Oxidation of phthalate acid esters using hydrogen peroxide and polyoxometalate/graphene hybrids

Huge Electron Sponge of Polyoxometalate toward Advanced Lithium-Ion Storage

The huge polyoxometalate, N a 48 [ H x M o 256 V I M o 112 V O 1032 ( H 2 O ) 240 ( SO 4 ) 48 ] ({Mo368}), which can be prepared by a facile solution process and can be applied in lithium-ion storage applications as the anode. The large and open hollow nanostructure is promising to store a larger number of lithium ions and expedite the diffusion of lithium ions. A single {Mo368} nanocluster can transfer 624 electrons, referred to as a "huge electron sponge". Pure {Mo368} without any support materials exhibits very high capacities of 964 mA h g-1 with hardly any decay for 100 cycles at 0.1 A g-1 and still maintains 761 mA h g-1 after 180 cycles at 0.5 A g-1, indicating great cycling stability. The {Mo368} anode provides excellent rate performance and reversibility during the lithiation/delithiation processes, which are contributed by both the diffusion-controlled process and the capacitive process. The capacitive contribution can reach 71.7% at a scan rate of 2 mV s-1. The high DLi+ value measured by GITT confirms the fast reaction kinetics of the {Mo368} electrode. The {Mo368}//NCM111-A full cell is practically applied to light LED lamps. These investigations indicate that {Mo368} nanoclusters are advanced energy storage materials with high capacities, fast charge transfer, and low-cost mass production for lithium-ion storage. Moreover, {Mo368} should be considered a clean energy material because there is no production of environmental pollution during the charge/discharge processes.

Point-of-Use SERS Approach for Efficient Determination and Removal of Phthalic Acid Esters Based on a Metal-Organic Framework-Coated Melamine Sponge

Phthalic acid esters (PAEs) are ubiquitous environmental contaminants, and their real-time monitoring and removal remain challenging. Herein, a point-of-use (POU) device integrating adsorption, surface-enhanced Raman spectroscopy (SERS), and removal strategy was developed and realized ultrafast on-site determination of PAEs and cleanup of them from water. A piece of flexible melamine sponge (MS) was coated with gold nanostars (AuNSs) and metal-organic frameworks (MOFs), thus obtaining SERS activity and adsorption capacity. Based on this multifunctional AuNSs@MOFs/MS composite, clear trends were observed between SERS signal intensity and concentration of di(2-ethylhexyl)phthalate (DEHP) and dibutyl phthalate (DBP). The method detection limits of DEHP and DBP were calculated to be 0.75 × 10-7 and 0.67 × 10-7 M in water, respectively, proving good sensitivity. Furthermore, this POU device exhibited satisfactory adsorption capacity (∼82.3 g/g for DBP and ∼90.0 g/g for DEHP), high adsorption efficiency (equilibrium in 100 s), and good regeneration capability (removal efficiency >70% after 5 cycles). The applicability of this device was verified by its good determination and removal performance in real environmental water matrices. The whole process could be completed within 5 min. This approach provides a new POU alternative for real-time monitoring and removal of PAEs in water.

Tunable zirconium-based metal organic frameworks synthesis for dibutyl phthalate efficient removal: An investigation of adsorption mechanism on macro and micro scale

The tunable porous structure of metal organic frameworks (MOFs) plays a crucial role in determining their adsorption performance. In this study, we developed and employed a strategy involving monocarboxylic acid assistance to synthesize a series of zirconium-based MOFs (UiO-66-F4) for the removal of aqueous phthalic acid esters (PAEs). The adsorption mechanisms were investigated by combining batch experiments, characterization and theoretical simulation. By adjusting the affecting factors (i.e., initial concentration, pH values, temperature, contact time and interfering substance), the adsorption behavior was confirmed as a spontaneous and exothermic chemisorption process. The Langmuir model provided a good fit, and the maximum expected adsorption capacity of di-n-butyl phthalate (DnBP) on UiO-66-F4(PA) was calculated to be 530.42 mg·g-1. Besides, through carrying out the molecular dynamics (MD) simulation, the multistage adsorption process in the form of DnBP clusters was revealed on a microcosmic scale. The independent gradient model (IGM) method showed the types of weak interactions of inter-fragments or between DnBP and UiO-66-F4. Furthermore, the synthesized UiO-66-F4 displayed excellent removal efficiency (>96 % after 5 cycles), satisfactory chemical stability and reusability in the regeneration process. Hence, the modulated UiO-66-F4 will be regarded as a promising adsorbent for PAEs separation. This work will provide referential significance in tunable MOFs development and actual applications of PAEs removal.

