Shale gas extraction via horizontal drilling and hydraulic fracturing (HF) has enhanced gas production worldwide, which has altered global energy markets and reduced the prices of natural gas and ...oil. Water management has become the most challenging issue of HF, as it demands vast amounts of freshwater and generates high volumes of complex liquid wastes contaminated by diverse potentially toxic elements at variable rates. This critical review focuses on characterizing HF wastewater and establishing strategies to mitigate environmental impacts. High prioritization was given to the constituents with mean concentrations over 10 times greater than the maximum contamination level (MCL) guidelines for drinking water. A number of potentially harmful organic compounds in HF wastewaters were identified via the risk quotient approach to predict the associated toxicity for freshwater organisms in recipient surface waters. Currently, two options for HF wastewater treatment are preferred, i.e., disposal by deep well injection or on-site re-use as a fracturing fluid. Supplementary treatment will be enforced by increasingly rigorous regulations. Partial treatment and reuse remain the preferred method for managing HF wastewater where feasible. Otherwise, advanced technologies such as membrane separation/distillation, forward osmosis, mechanical vapor compression, electrocoagulation, advanced oxidation, and adsorption-biological treatment will be required to satisfy the sustainable requirements for reuse or surface discharge.
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•Shale oil and gas production via hydraulic fracturing poses risks to water quality and quantity.•High risk level is related with the management of hydraulic fracturing wastewater.•Wastewater quality data limitation is an obstacle for developing sustainable treatment strategies.•Integration of multiple technologies is required for wastewater reuse or discharge.
An in-depth study on the fixed-time event-triggered obstacle avoidance consensus control in heterogeneous USV-AUV systems with input delay and uncertain disturbances are conducted in this paper. When ...initial state of the system fails to achieve consensus, the desired heterogeneous USV-AUV formation can be achieved by fixed-time consensus control, within a fixed predetermined time, regardless of the initial states. Besides, an event-triggered communication strategy among the agents is introduced in the system, significantly reducing communication energy consumption. By employing the proposed control strategy, the Zeno behavior also can be avoided. Additionally, an obstacle avoidance control algorithm for the heterogeneous USV-AUV system based on improved artificial potential fields (IAPF) is designed, which helps in avoiding both static and dynamic obstacles. Compared to existing research, this algorithm reduces control input jitter, resulting in smoother obstacle avoidance paths. Through extensive simulation experiments and comparisons with other methods, effectiveness and superiority of the proposed algorithm is validated.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
This paper evaluates a novel sorbent for the removal of potentially toxic elements, inherent cations, and hetero-chloride from hydraulic fracturing wastewater (FWW). A series of iron-biochar (Fe-BC) ...composites with different Fe/BC impregnation mass ratios (0.5:1, 1:1, and 2:1) were prepared by mixing forestry wood waste-derived BC powder with an aqueous FeCl3 solution and subsequently pyrolyzing them at 1000 °C in a N2-purged tubular furnace. The porosity, surface morphology, crystalline structure, and interfacial chemical behavior of the Fe-BC composites were characterized, revealing that Fe chelated with CO bonds as COFe moieties on the BC surface, which were subsequently reduced to a CC bond and nanoscale zerovalent Fe (nZVI) during pyrolysis. The performance of the Fe-BC composites was evaluated for simultaneous removal of potentially toxic elements (Cu(II), Cr(VI), Zn(II), and As(V)), inherent cations (K, Na, Ca, Mg, Ba, and Sr), hetero-chloride (1,1,2-trichlorethane (1,1,2-TCA)), and total organic carbon (TOC) from high-salinity (233 g L−1 total dissolved solids (TDS)) model FWW. By elucidating the removal mechanisms of different contaminants, we demonstrated that Fe-BC (1:1) had an optimal reducing/charge-transfer reactivity owing to the homogenous distribution of nZVI with the highest Fe0/Fe2+ ratio. A lower Fe content in Fe-BC (0.5:1) resulted in a rapid exhaustion of Fe0, while a higher Fe content in Fe-BC (2:1) caused severe aggregation and oxidization of Fe0, contributing to its complexation/(co-)precipitation with Fe2+/Fe3+. All of the synthesized Fe-BC composites exhibited a high removal capacity for inherent cations (3.2–7.2 g g−1) in FWW through bridging with the CO bonds and cation-π interactions. Overall, this study illustrated the potential efficacy and mechanistic roles of Fe-BC composites for (pre-)treatment of high-salinity and complex FWW.
