This work explored the potential application of an engineered biochar prepared from Mg-enriched tomato tissues to reclaim and reuse phosphate (P) from aqueous solution. Findings from batch sorption ...experiments suggested that, although sorption of P on the biochar was controlled by relatively slow kinetics, the maximum P sorption capacity of the biochar could reach >100 mg·g–1. Mathematical modeling and postsorption characterization results indicated that the sorption was mainly controlled by two mechanisms: precipitation of P through chemical reaction with Mg particles and surface deposition of P on Mg crystals on biochar surfaces. Most of the P retained in the engineered biochar was bioavailable and could be released equally at multiple successive extractions. In addition, the P-laden biochar significantly stimulated grass seed germination and growth. These results suggested the postsorption biochar can be cycled back directly to soils as an effective slow-release P-fertilizer.
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Although adsorbents can effectively remove phosphate from water, most are difficult to separate from water and their phosphate removal efficiencies are adversely affected by ...coexisting anions or humic acid. Here, a magnetic core–shell composite with Fe3O4 as the core and carbon as the shell (denoted as MFC) was functionalized with a metal–organic framework, UiO-66, and its phosphate adsorption ability was studied. The composite (denoted as MFC@UiO-66) was effectively separated from water within 1 min under an external magnetic field. The kinetics of phosphate adsorption onto MFC@UiO-66 was controlled by the intraparticle diffusion process, suggesting that the Zr in UiO-66 played an important role in phosphate adsorption. The isotherm for phosphate adsorption onto MFC@UiO-66 was well described by the Freundlich model. The adsorbent exhibited higher affinity toward phosphate than toward coexisting anions (e.g., Cl−, NO3−, and SO42−), reflecting high phosphate adsorption selectivity. The adsorption affinity of MFC@UiO-66 to phosphate increased with the increasing temperature, but decreased with increasing pH. The presence of dissolved humic acid negligibly affected phosphate adsorption onto MFC@UiO-66 because of its size-exclusion effects. The used adsorbent was easily regenerated with NaOH solution, and the sorbent displayed stable phosphate adsorption behavior after five regeneration cycles.
The low denitrification efficiency in constructed wetlands (CWs) was a crucial problem for treating the carbon-deficient wastewater. To further improve the N removal from the tailwater of wastewater ...treatment plant, the plant fermentation liquid (PFL, derived from wetland plant litter in our CWs) as a supplementary carbon source was used in horizontal subsurface-flow CW amended with Fe-modified biochar (FeB-HSCW) to increase the influent C/N ratio and drive the denitrification. The N removal performance of FeB-HSCW was investigated under various influent C/N ratios for achieving high-efficient N removal. The excellent removal rates of COD (89.35%), NO3−-N (97.48%), TN (93.76%), NH4+-N (>16%) and NO2−-N (>98%) were obtained in FeB-HSCW at the C/N of 9.0. When the large amount of PFL was added into the systems, the amount of 16S rRNA genes from bacteria and anammox bacteria, as well as of denitrification and anammox functional genes (narG, napA, nirS, nirK, qnorB, cnorB, nosZ-I, nosZ-II and hzsA) were statistically greater in FeB-HSCW than those in other two systems (C-HSCW, without biochar and FeB; B-HSCW, amended with biochar). However, the abundances of nitrification genes (amoA of AOA, amoA of AOB and nxrA) were the lowest in FeB-HSCW after adding the PFL. High-throughput analysis for 16S rRNA gene revealed that the PFL coupled with FeB remarkably optimized the structure of bacterial community. The FeB-HSCW added with sufficient PFL was enriched with the highest abundances of norank_p_Saccharibacteria, Bacillus, Geobacter, Pseudolabrys, Mizugakiibacter, Bradyrhizobium and norank_f_ Planctomycetaceae which were capable of autotrophic and/or heterotrophic denitrification as well as anammox, whereas the distribution of nitrifiers (Nitrospira) was the lowest. Overall, this work illustrated that the PFL coupled with FeB-HSCWwas a feasible and effective carbon self-sufficient HSCW for the high-efficient N removal from wastewater with low C/N ratio mainly via the autotrophic and heterotrophic denitrification and anammox.
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•PFL coupled with FeB-HSCW was a feasible and effective carbon self-sufficient CW.•High-efficient nitrogen removal was obtained in carbon self-sufficient FeB-HSCW.•Abundances of autotrophic and heterotrophic denitrifiers increased in this novel CW.•The anammox was significantly enhanced in carbon self-sufficient FeB-HSCW.•The nitrification was severely inhibited in carbon self-sufficient FeB-HSCW.
