data were better represented by the pseudo-first-order kinetic model. The reaction rate constants followed the order of SC-nPd/Fe@BC (0.0264 min-1) > nPd/Fe@BC (0.0089 min-1) > SC-nPd/Fe (0.0081 min-1) > nPd/Fe (0.0043 min-1). Thus, SC-nPd/Fe@BC was capable of efficiently reducing 2,4-DCP and the dechlorination efficiency of BC and SC synergistically assisted composite on 2,4-DCP was much better than that of SC-nPd/Fe, nPd/Fe@BC and nPd/Fe. Findings suggested that SC-nPd/Fe@BC can be promising for efficient treatment of chlorinated pollutants.

Adaptive laboratory evolution of Rhodococcus rhodochrous DSM6263 for chlorophenol degradation under hypersaline condition.

BACKGROUND: Normally, a salt amount greater than 3.5% (w/v) is defined as hypersaline. Large amounts of hypersaline wastewater containing organic pollutants need to be treated before it can be discharged into the environment. The most critical aspect of the biological treatment of saline wastewater is the inhibitory/toxic effect exerted on bacterial metabolism by high salt concentrations. Although efforts have been dedicated to improving the performance through the use of salt-tolerant or halophilic bacteria, the diversities of the strains and the range of substrate spectrum remain limited, especially in chlorophenol wastewater treatment. RESULTS: In this study, a salt-tolerant chlorophenol-degrading strain was generated from Rhodococcus rhodochrous DSM6263, an original aniline degrader, by adaptive laboratory evolution. The evolved strain R. rhodochrous CP-8 could tolerant 8% NaCl with 4-chlorophenol degradation capacity. The synonymous mutation in phosphodiesterase of strain CP-8 may retard the hydrolysis of cyclic adenosine monophosphate (cAMP), which is a key factor reported in the osmoregulation. The experimentally verified up-regulation of intracellular cAMP level in the evolved strain CP-8 contributes to the improvement of growth phenotype under high osmotic condition. Additionally, a point mutant of the catechol 1,2-dioxygenase, CatAN211S, was revealed to show the 1.9-fold increment on activity, which the mechanism was well explained by molecular docking analysis. CONCLUSIONS: This study developed one chlorophenol-degrading strain with extraordinary capacity of salt tolerance, which showed great application potential in hypersaline chlorophenol wastewater treatment. The synonymous mutation in phosphodiesterase resulted in the change of intracellular cAMP concentration and then increase the osmotic tolerance in the evolved strain. The catechol 1,2-dioxygenase mutant with improved activity also facilitated chlorophenol removal since it is the key enzyme in the degradation pathway.

Synthesis of crown ether-based microporous organic networks: A new type of efficient adsorbents for chlorophenols.

Microporous organic networks (MONs) are a booming class of functional materials in elimination of environmental pollutants. However, the limit varieties of MONs still restrict their broad applications. Here we report the synthesis of a novel type of crown ether (CE)-based MONs via the coupling between brominated 18-crown-6 ether and different aromatic alkynyls. The constructed CE-based MONs integrates the good conjugation property of MONs and the inherent host-guest binding sites of CE, allowing the ultrafast and efficient adsorption and removal of a typical environmental priority pollutant 2,4,6-trichlorophenol (2,4,6-TCP). The hydrophobic CE-based MONs can also address the recovery challenge of unstable discrete CE in most organic and inorganic solvents. All CE-based MONs displayed fast adsorption kinetics (< 3 min) and large adsorption capacities (229.1-341.7 mg g-1) for 2,4,6-TCP. The CE-based MONs also gave stable adsorption capacities for 2,4,6-TCP in pH range of 4.0-6.0, NaCl concentration of 0-40 mg L-1, HA concentration of 0-30 mg L-1, or H2O2 ratio of < 5 %. Density functional theory calculation, Fourier transform infrared and X-ray photoelectron spectra evaluation revealed adsorption process involved hydrophobic, π-π and hydrogen bonding interactions. The CE-based MONs also showed favorable reusability and good adsorption for other toxic chlorophenols. This work highlights the potential of CE-based MONs in contaminants elimination.

Chlorination of para-substituted phenols: Formation of α, ß-unsaturated C4-dialdehydes and C4-dicarboxylic acids.

