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With the rapid development of industry, water pollution caused by lead has caused great harm to human health. In this study, alginate is used as a base and blended with biochar to form calcium alginate hydrogel beads with high mechanical properties through ionic cross‐linking. Besides, the material (BC/MCAC) is prepared by the material (C‐γ‐Fe2O3) as a magnetizing agent and to remove lead. Then, a series of batch experiments and material characterizations are performed to evaluate the adsorption process of the material. The results show that the maximum adsorption capacity of BC/MCAC to Pb(II) is 211.6 mg g−1 at pH = 7. The adsorption process is well described by the Langmuir adsorption isotherm and pseudo‐second‐order kinetic model. This indicates that the lead adsorbed by BC/MCAC is a monolayer chemisorption that occurs on a uniform surface. After three regeneration cycles, BC/MCAC is found to retain 82.37% of the lead adsorption capacity and has good regeneration ability. Lead is removed by BC/MCAC mainly through the complexation of oxygen‐containing functional groups, electrostatic interaction, and ion exchange. BC/MCAC allows for more sustainable use of the wastes and is expected to be a new type of lead adsorbent for industrial wastewater. [ABSTRACT FROM AUTHOR]

The biggest bottleneck restricting the application of two-dimensional (2D) g-C3N4 material in water lubrication is the large-scale acquisition of g-C3N4 nanosheets with satisfactory water dispersibility. In this work, a gel-like g-C3N4 nanosheet hybrid with g-C3N4 nanosheet cores and organic shells was constructed from the bulk g-C3N4 by three procedures of Hummer's exfoliation, sulfonation, and acid–base neutralization. The hybrid in water exhibited nice water dispersibility and superior tribological performance. Adding 8 wt % of g-C3N4 nanosheet hybrid made the friction coefficient and wear volume of water reduce by 73.7 and 72.3%, respectively. Moreover, its load-carrying capacity under high load and durability under a long-term test were also impressive. The worn surface analyses reflected that a thick protective lubrication film (>150 nm) was distinctly formed on the surface lubricated by the hybrid aqueous dispersion. This film was actually a tribofilm composed of amorphous tribochemical reaction products (FexOy, FexSy, and Fex(SO4)y) embedded with FexOy and g-C3N4 nanocrystals, which not only remarkably reduced the friction and wear but also effectively restrained the oxidation and corrosion of the friction pair. Given the possibility of large-scale construction and the prominent tribological performance, the g-C3N4 nanosheet hybrid is a promising candidate to be developed as a particularly promising water-based additive. [ABSTRACT FROM AUTHOR]

The discharge of chromium-containing wastewater in industrial production causes resource loss and damage to the ecological environment. Currently, various phenolamine materials have been used to remove chromium, but their harsh adsorption conditions bring many difficulties. For example, ideal chromium removal is only achieved at low pH. In this study, we synthesized catechol/m-phenylenediamine nanospheres (CMN) and combined CMN with Fe(II) for Cr removal from aqueous solutions, and Fe(II) comes from FeSO4·7H2O. CMN was characterized and analyzed by field-emission scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), transmission electron microscopy (TEM), Fourier transformed infrared (FTIR), X-ray diffraction (XRD), X-ray photoelectron (XPS). The adsorption performance was studied through a series of adsorption experiments. When C0 = 900 mg/L and pH = 6, the maximum adsorption capacity obtained in the experiment was 977.1 mg/g. It maintains excellent adsorption properties in acidic, neutral and alkaline environments. The results of the adsorption mechanism showed that the ultra-high adsorption capacity of CMN and Fe(II) for Cr was the result of the synergistic effect of adsorption and reduction, including electrostatic attraction, reduction and coprecipitation. CMN is expected to be an ideal adsorbent for Cr removal in aqueous solution due to its low cost, high biocompatibility and high efficiency in Cr removal. [ABSTRACT FROM AUTHOR]

