Utilizing bentonite in composites such as concrete mixture is one of the practical approaches for adsorption of heavy metals. The mixture of bentonite and normal concrete is known as bentonite ...plastic concrete (BPC). This type of concrete is commonly utilized as the material of cutoff walls under earth dams with the aim of minimizing or preventing water seepage. Plastic concrete should possess high workability and consistency since it is poured into trenches by tremie pipe; this fact highlights the importance of predicting the slump of BPC. Different strength parameters of BPC such as compressive strength and elastic modulus can be predicted by utilizing prediction models. This information is exceedingly useful for modifying mixing design of BPC which results in reducing the cost and time of constructing a project. Consequently, it is vital to propose models that can predict the parameters of BPC with high precision. In this research, 158, 169, and 119 data records respectively for slump, compressive strength of cubic samples (f'c,cube), and elastic modulus (Ec) of BPC were collected from literature in order to propose prediction models. Three soft computing methods of artificial neural network (ANN), Multivariate adaptive regression splines (MARS), and M5 model tree (M5Tree) were utilized and compared in this paper. Then, parametric studies were conducted to study the effect of different variables such as silty clay addition, bentonite dosage, water content, and curing time on the outputs (i.e., slump, f'c,cube, and Ec). Results indicate that ANN models are more accurate than the other models for prediction of all three parameters. The water variable produces the greatest effect on the slump of BPC while the sand variable has the least influence. In addition, both for f'c,cube and Ec models, variables of cement and curing time have the maximum and minimum impact on the outputs, respectively.
•Three datasets of Slump, f'c,cube, and Ec of BPC were gathered from the literature.•Three methods of ANN, MARS, and M5Tree were compared.•ANN models were more precise than the other models.•The parametric studies were performed to investigate the behavior of ANN models.•The sensitivitsy analysis showed the influence of input parameters on models output.
This paper reports the preparation and characterization of a low-cost nano-TiO2 ultrafiltration membrane deposited on a bentonite support. The ultrafiltration layer was obtained by dip-coating ...process using nano-TiO2, followed by sintering at 750°C. Environmental Scanning Electron Microscope (ESEM) analysis of prepared ultrafiltration membrane showed that the deposited layer is homogeneous and shows a good adhesion on the support presenting a mean thickness of 4±0.2μm. The average pore diameter and water permeability of the obtained membrane are respectively 10±0.5nm and 16.08L/hm2bar. The membrane performance was evaluated by filtration of three different dyes: two anionic (Direct red 80 and Acid orange 74) and a cationic one (Methylene blue). Effect of feed pH and dyes concentration on membrane rejection was investigated at a pressure of 4bar. The experimental filtration results showed that rejection of Direct Red 80, Acid Orange 74 and Methylene Blue achieved maximum values of 98%, 85% and 94% respectively, depending on filtration conditions and each dye characteristics.
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•An effective low-cost flat UF membrane, by dip-coating of TiO2 deposited on a Bentonite MF support is proposed.•The hydrophilic TiO2 layer (thickness 4±0.2μm) shows good adhesion on flat bentonite support.•Resulting membrane presents a reasonable permeability (16.08L/hm2 bar) and good dye rejections (e.g., 98% for DR 80).•The membrane developed can be used as support to develop a NF membrane.
The preparation of NCC – bentonite nanocomposite using waste paper as the source of NCC was conducted in this study. The adsorption performance of the composite was tested for the removal of Pb(II) ...and Hg(II) from aqueous solution in single and binary systems. Langmuir and Freundlich adsorption isotherms were employed to correlate pure component adsorption isotherm. Langmuir equation can represent the experimental data better than Freundlich, the qm for lead is higher than mercury in both systems (single system qm = 0.44 mmol/g (Pb) and 0.23 mmol/g (Hg) for composite). All systems exhibit endothermic process, except for bentonite which shows the exothermic process. The modification of extended Langmuir model for a binary system with the inclusion of fractional loading and heat of adsorption was proposed in this study. The modified extended Langmuir model could represent the experimental data better than original extended Langmuir equation.
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•Waste paper was recycled to produce nanocrystalline cellulose.•The simple preparation of Nanocrystalline Cellulose – Bentonite composite was conducted.•Best adsorption performance in single and binary was achieved by using composite as adsorbent.•The modified extended Langmuir model can fit the binary system better than the original one.
Although metakaolin can enhance the hydration of cement, its pozzolanic reactions occur primarily at the early age with a high heat-release rate and low degree of reaction resulting in a reduction in ...the composite strength especially at high substitution levels. To address this challenge, a combination of metakaolin and sodium-bentonite is adopted as a partial replacement of cement. The influence of coupled substitutions of these two clays on hydration of Portland cement is investigated by characterizing hydration kinetics and products related to microstructural and physico-chemical parameters. The results indicate that the coexistence of sodium-bentonite and metakaolin enhances the cement hydration in terms of strength development, portlandite consumption and formation of supplementary calcium silicate hydrate (C-S-H) phases with elongated molecular chain lengths. Dissolution of metakaolin is increased in the presence of bentonite. It was found that the conversion of ettringite to monosulfate, the formation of strätlingite, and the length of aluminosilicate chains increase with increasing Al/Si ratio, which is related to the amount of dissolved metakaolin. A thermodynamic simulation is also presented to support these findings.
