Pseudocapacitive Behaviors of Polypyrrole Grafted Activated Carbon and MnO2 Electrodes to Enable Fast and Efficient Membrane-Free Capacitive Deionization.

Capacitive deionization (CDI) has emerged as a promising technique for brackish water desalination. Here, composites of polypyrrole grafted activated carbon (Ppy/AC) were prepared via in situ chemical oxidative polymerization of pyrrole on AC particles. The Ppy/AC cathode was then coupled with a MnO2 anode for desalination in a membrane-free CDI cell. Both the Ppy/AC and MnO2 electrodes exhibited pseudocapacitive behaviors, which can selectively and reversibly intercalate Cl- (Ppy/AC) and Na+ (MnO2) ions. Compared to AC electrodes, the specific capacitances of Ppy/AC electrodes increased concurrently with the pyrrole ratios from 0 to 10%, while the charge transfer and ionic diffusion resistances decreased. As a result, the 10%Ppy/AC-MnO2 cell showed a maximum salt removal capacity of 52.93 mg g-1 (total mass of active materials) and 34.15 mg g-1 (total mass of electrodes), which was higher than those of conventional, membrane, and hybrid CDI cells. More notably, the salt removal rate of the 10%Ppy/AC-MnO2 cell (max 0.46 mg g-1 s-1 to the total mass of active materials and 0.30 mg g-1 s-1 to the total mass of electrodes) was nearly 1 order of magnitude higher than those in most previous CDI studies, and this fast and efficient desalination performance was stabilized over 50 cycles.

Reduced Lattice Constant in Al-Doped LiMn2O4 Nanoparticles for Boosted Electrochemical Lithium Extraction.

Extracting lithium selectively and efficiently from brine sources is crucial for addressing energy and environmental challenges. The electrochemical system employing LiMn2O4 (LMO) electrodes has been recognized as an effective method for lithium recovery. However, the lithium selectivity and stability of LMO need further enhancement for its practical applications. Herein, the Al-doped LMO with reduced lattice constant is successfully fabricated through a facile one-step solid-state sintering method, leading to enhanced lithium selectivity. The reduced lattice constant in Al-doped LMO is proved through spectroscopic analyses and theoretic calculations. Compared to the original LMO, the Al-doped LMO (LiAl0.05Mn1.95O4, LMO-Al0.05) exhibits highercapacitance, lower resistance, and improved stability. Moreover, the LMO-Al0.05 with reduced lattice constant can offer higher Li+ diffusion coefficient and lower intercalation energy revealed by cyclic voltammetry and multiscale simulations. When employed in hybrid capacitive deionization (CDI), the LMO-Al0.05 obtains a Li+ intercalation capacity of 21.7 mg g-1 and low energy consumption of 2.6 Wh mol-1 Li+. Importantly, the LMO-Al0.05 achieves a high Li+ extraction percentage (≈86%) with Li+/Na+ and Li+/Mg2+ selectivity of 1653.8 and 434.9, respectively, in synthetic brine. The results demonstrate that the Al-doped LMO with reduced lattice constant could be a sustainable solution for electrochemical lithium extraction.

Boosted simultaneous removal of chlortetracycline and Cu (II) by Litchi Leaves Biochar: Influence of pH, ionic strength, and background electrolyte ions.

The coexistence of heavy metals and antibiotics in the environment always results in greater toxicity compared to the individual precursors. Therefore, efficient and economic technology for the simultaneous removal of antibiotics and heavy metals is essential. Herein, litchi leaves biochar carbonized at 550 °C (L550) demonstrated high efficiency in co-removal of CTC (1838.1 mmol/kg) and Cu (II) (1212.9 mmol/kg) within wide range of pH (pH 4-7). Ionic strength obviously enhanced the Cu (II) removal but showed no significant effect on CTC removal. Although Al3+ and HPO42- decreased the adsorption capacities of CTC and Cu (II) on L550, the coexistence of Na+, K+, Mg2+, Cl-, NO3-, CO32- and SO42- showed a negligible effect on the simultaneous removal of CTC and Cu (II). Moreover, the adsorption capacities of CTC and Cu (II) on L550 were excellent in the river water, tap water, and lake water. In addition to electrostatic interactions, ion exchange governed Cu (II) adsorption, while surface complexation played a key role in CTC adsorption on L550. Our results demonstrated that litchi leaves biochar could be a promising adsorbent for remediating multi-contaminated environments.