This study focused on students’ experience with a mobile multimedia application for a pronunciation course. An app was used for after-class pronunciation practice, through which the instructor gave ...out multimodal feedback to students. Student engagement with teacher feedback in the app was investigated from multiple data sources. Data collected in the form of the instructor’s response and analytics gathered through the mobile system revealed that students demonstrated a high level of engagement in the app, behaviorally, cognitively, and emotionally. Specifically, the instructor observed more submissions from and interactions with students compared with previous classes. Records of student-teacher interactions suggested that students reacted positively and actively to multimodal feedback from the teacher and expressed willingness to use the app for future learning. Questionnaire results further confirmed that a large number of the students perceived the app to be useful for practicing pronunciation tasks, as it made it easy for them to interact with the teacher, receive course materials, and submit recordings. Interviews among selected students revealed more details about students’ experiences and views. Some students reported accessing their peers’ readings and feedback from the teacher as a way of informing their own learning, which is made possible by the app. This study provides implications to enrich pronunciation instruction practice to maximize student engagement, which ultimately contributes to positive learning experiences and gains.
•Higher temperatures produced higher thermal stability biochars.•Production method showed strong effect on biochar properties.•Biochars showed no statistically significant effects on plant.
This work ...explored the effect of temperature, production method, and feedstock type on the physicochemical and biological properties of biochars and hydrochars. Biochars and hydrochars made at lower temperatures had higher production rates. Higher pyrolysis temperatures not only increased carbon content of biochars but also produced higher thermal stability biochars that did not start to decompose in air after 400–450°C. The production method showed strong effect on biochar properties. Compared to the dry-pyrolysis biochars derived from the same feedstocks, the hydrochars had more acidic pH values and lower carbon contents. The results showed that feedstock types could also influence characteristics of the biochars. None of the chars showed statistically significant effects on plant seed germination and seedling growth and thus could be used as soil amendments. Our findings indicated that biochars with different properties could be developed by changing production conditions to better satisfy their environmental applications.
Two biochars were produced from anaerobically digested and undigested sugar beet tailings through slow-pyrolysis at 600
°C. The digested sugar beet tailing biochar (DSTC) and raw sugar beet tailing ...biochar (STC) yields were around 45.5% and 36.3% of initial dry weight, respectively. Compared to STC, DSTC had similar pH and surface functional groups, but higher surface area, and its surface was less negatively charged. SEM-EDS and XRD analyses showed that colloidal and nano-sized periclase (MgO) was presented on the surface of DSTC. Laboratory adsorption experiments were conducted to assess the phosphate removal ability of the two biochars, an activated carbon (AC), and three Fe-modified biochar/AC adsorbents. The DSTC showed the highest phosphate removal ability with a removal rate around 73%. Our results suggest that anaerobically digested sugar beet tailings can be used as feedstock materials to produce high quality biochars, which could be used as adsorbents to reclaim phosphate.
•MDOM exhibited more HM binding sites than ADOM.•PARAFAC-derived components in MDOM had higher logKM values than those in ADOM.•Cu(II) exhibited stronger binding capacity than Zn(II) for both MDOM ...and ADOM.•More aromatic functional groups and binding sites accounted for high binding capacity.•2D-COS was a better approach than PARAFAC analysis for exploring HM–DOM interaction.
Enhanced knowledge on the binding of heavy metal (HM) with dissolved organic matter (DOM) is essential for understanding the toxicity and migration of HMs. In this study, two-dimensional correlation spectroscopy (2D-COS) and parallel factor (PARAFAC) analysis were combined to characterize the metal binding properties of DOMs, which were respectively extracted from macrophyte- and algal-dominant sediments (named MDOM and ADOM) in a eutrophic shallow lake. 2D absorption COS revealed that MDOM exhibited more HM binding sites (193, 195, 196, 199, 201, 203, 205, 207, 208, 212, 217nm) than ADOM (201, 205nm). PARAFAC analysis identified one protein- and two humic-like components from all titrated samples, with each component exhibiting different binding behaviors. The modified Stern–Volmer model showed that PARAFAC-derived components in MDOM had higher conditional stability constants (logKM) than in ADOM, suggesting that macrophyte-dominant sediments might play a more important role in the detoxification of HMs. Meanwhile, low binding abilities of Zn(II)-DOM complexes indicated that the toxicity of zinc in eutrophic lakes should not be overlooked. More aromatic functional groups and binding sites were suggested to be responsible for the high binding ability. 2D-COS was a better approach than PARAFAC analysis for exploring HM–DOM interaction.
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•The quantitative role of EPS matrix in Microcystis aggregation and bloom formation was studied.•The aggregation potential of Microcystis samples decreased by 27.6–57.4% after EPS ...extraction.•Increased energy barrier and second energy minimum accounted for the deteriorated aggregation.•The predominant energy contribution transformed from TB-EPS to LB-EPS during the bloom formation.•A conceptual model about EPS function in Microcystis aggregation and bloom formation was proposed.