•HMCC immobilized Zn(II) mainly by forming Zn3(PO4)2·4H2O and humic acid-zinc complex.•Soil pH and bio-Zn were significantly related to the abundance of ARGs.•The potential host bacteria for ARGs ...mainly belonged to the phylum Actinobacteria.•HMCC addition increased the diversity of bacteria community but reduced the abundance of Actinobacteria.•HMCC could be used as an environmentally friendly amendment in manure-soil.
In this study, struvite-humic acid loaded biochar/bentonite composite (HMCC), a recovery product of humic acid, nitrogen and phosphorus from biogas slurry, was prepared and used for simultaneous control of Zn(II) and antibiotic resistance genes (ARGs) pollution in manure-soil. The adsorption performance and mechanism of Zn(II) on HMCC were first studied in aqueous solution. The adsorption data fitted well to the Freundlich isotherm model, and the primary mechanisms of Zn(II) absorbed by HMCC involved the formation of Zn3(PO4)2·4H2O and humic acid-metal complex. The changes of Zn(II) content, antibiotic resistance genes (ARGs) and bacterial communities during the remediation of Zn(II) contaminated manure-soil were analyzed simultaneously. With HMCC amendment, the content of bio-available Zn(II) (bio-Zn) efficiently reduced from 847.4 mg/g to 739.2 mg/g and the total relative abundance of ARGs accordingly decreased by 37.18%. RDA analysis indicated that soil pH and bio-Zn were the main contributors to the fluctuations of soil ARGs. Spearman correlation analysis revealed that the potential hosts for ARGs mainly belonged to the phylum Actinobacteria. In addition, HMCC addition increased the diversity of bacterial community but significantly reduced the abundance of an antibiotic resistant bacteria-Actinobacteria. It is the first study to demonstrate the feasibility of HMCC as an environmentally friendly amendment to immobilize Zn(II) and mitigate the dissemination of ARGs in manure-soil.
Bentonite was used as adsorbent, which was modified by aluminum cross-linking and tannin double modification (Al-Tan-Bent), and the adsorbent has excellent removal performance for ammonia nitrogen ...(NH4+-N) from low temperature wastewater. In the experiments, the effects of adsorbent dosage, pH, contact time, and coexisting ions were analyzed in detail. The kinetic models were fitted by experimental data, and the results showed that the adsorption process of ammonia nitrogen fitted well with the pseudo-second order kinetic model. Langmuir adsorption isotherm has higher correlation coefficient (R2 = 0.9992), the saturated adsorption capacity was 5.85 mg/g at low temperature. Electrostatic adsorption is the main mechanism for removing ammonia (NH4+), and the whole reaction was spontaneous and exothermic. Different preparation conditions of adsorbent were also analyzed: tannin concentration, temperature, pH and reaction time. The best preparation conditions for ammonia nitrogen removal were: 2 g/L of the modified concentration, pH = 7.5, modification time at 1 h and room temperature (25 °C) respectively. The adsorbents were characterized by Scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller (BET) surface area and Zeta potential. The presence of tannin on bentonite and the effects of different modified pH were confirmed. The sedimentation of the sample was significantly improved.
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•A new bentonite adsorbent for removing NH4+ from low-temperature wastewater was prepared.•More than 75% of ammonia nitrogen is removed under optimal conditions.•Electrostatic adsorption is the mechanism of ammonia removal by Al-Tan-Bent adsorbent.•Al-Tan-Bent adsorbent can be separated from water and recycled effectively.
A novel terpolymer of acrylamide (AM), 4-vinylpyridine (VP), and 2-acrylamide-2-methylpropanesulfonic acid (AMPS) was synthesized through free radical polymerization and characterized by proton ...nuclear magnetic resonance, Fourier transform infrared spectroscopy, elemental analysis, and static light scattering measurement. The monomer ratio was shown to be the predominant factor to the fluid-loss control performance of this polymer in drilling fluids. The terpolymer under optimal polymerization conditions (PAAV) was prepared, and the dipolymer of AM and AMPS (PAA) was synthesized as a contrast sample. In an American Petroleum Institute (API) filtration test of bentonite-based mud with 10% CaCl2 contamination after a 16 h aging at 150 °C, mud with 1% PAAV maintained an API filtrate volume (FLAPI) of 4.8 mL, whereas mud with 1% PAA reached a FLAPI of 96.0 mL. The fluid-loss control mechanism of PAAV was investigated through adsorption experiments, ζ potential measurements, and particle size distribution analysis. The results illustrate that the introduction of VP units into a polymer molecule greatly improves the temperature resistance performance of the polymer and enhances the interaction between the polymer and bentonite, which improves colloidal properties of bentonite particles, and these make PAAV a pronounced fluid-loss control agent in deep gypsum drilling operations.