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•Fe-BCs were successfully synthesized via one-step pyrolysis of FeCl3-pretreated BC.•Fe to BC impregnation ratio determines their structural and surface chemical behavior.•Multiple contaminants simultaneously removed from high-salinity FWW.•Fe-BCs have multi-functionality for adsorption, reduction, and complexation.
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•Red seaweed food waste was used as a sustainable feedstock for LA production.•Microwave-assisted hydrothermal treatment facilitated fast red seaweed conversion.•High LA yield of ...16.3 wt% was obtained from Gracilaria lemaneiformis.•Algae hydrochar recovered can serve as a potential solid fuel.•Energy efficiency of 1.31 × 10−6 g LA/J and high carbon recovery of 73.3% were achieved.
In this study, red seaweed (Gracilaria lemaneiformis) food waste with high carbohydrate content was valorized into levulinic acid (LA) and algae hydrochar through microwave-assisted low-temperature hydrothermal treatment in dilute acid solution. Various parameters including treatment temperature (160–200 °C), reaction time (1–40 min), acid concentration (0–0.6 M), and biomass-to-liquid ratio (1%–10%, w/v) were examined. The energy efficiency and carbon recovery of the proposed process were investigated. Under the experimental conditions of 5% (w/v) biomass loading, 0.2 M H2SO4, 180 °C, and 20 min, the highest levulinic acid yield of 16.3 wt% was produced. The resulting hydrochar showed approximately 45–55% energy yield and higher heating values of 19–25 MJ kg−1. The energy efficiency of the present study (1.31 × 10−6 g LA/J) was comparable to those of the conventional hydrothermal treatment of lignocellulosic biomass, while the reaction time (20 min) was much shorter with a high carbon recovery (73.3%).
An end-to-end sea fog removal network using multiple scattering model was proposed. In this network, the atmospheric multiple scattering model was re-formulated and used for sea fog removal. Compared ...with the atmospheric single scattering model, the atmospheric multiple scattering model could more comprehensively consider the effect of multiple scattering, which was important to the dense fog scenes, such as in ocean scene. Therefore, we used the atmospheric multiple scattering model to avoid image blurring. The model can directly generate the dehazing results, and unify the three parameters of the transmission map, the atmospheric light and the blur kernel into one formula. The latest smooth dilation and sub-pixel techniques were used in the network model. The latest techniques can avoid the gridding artifacts and the halo artifacts, the multi-scale sub-network was used to consider the features of multi-scale. In addition, multiple loss functions were used in end-to-end network. In the experimental results, the model was superior to the state-of-the-art models in terms of quantitatively and qualitatively.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
This study investigated the simultaneous desorption of trace metal elements and polychlorinated biphenyl (PCB) from mixed contaminated soil with a novel combination of biosurfactant saponin and ...biodegradable chelant S,S-ethylenediaminedisuccinic acid (EDDS). Results showed significant promotion and synergy on Pb, Cu and PCB desorption with the mixed solution of saponin and EDDS. The maximal desorption of Pb, Cu and PCB were achieved 99.8%, 85.7% and 45.7%, respectively, by addition of 10 mM EDDS and 3000 mg L−1 saponin. The marked interaction between EDDS and saponin contributed to the synergy performance. The sorption of EDDS and saponin on soil was inhibited by each other. EDDS could enhance the complexation of metals with the saponin micelles and the solubilization capabilities of saponin micelles for PCB. Our study suggests the combination of saponin and EDDS would be a promising alternative for remediation of co-contaminated soils caused by hydrophobic organic compounds (HOCs) and metals.
► A novel combination of biosurfactant saponin and EDDS was used to simultaneously remove mixed contaminations from soil. ► Significant synergy on Pb, Cu and PCB desorption were achieved with EDDS/saponin. ► The marked interaction between EDDS and saponin contributed to the synergy performance.
Significant synergistic effect on Pb, Cu and PCB desorption were achieved with the mixed solution of saponin and EDDS.