Despite the widespread occurrence of phenols in anthropogenic and natural compounds, their fate in reactions with hypochlorous acid (HOCl), one of the most common water treatment disinfectants, remains incompletely understood. To close this knowledge gap, this study investigated the formation of disinfection by-products (DBPs) in the reaction of free chlorine with seven para-substituted phenols. Based on the chemical structures of the DBPs and the reaction mechanisms leading to their formation, the DBPs were categorized into four groups: chlorophenols, coupling products, substituent reaction products, and ring cleavage products. In contrast to previous studies that investigated the formation of early-stage chlorophenols, the primary focus of this study was on the elucidation of novel ring cleavage products, in particular α, ß-unsaturated C4-dialdehydes, and C4-dicarboxylic acids, which, for the first time, were identified and quantified in this study. The molar yields of 2-butene-1,4-dial (BDA), one of the identified α, ß-unsaturated C4-dialdehydes, varied among the different phenolic compounds, reaching a maximum value of 10.4% for bisphenol S. Molar yields of 2-chloromaleic acid (Cl-MA), one of the identified C4-dicarboxylic acids, reached a maximum value of 30.5% for 4-hydroxy-phenylacetic acid under given conditions. 2,4,6-trichlorophenol (TCP) was shown to be an important intermediate of the parent phenols and the C4-ring cleavage products. Based on the temporal trends of α, ß-unsaturated C4-dialdehydes and C4-dicarboxylic acids, their formation is likely attributable to two separate ring cleavage pathways. Based on the obtained results, an overall transformation pathway for the reaction of para-substituted phenols with free chlorine leading to the formation of novel C4 ring cleavage products was proposed.

The Pharmacology and Clinical Efficacy of Antiseizure Medications: From Bromide Salts to Cenobamate and Beyond.

Epilepsy is one of the most common and disabling chronic neurological disorders. Antiseizure medications (ASMs), previously referred to as anticonvulsant or antiepileptic drugs, are the mainstay of symptomatic epilepsy treatment. Epilepsy is a multifaceted complex disease and so is its treatment. Currently, about 30 ASMs are available for epilepsy therapy. Furthermore, several ASMs are approved therapies in nonepileptic conditions, including neuropathic pain, migraine, bipolar disorder, and generalized anxiety disorder. Because of this wide spectrum of therapeutic activity, ASMs are among the most often prescribed centrally active agents. Most ASMs act by modulation of voltage-gated ion channels; by enhancement of gamma aminobutyric acid-mediated inhibition; through interactions with elements of the synaptic release machinery; by blockade of ionotropic glutamate receptors; or by combinations of these mechanisms. Because of differences in their mechanisms of action, most ASMs do not suppress all types of seizures, so appropriate treatment choices are important. The goal of epilepsy therapy is the complete elimination of seizures; however, this is not achievable in about one-third of patients. Both in vivo and in vitro models of seizures and epilepsy are used to discover ASMs that are more effective in patients with continued drug-resistant seizures. Furthermore, therapies that are specific to epilepsy etiology are being developed. Currently, ~ 30 new compounds with diverse antiseizure mechanisms are in the preclinical or clinical drug development pipeline. Moreover, therapies with potential antiepileptogenic or disease-modifying effects are in preclinical and clinical development. Overall, the world of epilepsy therapy development is changing and evolving in many exciting and important ways. However, while new epilepsy therapies are developed, knowledge of the pharmacokinetics, antiseizure efficacy and spectrum, and adverse effect profiles of currently used ASMs is an essential component of treating epilepsy successfully and maintaining a high quality of life for every patient, particularly those receiving polypharmacy for drug-resistant seizures.

Preparation of carbon dots-hematite quantum dots-loaded hydroxypropyl cellulose-chitosan nanocomposites for drug delivery, sunlight catalytic and antimicrobial application.