Boosted brackish water desalination and water softening by facilely designed MnO2/hierarchical porous carbon as capacitive deionization electrode.

Capacitive deionization (CDI) is a promising technique for brackish water desalination. However, its salt electrosorption capacity is insufficient for practical application yet, and little information is available on hardness ion (Mg2+, Ca2+) removal in CDI. Herein, hierarchical porous carbon (HPC) was prepared from low-cost and renewable microalgae via a simple one-pot approach, and both MnO2/HPC and polyaniline/HPC (PANI/HPC) composites were then synthesized using a facile, one-step hydrothermal method. Compared with the MnO2 electrode, the MnO2/HPC electrode presented an improved hydrophilicity, higher specific capacitance, and lower electrode resistance. The electrodes exhibited pseudocapacitive behaviors, and the maximum salt electrosorption capacities of MnO2/HPC-PANI/HPC CDI cell was up to 0.65 mmol g-1 NaCl, 0.71 mmol g-1 MgCl2, and 0.76 mmol g-1 CaCl2, respectively, which were comparable and even higher than those of the previously reported CDI cells. Additionally, the MnO2/HPC electrode presented a selectivity order of Ca2+ ≥ Mg2+ > Na+, and the divalent cation selectivity was found to be attributed to their stronger binding strength in the cavity of MnO2. Multiscale simulations further reveal that the MnO2/HPC electrodes with the unique luminal configuration of MnO2 and HPC as supportive framework could offer a great intercalation selectivity of the divalent cations and exhibit a great promise in hardness ion removal.

Facile Designed Manganese Oxide/Biochar for Efficient Salinity Gradient Energy Recovery in Concentration Flow Cells and Influences of Mono/Multivalent Ions.

Development of effective, environmentally friendly, facile large-scale processing, and low-cost materials is critical for renewable energy production. Here, MnOx/biochar composites were synthesized by a simple pyrolysis method and showed high performance for salinity gradient (SG) energy harvest in concentration flow cells (CFCs). The peak power density of CFCs with MnOx/biochar electrodes was up to 5.67 W m-2 (ave. = 0.91 W m-2) and stabilized for 500 cycles when using 1 and 30 g L-1 NaCl, which was attributed to their high specific capacitances and low electrode resistances. This power output was higher than all other reported MnO2 electrodes for SG energy harvest due to the synergistic effects between MnOx and biochar. When using a mixture with a molar fraction of 90% NaCl and 10% KCl (or Na2SO4, MgCl2, MgSO4, and CaCl2) in both feed solutions, the peak power density decreased by 2.3-40.1% compared to 100% NaCl solution with Ca2+ and Mg2+ showing the most pronounced negative effects. Our results demonstrated that the facile designed MnOx/biochar composite can be used for efficient SG energy recovery in CFCs with good stability, low cost, and less environmental impacts. When using natural waters as the feed solutions, pretreatment would be needed.

Effects of biochar application with fertilizer on soil microbial biomass and greenhouse gas emissions in a peanut cropping system.

This study investigated the effects of biochar application with organic or mineral fertilizers on soil microbial biomass, and associated emissions of CO2 and CH4 under field settings planted with peanut. The results indicated that physicochemical properties of soil were improved under biochar application. Soil microbial biomass carbon (MBC) was significantly increased with the application of biochar plus organic fertilizer compared to that of organic fertilizer only, but no significant difference of MBC was found between the treatment under biochar application plus mineral fertilizer and that under mineral fertilizer only. Biochar application did not affect the amount of microbial biomass nitrogen (MBN) with either mineral or organic fertilizer. The cumulative CO2 emission did not change under biochar application, while the cumulative CH4 emission was significantly decreased (p < 0.05) by 68.67% on average with the application of organic fertilizer plus biochar compared to that of organic fertilizer only. When biochar was applied in combination with either mineral or organic fertilizer, both the net global warming potential (GWP) and the greenhouse gas intensity (GHGI) were significantly decreased compared to that without biochar amendment. In all, biochar can improve soil quality, and enhance soil carbon sequestration as well as peanut yields.

Mo2N nanobelt cathodes for efficient hydrogen production in microbial electrolysis cells with shaped biofilm microbiome.

