Intrinsic Dependence of Groundwater Cation Hydraulic and Concentration Features on Negatively Charged Thin Composite Nanofiltration Membrane Rejection and Permeation Behavior

Commercial nanofiltration membranes of different molecular weight cut-offs were tested on a pilot plant for the exploration of permeation nature of Ca, Mg, Mn, Fe, Na and ammonium ions. Correlation of transmembrane pressure and rejection quotient versus volumetric flux efficiency on nanofiltration membrane rejection and permeability behavior toward hydrated divalent and monovalent ions separation from the natural groundwater was observed. Membrane ion rejection affinity (MIRA) dimension was established as normalized TMP with regard to permeate solute moiety representing pressure value necessary for solute rejection change of 1%. Ion rejection coefficient (IRC) was introduced to evaluate the membrane rejection capability, and to indicate the prevailed nanofiltration partitioning mechanism near the membrane surface. Positive values of the IRC indicated satisfactory rejection efficiency of the membrane process and its negative values ensigned very low rejection affinity and high permeability of the membranes for the individual solutes. The TMP quotient and the efficiency of rejection for individual cations showed upward and downward trends along with flux utilization increase. Nanofiltration process was observed as an equilibrium. The higher the Gibbs free energy was, cation rejection was more exothermic and valuably enlarged. Low Gibbs free energy values circumferentially closer to endothermic zone indicated expressed ions permeation.

Improving membrane filtration performance through time series analysis

For ultrafiltration, and membrane filtration more generally, the quantitative determination of the modes of fouling remains a subject of great interest. Herein an integral method for determining the modes from a time series of volumetric flux $$J\left(t\right)$$ J t is given and illustrated with previously published filtration data of bergamot juice (Ruby-Figueroa et al (J Membr Sci 524:108-116, 2017)). The integral method of fouling analysis has the potential to become the cornerstone of a robust empirical process. In addition to determining, in a clear-cut manner, the point at which there is a switch from one mode to another, the robust methodology yields characteristic $$J\left(t\right)$$ J t equation for each mode that are an excellent fit to the data. The emphasis is upon the creation of a robust methodology which is best viewed as being a semi-empirical method that is indicative of the modes of fouling. For the example chosen, the initial 4 L/m2 generates some pore blocking after which the main mode of fouling is cake build-up. The variation of overall resistance with time is also informative and analysis of this series was used to check the result for the initial phase of fouling as determined from the time series of volumetric flux. A comparison against the ARIMA (Autoregressive integrated moving average) method, which has never been previously undertaken, is given herein. The integral method of fouling analysis was found to be superior, in part because of the quality of fit to the data and in part because it enables one to establish whether the initial fouling is different in character from the subsequent fouling. Having this information can improve membrane selection and overall membrane filtration performance.

Improving Membrane Filtration Performance Through Time Series Analysis

For ultrafiltration, and membrane filtration more generally, the quantitative determination of the modes of fouling remains a subject of great interest. Herein a clear method for determining the modes from a time series of volumetric flux J(t) is given and illustrated with previously published filtration data of bergamot juice (Journal of Membrane Science 524 (2017) 108-116). The emphasis is upon the robust methodology which is of general applicability and offers a straightforward approach to the modelling of flux decline. The method is best viewed as being an empirical method that determines the point at which there is a switch from one mode to another is determined in a clear-cut manner and it yields excellent equations for J(t). For the example chosen, the initial 4 L/m2 generates some pore blocking after which the main mode of fouling is cake build-up. The variation of overall resistance with time is also informative and analysis of this series was used to check the result for the initial phase of fouling as determined from the time series of volumetric flux. A strength of the integral approach is that it enables one to establish whether the initial fouling is different in character from the subsequent fouling. Having this information can improve membrane selection and overall membrane filtration performance.

Continuous biosorption of acid red 27 azo dye by Eichhornia crassipes leaves in a packed-bed column

In this work, the biosorption behavior of acid red 27 (AR27) dye using Eichhornia crassipes leaves (LECs) in a packed-bed column was investigated by varying relevant operational parameters and assessment of mathematical models. Results showed that the zero-charge point of LECs was 2.37 and that optima pH and volumetric flux of the influent solution for AR27 biosorption were 2.0 and $$56.5\ \hbox {L}/\hbox {m}^{2}\cdot \hbox {h}$$ 56.5 L / m 2 · h , respectively. The maximum specific and volumetric biosorption capacities were observed at influent AR27 concentrations and with LEC bed heights ranging between 50 and 400 mg/L and 2 and 8 cm, respectively. It was also found that if LEC bed height was increased and volumetric flux and AR27 concentration of the influent solution decreased, service and saturation time increased. Modeling results revealed that the Thomas, bed depth service time, Yoon–Nelson, dose-response, and logistic models accurately described the dynamic performance of the packed-bed column in terms of pH, AR27 concentration, and volumetric flux of influent AR27 solution, as well as that of LEC bed height. The findings revealed that LECs exhibited remarkable potential for the biosorption of AR27 from aqueous solutions in a packed-bed column and could potentially be useful for the treatment of AR27-laden wastewater.

A new method and apparatus for measuring in-situ air permeability of unsaturated soil

A new apparatus and an interpretation method simplified from existing solutions of spherical air flow in soil were developed to measure in-situ air permeability (ka) of unsaturated soil. By pumping air with a controlled volumetric flux (qv) into a spherical aeration bulb and measuring the corresponding pseudo-steady-state air gauge pressure (∆p0), ka was determined based on the slope of the qv-∆p0 relationship. The method was applied to measure ka in a full-scale landfill cover. The ka measurements were verified by finite-element modelling of air flow. The measurements show good agreement with the computed results. Sensitivity analyses reveal that using a smaller bulb radius (ro) would increase the measurement accuracy by minimising the boundary effects associated with atmospheric conditions and contrasting ka between neighboring soils. Yet, the use of a small bulb would result in more prominent effects of preferential flow and hence substantial overestimation of ka. For a small bulb size (r0=0.01 m), the measurement accuracy of ka could be within 15% (i.e., 2.4×10-13 to 6.3×10-13 m2) of the true values when the ratio of vertical-to-horizontal ka is between 0.4 to 1.

Motion of a spherical particle in a microbubble plume and the behavior of microbubbles around the particle

This study aims to investigate the motion of a solid spherical particle in a microbubble plume and the behavior of bubbles around the particle. Microbubbles (mean diameter 0.037 mm) released into a rectangular conduit by the electrolysis of water rise via buoyancy and form a bubble plume in the conduit. A solid spherical particle with a diameter of 10 mm and density of 1022 kg/m3 is placed on a mesh stretched across the cross-section near the bottom of the conduit, and microbubbles are then released from the cathode. Experiments are conducted with the bubble volumetric flux in the conduit j G at 0.05 and 0.09 mm/s. The particle repeatedly rises and falls when j G = 0.05 mm/s, and it rises almost vertically when j G = 0.09 mm/s. The absolute value of the vertical velocity of the particle is lower than that of the bubble. There is a belt-like region where the bubble velocity is extremely lower behind the particle. Such wake behind the particle clearly appears when the particle is falling, because the bubble velocity relative to the particle is higher.