Various water-based drilling fluids (WBDFs) are increasingly being used in oil and gas exploitation, for more environmentally acceptable and low-cost advantages than oil-based drilling fluids ...(OBDFs). However, WBDFs without an effective inhibitor easily facilitate shale swelling, hydration, and dispersion and even induce well instability, which is quite disadvantageous for well drilling. Thus, high-performance and environmentally friendly shale inhibitors are desperately needed for WBDFs, especially in deep and other challenging wells. Previously, gelatin was adopted as an environmentally friendly shale inhibitor in our group. However, the shale inhibition performance was limited at a high temperature. In this work, gelatin was further modified by 2,3-epoxypropyltrimethylammonium chloride (EPTAC, denoted as GT) to introduce quaternary amine functionalities and improve shale inhibition performance. The inhibitive property of GT was systematically evaluated through the linear swelling test, hot-rolling recovery test, and Na–bentonite (Na–BT) inhibition test. Results indicated that GT displayed better inhibition performance, especially at a high temperature, than pure gelatin and other common inhibitors. GT can be strongly adsorbed on the negatively charged clay surface via electrostatic attraction and hydrogen bonding, effectively decreasing the ζ potential of Na–BT particles and suppressing the double electrical layers. Meanwhile, GT effectively encapsulated and gathered the clay particles together, therefore preventing water ingress into clay and shale. GT showed great potential as a high-performance and environmentally friendly shale inhibitor for WBDFs.
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In this study, bentonite–Fe3O4–MnO2 composite was synthesized by combining bentonite with Fe3O4 and MnO2 through co-precipitation. Vibrating-sample magnetometry, scanning electron ...microscopy with energy-dispersive X-ray spectrometry, transmission electron microscopy, Brunauer–Emmett–Teller measurements, and X-ray powder diffraction techniques were used to characterize the composite. The composite consists of Fe3O4 nanoparticles orderly assembled on the surface of bentonite and an outer layer of MnO2 sheets. The composite’s particles possess a saturation magnetization of 13.4–30.5 emu/g and a high specific surface area (203.89 m2/g). The adsorption behaviors of the composite in Cd(II) removal were evaluated by batch equilibrium experiments. Kinetic and isothermal data fit well the pseudo-second-order and the Freundlich models, respectively. Adsorption reached equilibrium within 30 min, and the Freundlich capacity of the composite was 35.35 mg/g. The adsorption capacity of Cd(II) increased with increasing pH and was dependent on the ionic strength. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy showed the combination of surface hydroxyl groups of the composite and Cd(II) in the solution. The prepared composite can be easily recycled and reused by taking advantage of its magnetic properties. The results show that the designed composite is a promising absorbent for the treatment of Cd-contaminated water.
•PAAm/nB hydrogel nanocomposite was prepared via sonochemical method.•PAAm/nB efficiently scavenges Pb2+ and Cd2+ with Qm of 138.33 and 200.41 mg/g, respectively.•Pseudo-second order and Freundlich ...isotherm models appropriately describe the kinetics and equilibrium data, respectively.•Both intra-particle and liquid film models govern the adsorption mechanism.
Clay-hydrogel nanocomposites are suitable material for mitigating the pollution/environmental impact because of their high adsorption capacity. In this study, the synthesis of polyacrylamide/bentonite hydrogel nanocomposite was assisted by ultrasound through successful incorporation of nanobentonite as filler and cross-linker into polyacrylamide framework. The adsorbent was characterized by FTIR, XRD, BET, SEM-EDX, and TEM in order to observe structural changes and sorption interactions. The effect of adsorbent dose, contact time, initial metal ion concentration and pH on the sequestration of Pb2+ and Cd2+ was analyzed. The adsorbent removed more than 95% Pb2+ and Cd2+ within first 20 min, which corresponds to relatively high pseudo-first order rate constant, k1 (0.240 for Pb2+ and 0.253 1/min for Cd2+) and pseudo-second order rate constant, k2 (0.031 for Pb2+ and 0.033 g/mg/min for Cd2+). The isotherm and kinetics modeling data were best described by Freundlich isotherm over the entire concentration range and pseudo-second order rate equation, respectively. The thermodynamic studies implied spontaneous and endothermic nature of adsorption process. The maximum adsorption capacity (138.33 for Pb2+ and 200.41 mg/g for Cd2+) determined using Langmuir model along with a good regeneration potential depicts that polyacrylamide/bentonite hydrogel nanocomposite could be used effectively for Pb2+ and Cd2+ uptake from aqueous solution.
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