Acidic fracturing flowback fluid (AFFF) has the characteristics of low pH value, high chemical oxygen demand (COD), high corrosiveness and complex components. Surface discharge without treatment may contaminate the environment. However, wastewater treatment after centralized transportation has potential safety risks and requires high costs. In this study, we confirmed that calcium and magnesium could affect cross-linking property of fracturing fluid prepared by flowback fluid, and conducted a three-step process, two-stage filtration, chemical precipitation, and flocculation precipitation, on AFFF. After treatment, we made new hydraulic fracturing fluid using the treated acidic flowback fluid as base fluid and compared the quality of the new hydraulic fracturing fluid to the ones used freshwater as base fluid. The results showed when concentration of sodium carbonate, polyaluminium chloride (PAC), polyacrylamide (PAM) were 145, 1000, and 20 mg/L respectively, the treatment result was optimal. After treatment, the oil content of AFFF decreased from 7400 to 26.53 mg/L and suspended solids (SS) from 650 to 18.24 mg/L, and the removal rate of high-valence metal ions was more than 99%. The rheological properties and viscoelasticity of new fracturing fluid prepared by the treated AFFF were similar to the ones prepared by freshwater, which met the requirements of high temperature and shear resistance for ultra-deep wells. [ABSTRACT FROM AUTHOR]

In the study, a hydroxypropyl guar gum (HPG) gel was prepared using modified nano-TiO2 particles as a crosslinking agent. Firstly, nano-TiO2 particles were prepared using the sol–gel method. Nano-TiO2 particles were spherical and densely distributed; the effective particle size was 29.0 nm, and particle size distribution was uniform. Then, the modified nano-TiO2 particles were synthesized by modifying nano-TiO2 with polyhydroxy carboxylate. The microstructure of nano-TiO2 and modified nano-TiO2 crosslinked HPG gel were investigated. The layered distribution and crosslinked network of the modified nano-TiO2 gel were denser than that of nano-TiO2 crosslinked HPG gel. The modified nano-TiO2 crosslinked HPG gel shows stable viscoelasticity at 60 ℃. Compared with nano-TiO2 crosslinked HPG gel, it has better temperature resistance and shear resistance, and can adapt to formation fracturing at 140 ℃, indicating that this gel may have potential application in fracturing. [ABSTRACT FROM AUTHOR]

A chemical-modified biochar material (MGBC) derived from Brassica straw was synthesized using magnetic-gelatin as a modification reagent and employed to remove Cr(VI) from aqueous solution. MGBC before and after reacted with Cr(VI) was characterized by FT-IR, XRD, SEM-EDS, XPS, and VSM (Vibrating Sample Magnetometer). Characterization results indicated that the underlying mechanisms of remove Cr(VI) by MGBC were primarily relied on the chelation of functional groups and reduction-coupled surface precipitation. Additionally, the effect of pH, initial Cr(VI) concentration, adsorption time, ionic strength, and coexisting ions on adsorption capacity of MGBC were evaluated and optimized by batch adsorption experiments. All findings illustrated that the maximum adsorption capacity of MGBC for Cr(VI) was 434.85 mg/g obtained at pH = 1 and the adsorption process was highly dependent on pH, and well consistent with Freundlich model and Pseudo-second-order (PSO) model. Furthermore, approximately 72% of equilibrium adsorption capacity for Cr(VI) was still possessed by MGBC under a considerable degree of ionic strength or a given concentration of coexisting ions, which demonstrated that MGBC equipped with strong selective adsorption ability and anti-jamming capability in practical wastewater. All results herein manifested that MGBC equipped with favorable practicability and reusability, which could serve as a low-cost and high-efficiency adsorbent to remove Cr(VI) from complex water environment. [ABSTRACT FROM AUTHOR]

Polyethyleneimine (PEI) capped carbon nanoparticles (CNPs-PEI), gained by hydrothermal treatment of citric acid and PEI, were transformed into the polyelectrolyte capped CNPs (CNPs-PEI-NTf2) by HCl protonation process and anion exchange process between Cl− and bistrifluoromethanesulfonimide (NTf2−). The CNPs-PEI-NTf2 exhibited superb comparability with polyethylene glycol (PEG200). Their tribological behaviors as the lubricant additives of PEG200 were evaluated under the four-ball mode and steel/steel contact. Amazingly, adding particularly low amount (0.05 wt%) of CNPs-PEI-NTf2 made the friction coefficient and wear volume of PEG200 reduce by 66.1% and 86.6%, respectively. The surface analysis results of wear scars demonstrated that the CNPs-PEI-NTf2 as additives not only directly participated in the formation of mixed boundary lubrication films through the synergistic lubrication effect between the PEI-NTf2 groups and CNPs of CNPs-PEI-NTf2, but also should play the rolling, mending and polishing effects on the rubbing surfaces, and hence exhibited the outstanding friction-reducing and anti-wear functions. [ABSTRACT FROM AUTHOR]