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Mechanism studies in aqueous/nonaqueous solution are summarized. Electrode engineering on NOxRR-to-NH3 in aqueous solution is generalized. Electrolyte modifications strategies are analyzed towards operation conditions and electrolyte choosen.

Hybrid strategy of utilizing large solar thermal input overlaid with solar electricity for continuous wastewater purification without any catalyst.

Camellia oleifera is a high quality woody oilseed crop that produces a low yield in the central subtropics of China. Although fertilization can efficiently increase C. oleifera yield in these areas, the influences of fertilization continuously on soil microbiota and soil fertility remain poorly understood. The purpose of this study was to determine the influences of the type and amount of fertilizer on the soil properties of C. oleifera. Here, we compared the effects of organic fertilizer, organic–inorganic compost, no fertilizer control, and low (F1), medium (F2), and high (F3) amounts of continuously applied organic–inorganic compost at the sapling stage All chemical indicators and copiotropic bacteria measured were significantly lower in organic fertilizer and without fertilizer. Successive fertilization over two years with organic-inorganic compost significantly altered the relative abundance of the dominant bacterial groups at the phylum levels. the abundance of these phyla was the same in F2 and F3 treatments which was higher than their abundance in the other treatments. The relative abundance of kopiotrophic bacteria, especially proteobacteria and gemmatimonadetes, increased significantly and similarly with F2 and F3 treatments. With successive fertilizations, the levels of total nitrogen (TN), total phosphorus (TP) and organic matter (OM) were the vital factors affecting bacterial communities, which was confirmed by structural equation models, redundant analyzes and random forest models. These results suggest that the continuous application of moderate amounts of organic-inorganic compost is the main driver for the improvement of soil bacterial communities, and this was mainly achieved by altering the levels of OM, TN and TP, thus affecting the copiotropic bacterial abundance. This study provides a scientific basis for optimal fertilization of C. oleifera forest.

Mg–Li based alloys have been widely used in various fields. However, the widespread use of Mg–Li based alloys were restricted by their poor properties. The addition of rare earth element in Mg–Li can significantly improve the properties of alloys. In the present work, different electrochemical methods were used to investigate the electrochemical behavior of Y(III) on the W electrode in LiCl–KCl melts and LiCl–KCl–MgCl2 melts. In LiCl–KCl melts, typical cyclic voltammetry was used to study the electrochemical mechanism and thermodynamic parameters for the reduction of Y(III) to metallic Y. In LiCl–KCl–MgCl2 melts, the formation mechanism of Mg–Y intermetallic compounds was investigated, and the results showed that only one kind of Mg–Y intermetallic compound was formed under our experimental conditions. Mg–Li–Y alloys were prepared via galvanostatic electrolysis, and XRD and SEM equipped with EDS analysis were used to analyze the samples. Because of the restrictions of EDS analysis, ICP-AES was used to analyze the Li content in Mg–Li–Y alloys. The microhardness and Young's modulus of the Mg–Li–Y alloys were then evaluated.

Full mineralization of organic pollutants is a tough task with existing technologies. Even if all conventional energies and extremes are exhausted, high-temperature wastewater treatment is not worth the loss from the perspective of energy. Solar engineering holds promise for the full mineralization of organic pollutants to tackle the global fossil energy shortage. Here, we report solar engineering for full mineralization and efficient solar utilization. The solar energies and spectrum were fully utilized to initiate the solar heat and solar electricity. Two energies were applied to trigger the thermochemical and electrochemical oxidation of the organic pollutants. Our study bridges the gap between the energy and environment towards efficient solar utilization and effective water treatment. As a proof-of-concept study, this demonstrates a solar engineering of full phenol mineralization in wastewater. A record phenol mineralization rate was achieved to reach an oxidation rate of 98% and COD of 93% under a constant current density of 50mA/cm2 at 150°C. UV and HPLC were used to detect the intermediate products during variable time intervals. The results showed that the intermediate products are composed of maleic acid, hydroquinone and p-benzoquinone. In the extreme high temperature (90°C), the solar oxidation time and pathway are greatly altered. The reaction rate constant at 150°C is about 11 times than that at 90°C. More solar heat significantly reduces the activated energy of the pollutant oxidation and lowers the potential of electrolysis.