The development of mucilaginous cyanobacterial Microcystis blooms is a serious environmental and ecological problem, and information on the bloom-formation mechanism has been lacking until now. The aggregation of microbial cells was attributed to the matrix of extracellular polymeric substances (EPS). In this study, the quantitative role of EPS matrix in Microcystis aggregation and mucilaginous bloom formation was investigated. The results showed that when EPS matrix was extracted, the aggregation abilities decreased by 27.6% and 57.4% for the lab-cultured Microcystis suspension and the field-sampled Microcystis aggregates, respectively. The extended DLVO theory revealed that EPS extraction increased the energy barrier and the values of the second energy minimum, which accounted for the deteriorated aggregation. Further analysis showed an increasing attraction energy of EPS matrix during the Microcystis bloom development, whereas the predominant contribution originated from tightly bound EPS (TB-EPS) and loosely bound EPS (LB-EPS) for the lab-cultured and field-sampled Microcystis samples. The heterogeneous energy contribution of EPS subfractions was found to be associated with the variations in organic contents. Specifically, Microcystis aggregates exhibited a higher organic content of TB-EPS than of LB-EPS compared with the lab-cultured Microcystis suspension, whereas organic content in only the LB-EPS fraction for the bloom samples was significantly higher (p<0.01) than that of the Microcystis aggregates. Based on these results, a conceptual model of EPS function was proposed in which TB-EPS plays an important role in the formation of Microcystis aggregates, after which LB-EPS contributed to the subsequent development from Microcystis aggregates to mucilaginous bloom formation.
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•Fifty-seven transformation products were identified from sixty parent compounds in wastewater.•Forty percentage of transformation products had higher concentration than their ...parents.•Half of identified TPs had higher predicted toxicity than their parents.•Twenty identified TPs have not been reported in previous study.
Pesticides and pharmaceuticals are widely used in modern life and are discharged into wastewater after usage. However, a large number of transformation products (TPs) are formed through abiotic (hydrolysis/photolysis, etc.) and biotic (aerobic/anaerobic degradation by micro-organisms) wastewater treatment processes, and the structure and potential risk of TPs are still unclear. In this study, a suspect and non-target screening was performed to monitor these chemicals with HPLC-QTOF-MS. We identified 60 parent compounds by suspect screening in three Chinese wastewater treatment plants with the commercial database of pesticides and pharmaceuticals, and they were confirmed by authentic standards. Then, suspect and non-target screening strategies based on the predicted diagnostic fragment ions were used to screen TPs of the 60 parent compounds. We tentatively identified 50 TPs and confirmed thirteen of them with authentic standards. Among 13 quantified TPs, about 40% of them showed higher concentration than their parent compounds in effluent. Especially, cloquintocet, as a TP of cloquintocet-mexyl, had a concentration ratio TP/parent = 14,809 in effluent. Twenty-five TPs had higher predicted toxicity than the corresponding parent compounds by calculating their LC50 values towards aquatic organisms using toxicity prediction software. Twenty identified TPs were firstly reported in this study. These results indicate the importance of TP analysis in environmental monitoring in wastewater.
Highly dispersed ZrO2 particles confined in the MIL-101 (denoted as MIL-101@Zr(DS)) with varied ZrO2 loading amounts were prepared by the double solvents method. For comparison, ZrO2 loaded MIL-101 ...samples were synthesized by the conventional impregnation method (denoted as MIL-101@Zr(I)) and the deposition method (denoted as MIL-101@Zr(D)). The characterization results indicated that for MIL-101@Zr(DS), ZrO2 particles were dominantly confined in MIL-101 with a much higher dispersion as compared with MIL-101@Zr(I) and MIL-101@Zr(D). The maximum phosphate adsorption capacity and ZrO2 content normalized phosphate adsorption capacity of the MIL-101@Zr(DS) were 21.28 mg P·g−1 and 1120.0 mg P·g−1, respectively. Additionally, the ZrO2 content normalized phosphate adsorption capacity was significantly larger than that for MIL-101@Zr(I) and MIL-101@Zr(D) as well as the reported values for other Zr-based adsorbents. The effects of solution chemistry on phosphate adsorption to MIL-101@Zr(DS), MIL-101@Zr(I) and MIL-101@Zr(D) were also examined. Compared with MIL-101@Zr(I) and MIL-101@Zr(D), the adsorption of phosphate on MIL-101@Zr(DS) was less affected by the coexistence of anions and dissolved humic acid. Increasing pH from 3 to 12 led to decreased phosphate adsorption capacity of MIL-101@Zr(DS) from 10.38 mg P·g−1 to 2.03 mg P·g−1. Accordingly, used MIL-101@Zr(DS) could be effectively regenerated under alkaline conditions and exhibited stable adsorption-desorption performance.
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•ZrO2 nanoparticles confined in MIL-101 was first prepared by double solvents method.•ZrO2 was dispersed at molecular level in MIL-101 pores due to the confinement effect.•ZrO2-loaded MIL-101 had an extraordinarily high efficiency for phosphate adsorption.
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