In this project, we studied the thermal and chemical method for the synthesis of carbon dots (CDs)/Hematite (α-Fe2O3) quantum dots and the preparation of hydroxypropyl cellulose cross-linked chitosan (HPCCS) and ulvan (UN) was performed by chemical method. Carbon dots/α-Fe2O3 quantum dots with size distribution of 3-5 nm were completely encapsulated in the HPCCS/UN NPs to obtain composites, which indicated unique characteristics with respect to antimicrobial, pH-responsive and optical properties. The CDs-HQDs/HPCCS/UN nanocomposites exhibited a single-excitation (440 nm), dual-emission fluorescence property (505 nm and 628 nm for green and red light from CDs-HQDs and HPCCS/UN NPs). The nanocomposites played as a pH-responsive drug delivery process to release ulvan at a fast rate in pH 7.4 buffer solution but at a slow rate in low pH solutions. The CDs-HQDs/HPCCS/UN nanocomposites gained the highest photocatalytic activity for degrading 4-chlorophenol (4-CPh) as a pollutant (>98% during 70 min under sunlight irradiation). Moreover, the nanocomposites indicated great inhibitory influences towards bacterial and fungal.

Glutathione Conjugation and Protein Adduction by Environmental Pollutant 2,4-Dichlorophenol In Vitro and In Vivo.

2,4-Dichlorophenol (2,4-DCP), an environmental pollutant, was reported to cause hepatotoxicity. The biochemical mechanisms of 2,4-DCP induced liver injury remain unknown. The present study showed that 2,4-DCP is chemically reactive and spontaneously reacts with GSH and bovine serum albumin to form GSH conjugates and BSA adducts. The observed conjugation/adduction apparently involved the addition of GSH and departure of chloride via the ipso substitution pathway. Two biliary GSH conjugates and one urinary N-acetyl cysteine conjugate were observed in rats given 2,4-DCP. The N-acetyl cysteine conjugate was chemically synthesized and characterized by mass spectrometry and NMR. As expected, 2,4-DCP was found to modify hepatic protein at cysteine residues in vivo by the same chemistry. The observed protein adduction reached its peak at 15 min and revealed dose dependency. The new findings allowed us to better understand the mechanisms of the toxic action of 2,4-DCP.

Fabrication of a novel nontoxic trichlorophenol-epichlorohydrin-based compound with high antimicrobial activity and thermal stability.

The aim of this study was to modify a discontinued, toxic antiseptic agent 2,4,5-trichlorophenol (TCP) by reacting it with epichlorohydrin (ECH) to obtain a nontoxic novel compound with similar antimicrobial effectiveness. A novel compound named {[1,3-bis(2,4,5-trichlorophenoxy) propan-2-yl] oxy}-3-(2,4,5-trichlorophenoxy) hexan-2-ol (TPTH) was synthesized from this reaction. Chemical and physical structures of the product were characterized by FTIR, MS, Uv-vis, NMR, SEM and TEM. The thermal stability of TPTH was evaluated by conducting thermogravimetric analysis. Biological interactions of the compound were investigated by performing antimicrobial activity and cytotoxicity assays. The compound displayed a good antimicrobial activity where minimum inhibitor concentrations were found to be 0.02, 0.08, and 0.15 µg mL-1 against Staphylococcus aureus (S. aureus), Methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli (E. coli) respectively. Additionally, well diffusion assay demonstrated that, the zone of inhibitions for S. aureus, MRSA and E. coli were 24 mm, 22 mm and 18 mm, respectively. Cytotoxicity assay results revealed that TPTH is nontoxic against cells at effective anti-microbial concentrations. TPTH shows thermal stability up to 220 °C. Results here demonstrate the successful conversion of toxic TCP to a nontoxic form; TPTH with a good anti-microbial activity and thermal stability.

Effects of different carbon sources on 2,4,6-trichlorophenol degradation in the activated sludge process.

The effects of different carbon sources on the enrichment of 2,4,6TCP-degrading microbes and on reactor stability were was investigated using a lab-scale sequencing batch reactor (SBR). Glucose, sucrose, and starch were selected as different carbon sources because of the different molecular weights. The sucrose-fed activated sludge (AS) exhibited faster adaption and higher degradation rates for 2,4,6-TCP in long-term operation and typical cycles compared to that fed with glucose and starch. Large amounts of extracellular polymeric substance (EPS; 117.54 mg/gVSS) were induced from AS after adding starch, leading to a high SVI (191 mL/g) and poor sludge settling. This suggests that macromolecular carbon sources might have a detrimental effect on the reactor operation. Moreover, the high removal efficiency for TOC and chloride ions was achieved in a typical cycle of all SBRs, indicating that AS could completely mineralize 2,4,6-TCP. On average, more than 90% of the COD could be removed in all SBRs during long-term operation. Glucose, sucrose, and starch facilitated the development of a different microbial community compared to the seeding sludge, making Chloroflexi, Actinobacteria, and Proteobacteria the dominant phylum in the corresponding SBR. The microbial abundance associated with the metabolism of 2,4,6-TCP reached 81.02% due to the addition of sucrose. The results of this study could provide a potential guide for the effective selection of carbon sources in the treatment of chlorophenol wastewater.