This paper studies the time-varying formation reconfiguration control for multiple underactuated autonomous underwater vehicles (AUVs) with an Euler–Lagrange-like model. The goal is to control a ...fleet of AUVs to achieve any desired formation shape using a distance-based graph rigidity and affine transformation (GR-AT) algorithm. Firstly, the distance-based graph rigidity with backstepping technology is utilized to solve the formation controlproblem, and we acquire the initial nominal formation. In the sequel, we transform the nominal formation into any desired formation shape using the properties of the affine transformation (including translation, scaling, rotation, shearing, or a combination of them). Even the geometric shapes formed can be constantly changed. The Lyapunov stability theory can ensure the uniform ultimate boundedness of whole distance errors. Finally, several simulation examples with formation reconfiguration are given to validate the efficacy of the designed control methods. Moreover, some experimental results are presented to confirm the validity and applicability of the scheme with four real bionic robot fish.
•The underactuated AUVs are considered in this paper.•Graph rigidity and backstepping techniques are employed to achieve formation control.•Affine transformation technique is used to realize formation reconfiguration.•The Lyapunov based stability analysis shows that the proposed controller is stable.•Experimental results demonstrate the effectiveness of the proposed scheme.
This study described the adsorption of chloramphenicol (CAP) in wastewater on the renewable bioresource of bamboo charcoal (BC). Results showed that CAP adsorption on BC (Ln
q
e
=
1.272 Ln
C
e
+
...1.971) and H
2SO
4 modified BC (Ln
q
e
=
1.851 Ln
C
e
+
0.659) were very slight, and on NaOH modified BC was significantly increased (Ln
q
e
=
0.344 Ln
C
e
+
6.490). The adsorbents were characterized by N
2 adsorption–desorption, X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). It is revealed that BC and modified BC had very small surface areas of less than 1
m
2
g
−1, H
2SO
4 treatment led to minimal variation in surface functional groups, and NaOH treatment increased the percentage of surface graphitic carbon and other oxygen-containing groups. The increased adsorption of CAP on NaOH modified BC was mainly ascribed to the enhancement of the π–π interaction between the adsorbent and adsorbate.
In water scenes, where hazy images are subject to multiple scattering and where ideal data sets are difficult to collect, many dehazing methods are not as effective as they could be. Therefore, an ...unsupervised water scene dehazing network using atmospheric multiple scattering model is proposed. Unlike previous image dehazing methods, our method uses the unsupervised neural network and the atmospheric multiple scattering model and solves the problem of difficult acquisition of ideal datasets and the effect of multiple scattering on the image. In our method, in order to embed the atmospheric multiple scattering model into the unsupervised dehazing network, the unsupervised dehazing network uses four branches to estimate the scene radiation layer, transmission map layer, blur kernel layer and atmospheric light layer, the hazy image is then synthesized from the four output layers, minimizing the input hazy image and the output hazy image, where the output scene radiation layer is the final dehazing image. In addition, we constructed unsupervised loss functions which applicable to image dehazing by prior knowledge, i.e., color attenuation energy loss and dark channel loss. The method has a wide range of applications, with haze being thick and variable in marine, river and lake scenes, the method can be used to assist ship vision for target detection or forward road recognition in hazy conditions. Through extensive experiments on synthetic and real-world images, the proposed method is able to recover the details, structure and texture of the water image better than five advanced dehazing methods.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
In this paper, the fixed-time event-triggered obstacle avoidance consensus control for a multi-AUV time-varying formation system in a 3D environment is presented by using an improved artificial ...potential field and leader-follower strategy (IAPF-LF). Firstly, the proposed fixed-time control can achieve the desired multi-AUV formation within a fixed settling time in any initial system state. Secondly, an event-triggered communication strategy is developed to govern the communication among AUVs, and the communication energy consumption can be decremented. The time-varying formation obstacle avoidance control algorithm based on IAPF-LF is designed to avoid static and dynamic obstacles, the desired formation is maintained in the presence of external disturbances, and there is no Zeno behavior under the fixed-time event-triggered consensus control strategy. The stability of the system is proved by the Lyapunov function and inequality scaling. Finally, simulation examples and water pool experiments are reported to verify the performance of the proposed theoretical algorithms.
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