Search

Agent-based modeling (ABM) has been employed to understand and capture the complexity of the coupled human-nature processes in water resource systems. One of the challenges is to model human decisions in the coupled human and natural systems. Hydraulic fracturing water uses were distributed through a depot-based water allocation system in the Bakken region of western North Dakota, United States. In this study, a spatially explicit ABM was developed to simulate this unique water allocation system. In the ABM, institution theory was used to model the State’s regulatory policies and procedures, while evolutionary programming was employed to allow the water-depot owners (or agents) to select appropriate strategies when applying for water permits. Cognitive maps simulated the water-depot agents’ ability and willingness to compete for more water sales. All agents had their influence boundaries that restricted their competitive behavior toward their neighbors, but not for non-neighboring agents. The decision-making process was constructed and parameterized with both quantitative and qualitative information. The ABM was calibrated against real-world water-use data, and the calibration results showed that the spatial ABM performed well in simulating the total number of water depots as well as the locations and water uses of water depots at the county level. By linking institution theory, evolutionary programming, and cognitive maps, our study exhibited a new exploration of modeling the highly complex dynamics of the decision-making process involved in coupled human-nature water resource systems.

Novel composite adsorbents PPTA-AOx were synthesized by grafting polyacrylonitrile onto poly(p-phenylene terephthalamide) (PPTA) followed by converting the acrylonitrile into the amidoxime (AO) groups. Their structures were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, elemental analysis, transmission electron microscopy, etc. Scanning electron microscopy analysis and pore structure analysis manifested that PPTA-AOx adsorbents are all composed of nanoparticles aggregation. The as-synthesized PPTA-AOx adsorbents showed good adsorption capacity for Hg2+ with a maximum adsorption capacity of 2.50 mmol g−1. The pseudo-second-order model can reasonably describe the adsorption kinetics of the three adsorbents for Hg2+. Langmuir model provided better fit for the isothermal adsorption of Hg2+ on PPTA-AO1 and PPTA-AO2, while the Freundlich model was better for PPTA-AO3. The adsorption process might involve both chemisorption and physisorption. According to the calculated thermodynamic parameters, it can be concluded that the adsorption is an endothermic, spontaneous and entropy-driven process.

Two types of fibrous adsorbents, thiol- and amino- functionalized polysilsesquioxane coated poly(p-phenylenetherephthal amide) (PPTA) fibers (PPTA-PAPSQ and PPTA-PMPSQ), were prepared via the in situ condensations with aminopropyltriethoxysilane (APTES) and mercaptopropyltriethoxysilane (MPTES) on the surface of PPTA fibers, respectively. Their structures were characterized by FTIR, FE-SEM, XPS, XRD, TG, Elemental analysis, and pore structure analysis. The effect of the ratio of reactants on the structures of these two modified fibers was investigated. The results of nitrogen adsorption-desorption isotherms revealed that the polysilsesquioxane coating on the surface of PPTA-PMPSQ samples exhibited open meso- or macroporous features, while those on the surface of PPTA-PAPSQ samples formed dense gel structures. Moreover, Hg (II) was chosen as a representative to evaluate the adsorption properties of PPTA-PAPSQ and PPTA-PMPSQ samples. The results showed that the adsorption processes of Hg(II) followed well pseudo-second-order model onto the two series adsorbents. The Langmuir was the better-fit model to predict the experimental data. The theoretical saturation adsorption capacities of polysilsesquioxanes coated on the PPTA-PAPSQ and PPTA-PMPSQ adsorbents can reach 3.52–10.64 mmol g−1 and 7.43–10.22, mmol g−1, respectively. The result showed that PPTA-PAPSQ and PPTA-PMPSQ adsorbents can selectively adsorb Hg(II) from binary component metal ion systems.

A double reagents simultaneous functionalization (DRSF) was used to prepare porous polysilsesquioxane with NH2 and SH bifunctional groups (PAMPSQ) coated poly(p-phenylenetherephthal amide) (PPTA) fibers adsorbents (PPTA-AM), via in situ condensations with aminopropyltriethoxysilane (APTES) and mercaptopropyltriethoxysilane (MPTES). The PAMPSQ coated on the PPTA surface was in the form of nanoparticles and its morphology varied with the proportion of the reactants. The PAMPSQ exhibited loose open meso- or macroporous features. The functional groups utilization of PAMPSQ was much higher than those of polysilsesquioxane on the mono-functional adsorbents with thiol or amino groups. The selective adsorption of PPTA-AM adsorbents for Hg(II) in binary component metal ion systems indicated their potential application in environmental remediation. The adsorption mechanism of Hg(II) onto PPTA-AM was proposed.

In this work, a facile and effective approach was developed to enhance para-aramid fiber (AF). Poly-p-paraphenylene terephthalamide oligomer modified amino-functionalized multiwalled carbon nanotubes (PPTA-MWNTs-x) were prepared and deposited on the surface of AF. TEM and AFM analyses proved the successful grafting of PPTA oligomers onto the surface of MWNTs-NH2. The modified MWNTs showed better dispersion stability compared with that of MWNTs-NH2. PPTA-MWNTs-x deposited on the AF surface was characterized by SEM and XRD. SEM images showed a relatively homogeneous distribution of PPTA-MWNTs-x over the aramid fibers. XRD analysis showed the crystallographic index value of AF/PPTA-MWNTs-x increased significantly as compared to that of AF, suggesting a more regular and ordered crystalline structure. The tensile test and single fiber pullout test were conducted. The results confirmed that PPTA-MWNTs-x could greatly enhance the mechanical properties of AF and improve the interfacial properties of EP/AF and PP/AF composites.