Immobilized polyphenol oxidase: Preparation, optimization and oxidation of phenolic compounds.

Polyphenol oxidase (PPO) was immobilized on chitosan/montmorillonite (CTS/MMT) and chitosan-gold nanoparticles/montmorillonite (CTS-AuNPs/MMT) composites, respectively. Taguchi method was applied to determine the optimal immobilization conditions for achieving the maximum enzyme activity. PPO immobilized on CTS/MMT (IPPO) and CTS-AuNPs/MMT (IPPO-Au) showed the highest enzyme activity at 15.61 × 103 and 29.01 × 103 U/g, respectively. IPPO-Au exhibited the higher stability and reusability than that of IPPO. The bio-catalytic performance of immobilized PPO was evaluated for the removal of phenol (PH), 4-chlorophenol (4-CP) and 2,4-dichlorophenol (2,4-DCP) in aqueous solution. The effects of pH, temperature, enzyme/substrate ratio, substrate concentration, reaction time on the phenolic compounds removal were investigated in detail. The results showed that, for both immobilized PPO, the optimal pH was 7, 6 and 5 for PH, 4-CP and 2,4-DCP, respectively, and the optimal temperature was 30 °C for all substrate. The optimal enzyme/substrate ratio and reaction time for IPPO-Au was lower than that of IPPO proved the higher catalytic efficiency. Chlorophenols showed the improved catalytic efficiency in comparison with PH for both immobilized PPO, while the effect of substrate chemical structure on the IPPO-Au properties was limited. The results suggested AuNPs presented in support played an important role on the enzyme activity and stability of immobilized PPO.

Biocomposites of polypyrrole, polyaniline and sodium alginate with cellulosic biomass: Adsorption-desorption, kinetics and thermodynamic studies for the removal of 2,4-dichlorophenol.

The biocomposites of polypyrrole (PPY), polyaniline (PANI) and sodium alginate (NaAlg) with cellulosic biomass barley husk (BH) were prepared and employed for the removal of 2,4-dichlorophenol (2,4-DCP) form aqueous media. The sorption of 2,4-DCP was studied using native and biocomposites (PPY/BH, PANI/BH and NaAlg/BH) as function of various process variables. The maximum sorption (qe, 7.55-24.57 mg/g) of 2,4-DCP was achieved in the range of 7-10 pH, 0.05 g composite dose, 25 mg/L initial concentration of 2,4-DCP and 120 min contact time at 30 °C. The FTIR analysis revealed the involvement of amino, hydroxyl and carboxylic groups for the binding of 2,4-DCP on the surface of biocomposites. The Freundlich and pseudo second order kinetics models best explained the 2,4-DCP adsorption on to the biocomposites. The ∆G, ∆H and ∆S parameters were also computed, which revealed the favorable and exothermic adsorption nature of 2,4-DCP. Presence of salts affected the 2,4-DCP adsorption negatively. HCl found to be efficient desorbing agent for 2,4-DCP from composites and up to 65.12% was eluted using 0.5 N solution. In view of promising efficiency, the biocomposites have potential to remove 2,4-DCP form industrial effluents.

Fabrication of iron-dipicolinamide catalyst with Fe-N bonds for enhancing non-radical reactive species under alkaline Fenton process.