High cost platinum (Pt) catalysts limit the application of microbial electrolysis cells (MECs) for hydrogen (H2) production. Here, inexpensive and efficient Mo2N nanobelt cathodes were prepared using an ethanol method with minimized catalyst and binder loadings. The chronopotentiometry tests demonstrated that the Mo2N nanobelt cathodes had similar catalytic activities for H2 evolution compared to that of Pt/C (10 wt%). The H2 production rates (0.39 vs. 0.37 m3-H2/m3/d), coulombic efficiencies (90% vs. 77%), and overall hydrogen recovery (74% vs. 70%) of MECs with the Mo2N nanobelt cathodes were also comparable to those with Pt/C cathodes. However, the cost of Mo2N nanobelt catalyst ($ 31/m2) was much less than that of Pt/C catalysts ($ 1930/m2). Furthermore, the biofilm microbiomes at electrodes were studied using the PacBio sequencing of full-length 16S rRNA gene. It indicated Stenotrophomonas nitritireducens as a putative electroactive bacterium dominating the anode biofilm microbiomes. The majority of dominant species in the Mo2N and Pt/C cathode communities belonged to Stenotrophomonas nitritireducens, Stenotrophomonas maltophilia, and Comamonas testosterone. The dominant populations in the cathode biofilms were shaped by the cathode materials. This study demonstrated Mo2N nanobelt catalyst as an alternative to Pt catalyst for H2 production in MECs.

Comparison of biochar- and activated carbon-supported zerovalent iron for the removal of Se(IV) and Se(VI): influence of pH, ionic strength, and natural organic matter.

Biochar (BC) and activated carbon (AC) were both produced from corn straw. Biochar-supported zerovalent iron (BC-ZVI) and activated carbon-supported zerovalent iron (AC-ZVI) were synthesized and applied for Se(IV)/Se(VI) removal. The sorption capacity of BC-ZVI for Se(IV) and Se(VI) was reported at 62.52 and 35.39 mg g-1, higher than that of AC-ZVI (56.02 and 33.24 mg g-1), respectively, due to its higher iron content and more positive charges. The spectroscopic analyses showed that Se(IV)/Se(VI) were reduced to Se(0)/Se(-II) of less toxicity and solubility. The effects of various factors such as pH, ionic strength, co-existing cations and anions, and natural organic matter (NOM) were also investigated. Ionic strength showed no significant effect on Se(IV)/Se(VI) removal, but pH was critical. The presence of NO3- and SO42- did not cause obvious inhibition to the removal, while PO43- inhibited the sorption capacity of BC-ZVI and AC-ZVI for Se(IV)/Se(VI) significantly. Common cations (K+, Ca2+, and Mg2+) were found to slightly enhance the removal, while NOM significantly decreased the sorption capacity of BC-ZVI and AC-ZVI for Se(IV)/Se(VI). Besides, NOM showed stronger inhibition effect on AC-ZVI than that on BC-ZVI. These results indicated that BC-ZVI, compared with AC-ZVI, could be a promising sorbent to remove Se(IV)/Se(VI) due to its low cost and high efficiency.

Biochar amendment with fertilizers increases peanut N uptake, alleviates soil N2O emissions without affecting NH3 volatilization in field experiments.

Biochar application to soil is currently widely advocated for a variety of reasons related to sustainability. However, the synergistic effects of biochar combined with mineral or organic fertilizer on soil N2O emissions, NH3 volatilization, and plant N uptake are poorly documented. Field plot experiments planted with peanut were conducted under the application of biochar (derived from rice husk and cottonseed husk, 50 t ha-1) with organic or mineral fertilizer. It was found that biochar increased soil nutrient availability and decreased surface soil bulk density, demonstrating that biochar could improve the soil quality especially in the 0-20-cm profile. The total N content of the plant changed little with treatments, but the kernel N concentration increased significantly when biochar was applied with organic fertilizer. Peanut yield increased with biochar amendment while no significant difference was observed in plant biomass, suggesting biochar had a positive effect on belowground biomass. Peanut N uptake was also increased following biochar amendment with either organic or mineral fertilizers. While biochar amendment had no significant effect on soil NH3 volatilization, it did decrease the cumulative N2O emission by 36.3% on average with organic fertilizer, and by 32.6% with mineral fertilizer, respectively (p < 0.05). The copy numbers of 16S rDNA, nifH, nirK, and nirS were not influenced by the application of biochar; however, the copy number of nosZ was significantly increased under biochar plus mineral fertilizer treatment. The results imply that biochar application can suppress N2O emissions, as a result of abiotic factors and enhanced peanut N uptake rather than changes of denitrification genes.