Di-n-butyl phthalate stress induces changes in the core bacterial community associated with nitrogen conversion during agricultural waste composting

Nitrogen (N) loss during composting reduces the quality of compost products and causes secondary environmental pollution. Phthalate esters (PAEs) are common pollutants in agricultural wastes. However, little information is currently available on how PAEs affect N conversion during agricultural waste composting. This research systematically analyzed the impact of di-n-butyl phthalate (DBP) pollution on the N conversion and its related microbial community during composting. Our results indicated that DBP stress results in a shorter thermophilic phase, and then slower compost maturation during composting. Notably, DBP stress inhibited the conversion of ammonia to nitrate, but increased the release of NH₃ and N₂O leading to an increased N loss and an elevated greenhouse effect. Furthermore, DBP exposure led to a reduction of bacteria related to NH₄⁺ and NO₃^- conversion and altered the network complexity of the bacterial community involved in N conversion. It also reduced the abundance of a major nitrification gene (amoA) (P < 0.01) and increased the abundance of denitrification genes (nirK and norB) (P < 0.05). Moreover, DBP affected the overall microbial community composition at all tested concentrations. These findings provide theoretical and methodological basis for improving the quality of PAE-contaminated agricultural waste compost products and reducing secondary environmental pollution.

Improving the activity and expression level of a phthalate-degrading enzyme by a combination of mutagenesis strategies and strong promoter replacement

Phthalic acid esters (PAEs) are widely used plasticizers found in consumer products, which enter the environment and pose severe threats to human health. Here, a new PAE-degrading enzyme EstJ6 was modified by combining mutagenesis strategies and a strong promoter replacement to improve its catalytic activity and expression level. Four mutants with enhanced activity were obtained by random mutation, among which EstJ6M1.1 exhibited the highest catalytic activity with an increase in catalytic activity by 2.9-fold toward dibutyl phthalate (DBP) than that of the wild-type (WT) enzyme. With these mutants as a template, a variant EstJ6M2 with 3.1-fold higher catalytic activity and 4.61 times higher catalytic efficiency (Kcat/Km) was identified by staggered extension PCR. Targeting four mutation sites of EstJ6M2, a variant EstJ6M3.1 was gained by site-directed saturation mutagenesis and displayed 4.3-fold higher activity and 5.97 times higher Kcat/Km than WT. The expression level of three mutants EstJ6M1.1, EstJ6M2, and EstJ6M3.1, as well as the WT, increased nearly threefold after a strong promoter replacement. These results provide a proof-theoretical basis and practicable pipeline for applying PAE-degrading enzymes.

Degradation and Detection of Endocrine Disruptors by Laccase-Mimetic Polyoxometalates

Endocrine disruptors are newly identified water contaminants and immediately caught worldwide concern. An effort has been made to degrade endocrine disruptors in the water body by relying on laccase-assisted approaches, including laccase-mediated catalytic systems, immobilized laccase catalytic systems, and nano-catalytic systems based on atypical protein enzymes. Analogous to laccases, polyoxometalates (POMs) have a similar size as these enzymes. They are also capable of using oxygen as an electron acceptor, which could assist the removal of endocrine disruptors in water. This perspective begins with a brief introduction to endocrine disruptors and laccases, summarizes current approaches employing laccases, and focuses on the nano-catalytic systems that mimic the function of laccases. Among the inorganic nanoparticles, POMs meet the design requirements and are easy for large-scale production. The catalytic performance of POMs in water treatment is highlighted, and an example of using polyoxovanadates for endocrine disruptor degradation is given at the end of this perspective. Exploring laccase-mimetic POMs will give key insights into the degradation of emergent water contaminants.