Long-term and high-intensity application of inorganic fertilizer leads to a strong variation of soil characteristics. The changes in soil chemical and biological properties can significantly affect the yield of Eucalyptus plantation. However, the mechanism of soil chemical properties affecting wood volume mediated by biological factors is not clear. The purpose of this study was to identify which soil properties were affected by different fertilization intensities and to disentangle the dominant factors affecting Eucalyptus volume. After clear felling evergreen broad-leaved forest, a Eucalyptus plantation was established that was coppiced every 5 years and fertilized every year. Within this plantation, areas with different treatments were established. These treatments were a 5-year growth period (low); two times 5-year growth period (medium); and three times 5-year growth period (high). In each treatment area and in a nearby evergreen broad-leaved forest (EBLF Control), five sample plots per treatment were set up. Various biological and chemistry analyses (18 in total) were related to determining the most important path and index for optimizing Eucalyptus plantation. The analysis of variance of enzyme activity and microbial biomass showed that the soil biological characteristics decreased over 10 years of plantation, and the enzyme activity was close to the state of EBLF control in medium, while the microbial biomass failed to return to its original state during continuous planting. Redundancy analysis results show that there was a strong correlation in chemical indicators and biological characteristics. Partial least square structural equation model showed that total phosphorus, nitrate nitrogen, urease, catalase, and microbial biomass nitrogen and phosphorus were the most influential soil biochemical factors, and the indirect effect of chemical properties on volume was achieved by microorganisms through enzyme activity. Continuous planting and large-scale application of inorganic fertilizer would lead to a decrease in plantation yield and fertilizer utilization efficiency and would affect the microbial biomass and enzyme activity by destroying the stability of soil chemical properties.

In the review of the successful solar thermal electrochemical process (STEP) of acrylonitrile oxidation for the effective wastewater treatment, the process was actually driven by solar two fields - thermofield and electrofield, essentially activated and motivated for both thermochemistry and electrochemistry. In this paper, the synergistic system of solar three fields, induced by the primary photofield, and sub-thermofield and sub-electrofield, was designed and employed firstly for promoted the efficiency of the solar utilization and pollutant oxidation plus hydrogen production. With the correlative action, the three sub-chemical processes were induced by the solar three fields. The action actually conducted a three-field synergy of solar energy with a combination of the thermo-activation, photocatalysis and electrochemistry of the pollutant oxidation. Exemplified by acrylonitrile, the solar oxidation plus hydrogen production was theoretically and experimentally investigated by the single-field, coupled two-fields and coupled three-fields patterns. The results indicated that the coupled three-field pattern achieved high efficiencies in the solar utilization and oxidative reaction plus the hydrogen production, which was superior to ones of the single or two fields. The solar thermofield enables that the activated acrylonitrile was apt to be thermally decomposed, greatly in favor of the subsequent photo- and electrooxidation. The photocatalytic efficiency driven by the single photofield was reached at a rate of 31.01%. The electrolysis efficiency powered by single electrofield gained a rate of 24.56%. For the combination of the solar three-field pattern, the oxidation efficiencies run up to a rates of 32.74%, 38.06%, 55.01% and 76.01% during 60 min at the 25 °C, 40 °C, 60 °C, 75 °C, respectively. Especially, a joint of the coupled field realized the 6.38 times of the COD removal rate of acrylonitrile in comparison with the single field pattern. Due to the easy anodic oxidation of acrylonitrile and operation under the high temperature, the cathodic reduction of water was enhanced for the production of hydrogen in the electrolysis of the less potential plus an addition of photocatalysis. The experimental data and mechanistic analysis significantly revealed that the system achieved such a synergetic action. The full mineralization plus the hydrogen production was attributed to a coupling and matching integration of the solar three fields and subchemistries.