Enhanced power generation and wastewater treatment in sustainable biochar electrodes based bioelectrochemical system.

Corn-straw biochar (BC500 and BC900) and KOH modified biochar (BAC) were used as the electrode materials of bioelectrochemical system (BES). Compared to carbon felt (CF) electrodes BES, the maximum power density of BC500, BC900 and BAC anodes BES increased by 10.7%, 56.0% and 92.0%, and that of BC500, BC900 and BAC cathodes BES increased by 3.1, 5.2 and 4.8 times, respectively. The CF electrodes BES was optimized to decolor the AO7 simulated wastewater and 97% of AO7 was quickly degraded within 2h. When using biochar anodes, the decoloration rates were enhanced. The apparent rate constant (kapp) increased from 2.93h-1 for CF anode BES to 3.58, 4.35 and 5.33h-1 for BC500, BC900 and BAC anode system, respectively. AO7 could also be effectively decolored in biochar cathode systems, which was mainly due to adsorption.

Sorption of mercury (II) and atrazine by biochar, modified biochars and biochar based activated carbon in aqueous solution.

Corn straw biochar (BC) was used as a precursor to produce Na2S modified biochar (BS), KOH modified biochar (BK) and activated carbon (AC). Experiments were conducted to compare the sorption capacity of these sorbents for aqueous Hg (II) and atrazine existed alone or as a mixture. In comparison to BC, the sorption capacity of BS, BK and AC for single Hg (II) increased by 76.95%, 32.12% and 41.72%, while that for atrazine increased by 38.66%, 46.39% and 47 times, respectively. When Hg (II) and atrazine coexisted in an aqueous solution, competitive sorption was observed on all these sorbents. Sulfur impregnation was an efficient way to enhance the Hg (II) removal due to the formation of HgS precipitate, and oxygen-containing functional groups on the sorbents also contributed to Hg (II) sorption. Activated carbon was the best sorbent for atrazine removal because of its extremely high specific surface area.

Effects of lead concentration and accumulation on the performance and microbial community of aerobic granular sludge in sequencing batch reactors.

The present study investigated the effects of lead on the morphological structure, physical and chemical properties, wastewater treatment performance and microbial community structure of aerobic granular sludge (AGS) in sequencing batch reactors (SBRs). The results showed that at Pb(2+) concentration of 1 mg/L, the mixed liquid suspended solids decreased, the settling velocity increased and the sludge volume index increased sharply. Meanwhile, AGS began to disintegrate and show an irregular shape. In terms of wastewater treatment in an SBR, the phosphorus removal rate was affected only until the Pb(2+) concentration was up to 1 mg/L. The [Formula: see text] removal efficiency began to decline when the Pb(2+) concentration increased to 6 mg/L, while the removal of chemical oxygen demand increased slightly within the Pb(2+) concentration range of 1-6 mg/L. Significant changes were observed in the microbial community structure, especially the dominant bacteria. Compared to the Pb(2+) accumulation on the sludge, the Pb(2+) concentration in the aqueous phase played a more important role in the performance and microbial community of AGS in SBRs.

Influence of biochar on sorption, leaching and dissipation of bisphenol A and 17α-ethynylestradiol in soil.

Biochar, as a soil amendment, provided a very cost-effective, convenient route to dispose organic residues. In the present study, the impact of adding biochar on the sorption, leaching and dissipation processes of bisphenol A (BPA) and 17α-ethynylestradiol (EE2) in soil was investigated. The biochar derived from corn stalks at 500 °C for 1.5 h was characterized by a highly aromatic and microporous structure with various functional groups on the surface. In the batch sorption studies, the application of 4 wt% biochar to soil significantly increased the solid-water distribution coefficients by 263% for BPA and by 298% for EE2 at the pollutant equilibrium concentration of 0.01 mg L(-1). In the leaching experiment, after five leaching periods, soil amended with 1 wt%, 2 wt% and 4 wt% biochar reduced the cumulative amount by 19%, 28% and 53% for BPA, 42%, 58% and 77% for EE2 compared to the biochar-free soil. Interestingly, during the 90 d incubation experiment, BPA and EE2 dissipations were not significantly affected by the added biochar, while remarkable decreases of CaCl2 extractable BPA and EE2 were observed. The overall results highlighted the distinctive potential of this biochar in reducing the mobility of BPA and EE2 in soil, meanwhile without attenuating the degradation of the two pollutants.