Iron dipicolinamide (Fedpa), as an efficient Fenton-like catalyst, was fabricated to excite hydrogen peroxide (H2O2) for the removal of 2,4-dichlorophenol (2,4-DCP). The unique structures and the electronic properties of Fedpa were contributed to its excellent catalytic performance in alkaline Fenton process. Fe was chelated with dpa by four Fe-N bonds leaved two labile sites, which reduced the oxidation potential of dpa[FeIII/FeII], dpa[FeV/FeIII] or dpa[FeIV/FeII] to 0.316 V and 1.189 V respectively, and made it easily be bound with H2O2 to initiate the reaction. The results showed that 99.5% removal rate of 2,4-DCP (0.58 mM) was achieved by using 0.027 g/L Fedpa and 5.8 mM H2O2 in 60 min at pH 9.9. The coordination between Fe and dpa enhanced the catalytic efficiency of FeII. The active species generated in Fedpa/H2O2 system contained the iron-oxo species (dpaFeV = O or dpaIV = O), O2- and HO. The iron-oxo species was the main non-radical reactive species for the degradation of 2,4-DCP and some degradation intermediates were detected by GC-QTOF. Furthermore, the influence of factors, such as Fedpa loading, solution pH, temperature and anions (F-, Cl-, SO42-, NO3- and PO43-) on the catalytic performance of Fedpa were also discussed. This process of complexation between Fe and dpa combined with a green oxidant H2O2 presents a new insight for the use of Fenton-like system in the degradation of refractory organics.

Targeted live-cell nuclear delivery of the DNA 'light-switching' Ru(II) complex via ion-pairing with chlorophenolate counter-anions: the critical role of binding stability and lipophilicity of the ion-pairing complexes.

We have found recently that nuclear uptake of the cell-impermeable DNA light-switching Ru(II)-polypyridyl cationic complexes such as [Ru(bpy)2(dppz)]Cl2 was remarkably enhanced by pentachlorophenol (PCP), by forming ion-pairing complexes via a passive diffusion mechanism. However, it is not clear whether the enhanced nuclear uptake of [Ru(bpy)2(dppz)]2+ is only limited to PCP, or it is a general phenomenon for other highly chlorinated phenols (HCPs); and if so, what are the major physicochemical factors in determining nuclear uptake? Here, we found that the nuclear uptake of [Ru(bpy)2(dppz)]2+ can also be facilitated by other two groups of HCPs including three tetrachlorophenol (TeCP) and six trichlorophenol (TCP) isomers. Interestingly and unexpectedly, 2,3,4,5-TeCP was found to be the most effective one for nuclear delivery of [Ru(bpy)2(dppz)]2+, which is even better than the most-highly chlorinated PCP, and much better than its two other TeCP isomers. Further studies showed that the nuclear uptake of [Ru(bpy)2(dppz)]2+ was positively correlated with the binding stability, but to our surprise, inversely correlated with the lipophilicity of the ion-pairing complexes formed between [Ru(bpy)2(dppz)]Cl2 and HCPs. These findings should provide new perspectives for future investigations on using ion-pairing as an effective method for delivering other bio-active metal complexes into their intended cellular targets.

Fluorometric and colorimetric analysis of alkaline phosphatase activity based on a nucleotide coordinated copper ion mimicking polyphenol oxidase.

In this work, a fluorometric and colorimetric analysis of alkaline phosphatase (ALP) activity was developed based on nanozymes. The nanozymes were composed of nucleotides (ATP, ADP and AMP) coordinated with copper ions. All three kinds of nanozymes (ATP-Cu, ADP-Cu and AMP-Cu) exhibited polyphenol oxidase (PPO)-mimic activity by catalyzing a chromogenic reaction of 2,4-dichlorophenol (2,4-DP) and 4-aminoantipyrine (4-AP). However, there were obvious differences in the PPO-like activity and the fluorescence of the three nanozymes produced from the same concentration of nucleotides (keeping the concentration of Cu2+ unchanged at 5 mM). The catalytic activities of produced ADP-Cu and AMP-Cu were obviously higher than that of ATP-Cu at a certain nucleotide concentration of 3 mM. In addition, when ATP was hydrolyzed into ADP and AMP by ALP, more nanozymes were produced and the catalytic activity of the system was enhanced, which resulted in an obvious increase of the colorimetric signal. The signal intensity was proportional to ALP concentration in the range of 0-30 U L-1, and the detection limit for ALP was 0.3 U L-1 from the colorimetric detection. Moreover, the fluorescence intensity of the produced nanozymes was also proportional to the ALP concentration in the range of 1-30 U L-1 and the detection limit was 0.45 U L-1 from the fluorescence detection. A fluorometric and colorimetric sensing ALP method was thus established. The method showed a high selectivity for ALP activity compared with proteins, amino acids and other interference components. Furthermore, the proposed method was also used to detect ALP activity in human serum samples, which showed great potential for diagnostic and practical purposes.