In this paper, secondary solar action to biomass, focused on the conceptualized intersection of solar energy and biomass, is presented to illustrate how “breaking” of biomass to biofuels plus hydrogen can be utilized for the adaptation of Solar Thermal Electrochemical Process (STEP) chemistry. This Solar Thermal Electrochemical Process (STEP) system was designed and employed for the synergetic solar energy and corresponding chemistry to provide an action of biomass for efficient solar and biomass utilization - production of biofuels plus hydrogen. The control and modulation of solar fields and sub-chemical reactions were adopted to achieve a high utilization of solar energy, high chemical conversion rate, and high selectivity of the biomass to achieve rich biofuels and abundant hydrogen. The Solar Thermal Electrochemical Process (STEP) temperature of the breakdown reaction was greatly lowered by using electrolysis, as compared with the conventional pyrolysis. Based on their structural complexity and thermal stability, cellulose and lignin are well-suited for the production of biofuel and hydrogen. Through the coupling of thermolysis and electrolysis, the Solar Thermal Electrochemical Process (STEP) hydrogen production from cellulose was 7.2 times higher under a current of 100 mA and 8.8 times higher at 400 mA compared with pyrolysis at 200 °C. The Solar Thermal Electrochemical Process (STEP) lignin conversions were significantly improved by reaching 87.22%, 21.78%, 57.72%, and 7.22% (340 °C, 400 mA), while the pyrolysis achieved only 52.39%, 19.48%, 25.81%, and 7.10% (340 °C, 0 mA), respectively, for the total rate, solid, liquid, and gas fractions. With electrochemical synergy to help, the Solar Thermal Electrochemical Process (STEP) process efficiently and selectively produced gas hydrocarbons, liquid biofuel, and hydrogen. The light hydrocarbons in the gas phase, such as methane, ethane, and n-pentane, became more abundant via thermo-electrolysis. The Solar Thermal Electrochemical Process (STEP) chemistry for converting biomass to biofuels and hydrogen was also elucidated in this paper. The simplified mechanism can best be described by a series of thermo/electro-induced free radical reactions. The system, built on solar energy and specific chemical reactions, features a perfect, green, sustainable, and recyclable operation to transform solar biomass to biofuels and hydrogen.

The solar thermal electrochemical process (STEP) degradation of nitrobenzene has been demonstrated as an alternative and sustainable way for wastewater treatment with both at high solar utilization and increased chemical efficiency enhanced by solar thermoelectrochemistry. This paper presents the first design and study of an integrated in situ thermoelectrochemical microreactor-analyzer, called in situ TEC-MRA, suitably fitted for an insight into pathways of solar-driven STEP oxidation of nitrobenzene. Based on the high sensitivity and resolution of nitrobenzene and intermediates for identification in the visible and UV range, the in situ TEC-MRA was explored and exploited for serving both as a reactor and analyzer, investigating the intermediates generated from the degradation, the critical time point in the progress and the energy consumption during electrolysis. The tests displayed that the device enables the response of real-time and fast chemical progress with high sensitivity and resolution, but without the interference from heat or mass transfer, thus displaying the thermoelectrochemistry of the STEP nitrobenzene oxidation and facilitating the control of energy input. A mechanism of STEP oxidation of nitrobenzene was schematized in detail. In the basis of the analysis of the in situ probing data, the oxidation and mechanism were clearly separated into three reaction sectors of decolorization, degradation, and mineralization. Furthermore, the advantage of the STEP was illustrated rather intuitively by a graphical interface for the high rate of STEP mineralization and the substantial savings in energy because of efficient solar utilization.

A fundamental principle in the culture of solar utilization has historically been to pursue the “Best Efficiency” and “Lowest Cost”, but currently the “Most Diversity” to opening new applications. To find innovative solutions for the realization of these goals, a new technology must meet the needs of the original photochemistry, as well as the electrochemical and thermochemical aspects. The STEP (Solar Thermal Electrochemical Process) was established as a comprehensive solar photo-thermo-electrochemical process to utilize solar energy for chemical reactions. To date, this has included STEP chemistries with high solar efficiency for generating hydrogen fuels, splitting carbon dioxide to generate fuels and graphite, separating iron metal from hematite ore, production of lime from limestone, production of bleach, wastewater treatment, organic synthesis and other useful chemistries. In this paper, we report a fundamental study of STEP chemistry in terms of the model, theory and practices of the existing applications. Fundamental insight was systematically demonstrated for STEP chemistry with high efficiency of solar utilization and chemical reaction. A mechanism for the overall construction and coupled combination of the STEP chemistry was developed and established in detail. The fundamentals of STEP chemistry include two aspects: improved solar utilization by enhancement of conversion efficiency, and adjustment of both the thermodynamics and kinetics of the reaction chemical reaction. The high overall solar efficiency can be achieved by the synergistically coupled combination of the solar utilization and chemical reaction to provide a total solution to the challenges of the energy and chemical industries.

Highly ordered TiO 2 nanotube arrays (TiO 2 NTs) were prepared through a facile two-step electrochemical anodization, subsequently, active iron ions were introduced into the TiO 2 NTs via a direct impregnation method. The XPS results showed that the iron elements existed in TiO 2 NTs in the form of Fe 3+ ions. Compared with the undoped TiO 2 NTs, the absorption edge of Fe 3+ /TiO 2 NTs showed an overt red shift and the photocurrent improved obviously, which indicated that Fe 3+ /TiO 2 had a much higher photocatalytic activity. The optimal doping content was tested to be 0.1 mol/L which could make the photocatalytic activity of TiO 2 NTs obviously improves under both visible and ultraviolent light. The prepared samples were adopted as photocatalyst to degrade nitrobenzene (NB). The reaction rate constants k s under UV light were in the order k one-stepTiO2NTs = 0.00338 k two-ste TiO NTs = 0.00455 k Fe3+/TiO NTs = 0.00736 which showed the superior photocatalysis activity of Fe 3+ /TiO 2 NTs. The final degradation products were probed to be CO 2 and H 2 O, which demonstrated that NB could be completely mineralized to harmless inorganic substance. The mechanism of NB degradation with Fe 3+ /TiO 2 was also discussed and the quenching experiments further confirm that OH, h + and O 2 − are active intermediates in the process of photocatalytic degradation.

This paper reports the adaptation of the Solar Thermal Electrochemical Process (STEP) for the treatment of formaldehyde in wastewater. The combination of thermochemistry and electrochemistry makes the STEP-formaldehyde treatment highly efficient with rapid kinetics. Indoor experimental results showed that the working potential is decreased and the oxidation rate is increased by raising the temperature of the reactor. Outdoor pilot tests demonstrated that the STEP-formaldehyde oxidation system can work smartly and efficiently without input of energy other than sunlight and without human intervention. The mechanism and kinetics were investigated by cyclic voltammetry (CV) and the in-time sampling and monitoring method. A robotic system is proposed for rapid treatment of formaldehyde using only solar energy.

The land preparation method of burning harvested residues considerably affects soil archaeal and bacterial communities. However, the changes in the archaeal and bacterial communities of Eucalyptus urophylla plantation and the driving factors of microbial community diversity are still unknown. This study explored the effects of E. urophylla replacement for native vegetation and the burning of harvested residues on the diversity of archaeal and bacterial communities. Soil samples were collected from the E. urophylla plantation with burnt (Burn) and retained (Retain) harvest residues after 5 years, and the native vegetation was selected as a control (CK). Results show that significant differences in soil organic matter, available phosphorus, available boron, soil bulk density, and moisture content were found among the three stands (p