What Are the Major Physicochemical Factors in Determining the Preferential Nuclear Uptake of the DNA "Light-Switching" Ru(II)-Polypyridyl Complex in Live Cells via Ion-Pairing with Chlorophenolate Counter-Anions?

Delivering potential theranostic metal complexes into preferential cellular targets is becoming of increasing interest. Here we report that nuclear uptake of a cell-impermeable DNA "light-switching" Ru(II)-polypyridyl complex can be significantly facilitated by chlorophenolate counter-anions, which was found, unexpectedly, to be correlated positively with the binding stability but inversely with the lipophilicity of the formed ion pairs.

Effect of O2, Ni0 coatings, and iron oxide phases on pentachlorophenol dechlorination by zero-valent iron.

This study explores the zero-valent iron (ZVI) dechlorination of pentachlorophenol (PCP) and its dependence on the dissolved oxygen (O2), presence/formation of iron oxides, and presence of nickel metal on the ZVI surface. Compared to the anoxic system, PCP dechlorination was slower in the presence of O2, which is a potential competitive electron acceptor. Despite O2 presence, Ni0 deposited on the ZVI surfaces catalyzed the hydrogenation reactions and enhanced the PCP dechlorination by Ni-coated ZVI bimetal (Nic/Fe). The presence of O2 led to the formation of passivating oxides (maghemite, hematite, lepidocrocite, ferrihydrite) on the ZVI and Nic/Fe bimetallic surfaces. These passive oxides resulted in greater PCP incorporation (sorption, co-precipitation, and/or physical entrapment with the oxides) and decreased PCP dechlorination in the oxic systems compared to the anoxic systems. As received ZVI comprised of a wustite film, and in the presence of O2, only ≈ 17% PCP dechlorination observed after 25 days of exposure with tetrachlorophenol being detected as the end product. Wustite remained as the predominant oxide on as received ZVI during the 25 days of reaction with PCP under oxic and anoxic conditions. ZVI acid-pretreatment resulted in the replacement of wustite with magnetite and enhanced PCP degradation (e.g. ≈ 52% of the initial PCP dechlorinated after 25 days under oxic condition) with accumulation of mixtures of tetra-, tri-, and dichlorophenols. When the acid-washed ZVI was rinsed in NiSO4/H2SO4 solution, Ni0 deposited on the ZVI surface and all the wustite were replaced with magnetite. After 25 days of exposure to the Nic/Fe, ≈ 78% and 97% PCP dechlorination occurred under oxic and anoxic conditions, respectively, producing predominantly phenol. Wustite and magnetite are respectively electrically insulating and conducting oxides and influenced the dechlorination and H2 production. In conclusion, this study clearly demonstrates that the dissolved oxygen present in the aqueous solution decreases the PCP dechlorination and increases the PCP incorporation when using ZVI and Nic/Fe bimetallic systems. The findings provide novel insights towards deciphering and optimizing the performance of complex ZVI and bimetallic systems for PCP dechlorination in the presence of O2.

Heterogeneous photo-Fenton process using iron-modified regional clays as catalysts: photonic and quantum efficiencies.

A regional raw clay was used as the starting material to prepare iron-pillared clays with different iron contents. The catalytic activity of these materials was tested in the heterogeneous photo-Fenton process, applied to the degradation of 2-chlorophenol chosen as the model pollutant. Different catalyst loads between 0.2 and 1.0 g L-1 and pH values between 3.0 and 7.0 were studied. The local volumetric rate of photon absorption (LVRPA) in the reactor was evaluated solving the radiative transfer equation applying the discrete ordinate method and using the optical properties of the catalyst suspensions. The photonic and quantum efficiencies of the 2-chlorophenol degradation depend on both the catalyst load and the iron content of the catalyst. The higher values for these parameters, 0.080 mol Einstein-1 and 0.152 mol Einstein-1, respectively, were obtained with 1.0 g L-1 of the catalyst with the higher iron content (17.6%). For the mineralization process, photonic and quantum efficiencies depend mainly on the catalyst load. Therefore, it was possible to employ a natural and cheap resource from the region to obtain pillared clay-based catalysts to degrade organic pollutants in water.