Organic amendments can stimulate soil organic carbon (SOC) mineralization and soil aggregation simultaneously, which can improve C sequestration and soil fertility. However, the microbial mechanism governing C mineralization at the aggregate level remains uncertain. Here, we investigate how long-term organic amendments change SOC mineralization via affecting the microbial community composition and their co-occurrence pattern from micro-to macroaggregates. Four fertilization regimes from an 8-year field experiment were selected to study this mechanism, i.e., no fertilization (CK); inorganic NPK fertilizer (NPK); NPK + straw (NS); and NPK + straw and manure (NSM). Our results indicated that organic amendments significantly modified the C dynamics, bacterial and fungal community composition and network topological patterns in all aggregate sizes. Specifically, for microbial community composition, organic amendments increased the relative abundance of most Gram-negative bacteria and saprotrophic fungi. For microbial network relationships, organic amendments shifted keystone taxa from oligotrophs to copiotrophs in the bacterial network, and from Eurotiales to Sordariales in the fungal network, respectively. In addition, organic amendments alleviated competitive interactions coupled with keystone taxa in the bacterial network. These microbial changes were responsible for the increase of C mineralization in all aggregates, but the dominant microbial mechanisms varied with aggregate size. The alleviated competitive interactions coupled with keystone taxa of the bacterial network dominated the increases of C mineralization in macroaggregates, while the bacterial community composition did so in microaggregates. However, the fungal community composition only showed a significant impact on altering C mineralization in macroaggregates. Overall, our study provides a fundamental understanding of the microbial regulation of C dynamics at the aggregate level and highlights the importance of network topological patterns.

The Solar Thermal Electrochemical Process has been adapted to an organic decomposition reaction for application in wastewater treatment plus hydrogen production. The theory and process are proposed and exemplified by efficient decomposition of acrylonitrile (AN) as a model compound of environmental pollutants. The results demonstrate thermodynamically that a decrease in the decomposition energy/electrolysis potential can be achieved with an increase in reaction temperature by solar heating, which also leads to improved reaction kinetics to sustain high rates of decomposition at low electrochemical overpotential. It is demonstrated experimentally that the STEP decomposition process of organic pollutants plus hydrogen production is performed with high efficiency for the removal of acrylonitrile by 21.6% at 25 °C, 34.5% at 40 °C, and 56.3% at 75 °C using an applied current of 50 mA. The process provides lower potential and higher efficiency compared with the conventional electrochemical oxidation by balancing and controlling the thermal and electrochemical components. Based on the results of the CV, GC and experimental analysis, the pathways are proposed and explained for the thermo- and electrochemical decomposition of acrylonitrile using the solar STEP process. Due to the solar thermo- and electrochemical combination, this pathway is shifted from the indirect reaction of the conventional electrooxidation involving several intermediates to a direct pathway with rapid rate and high efficiency with synergetic production of hydrogen.

The clear-cut burning method for forest clearing has been widely used in Eucalyptus plantations in Southern China for successive planting generations. Harvest residues can provide a considerable nutritional supply for Eucalyptus plantations by affecting soil fertility qualities. Thus, harvest residue management is crucial. This study aims to investigate the effects of different management measures for harvest residues on the soil fertility of Eucalyptus urophylla × Eucalyptus grandis plantations and the changes in soil characteristics at different times and soil depths. We selected an evergreen broad-leaved forest (CK0) and a third-generation E. urophylla × E. grandis plantation (CK) as the control. The experimental plots were burned and retained the harvesting residue after CK harvesting. Soil samples were obtained one month, one year, and five years after burning (B1, B2 and B3, respectively) and retaining (R1, R2, and R3, respectively) the harvest residues. All measured soil properties were significantly affected by depth, stand, and interactions, except for the pH value. Discriminant analysis showed that the effects of different stands on the primary physicochemical properties of soil were higher than those on the microelement and biological characteristics. Varying stands had a significant influence on the primary physicochemical properties of soil across time. All stands were classified into four grades according to soil quality assessment values. The findings showed that CK0 obtained the highest score for grade I, followed by R2 (grade II); B1, R1, and R3 (grade III); and CK, B2, and B3, which had the lowest grade. Soil parameters were affected not only by soil depth but also by different management measures for harvest residues across time. In addition, although no significant difference was found in soil fertility quality between burning and retaining harvest residues in the short term (about a month), the soil fertility quality of a forest retaining harvest residues was significantly higher than that of a forest burning harvest residues in the long term.

In this paper, solar binary chemical depolymerization, that is Solar Thermal Electrochemical Process (STEP), was implemented for an effective breaking of lignin into small molecules and hydrogen. Compared with the conventional unitary chemical thermolysis, solar binary chemical depolymerization of lignin has high efficiencies of the liquefaction and gasification with the low coke, and accompanied by the abundant production of hydrogen. And the reaction temperature of the STEP process was greatly lowered by an intervention of the electrolysis. The results showed that the total conversion and liquefaction of the lignin yielded 87.22% and 57.72% under a constant current of 0.4 A at 340 °C. Further characterizations show that lignin has been successfully decomposed into small molecules with high added-value and hydrogen by a combination of the thermolysis and electrolysis. And the particle size of aggregates and the color degree in the lignin aqueous solution was obviously decreased after the STEP process.

In the paper, the isomorphous S O 4 2 − doped K 2 FeO 4 , aimed at the remediation of the discharge and stability of the super-iron battery, was first synthesized for doping and reforming the K 2 FeO 4 crystalline structure via a facile co-precipitation and mechanochemistry. Afterwards, the compared cathodes were assembled by the undoped and doped K 2 FeO 4 for an evaluation of the discharge and stability in the AAA super-iron battery system. The results show that the small amounts of K 2 SO 4 were doped into the K 2 FeO 4 in the calculated form of K 2 Fe 1−x S x O 4 by the isomorphous substitution. The doped K 2 FeO 4 cathodes/batteries exhibited an excellent discharge with a normal discharge profile. The cathodes doped by two techniques had significantly enhanced the discharge capacity of the super-iron battery with an increase of 10–30% compared to the undoped K 2 FeO 4 . Moreover, the stability of the K 2 FeO 4 cathodes was obviously remediated by the isomorphous S O 4 2 − doping. The shelf time of the doped K 2 FeO 4 cathodes was prolonged by an increase of about 10% in comparison of the undoped K 2 FeO 4 cathode. The desirable enhancements could be attributed to doping and reforming the similar building block and isomorphous S O 4 2 − into the Fe O 4 2 − tetrahedral and crystalline in the form of the isomorphous substitution and filling vacancies.

Environmental contextFull mineralisation of synthetic azo dyes in industrial wastewater is a tough job for traditional wastewater treatment technologies. There is an urgent need for the development of both sustainable and environmentally friendly technology capable of fully mineralising these azo compounds. We show that solar-driven advanced oxidation processes are capable of completely mineralising azo compounds with high utilisation of solar energy. AbstractMineralisation of synthetic azo dyes in industrial wastewater is an energy-intensive process in treatment technology. The Solar Thermal Electrochemical Process for advanced oxidation processes (STEP-AOPs) utilises solar energy and electricity for the activation and electrooxidation of organic pollutants to harmless, small and non-toxic molecules with no other energy consumption. Based on molecular structure and chemistry, the STEP-AOPs for the treatment of azo dyes in wastewater, as exemplified with a typical azo dye, methyl orange, is reported for the first time. Thermodynamic calculations of the temperature-dependent potentials of methyl orange demonstrate that Gibbs free energy decreased by 161kJmol–1 and the potential decreased by 0.019V with an increase of temperature from 20 to 80°C, which indicates that the drop in both energy and potential specifically fits the STEP-AOPs technique. Experimental results showed that the STEP-AOPs achieved a total organic carbon (TOC) removal of 95.6% for methyl orange. The TOC removal rate improved by 39.8% and the unit TOC electricity consumption decreased by 53.8% at 80°C compared with conventional methods (20°C). The mineralisation mechanism for methyl orange was a gradual shortening of the molecular chain through cleavage of the azo bond, breakdown of the benzene ring and formation of inorganic small molecules susceptible to be oxidised to non-toxic small molecules, and carbon dioxide via STEP-AOPs. The evidence shows that the STEP-AOPs is capable of mineralising azo compounds completely.