Ultrafiltration Flux Research Articles

A novel Polyethersulfone/Chamomile (PES/Chm) mixed matrix membranes for wastewater treatment applications

In order to address the limitation of low flux in ultrafiltration (UF), a suitable additive is introduced into the base polymer to modify the membrane morphology, thereby enhancing flux rates. In this study, chamomile leaf nanoparticles (Chm NPs) were investigated as a novel green material for utilizing in UF membrane synthesizes. To enhance comprehension of the influence of Chm on the synthesis of PES UF membranes, a series of membranes were fabricated by including different quantities of Chm into the casting solution; (0, 0.5, 1.5, and 2 wt. %.). The synthesized membranes were fully characterized, through the porosity, pore size, hydrophilicity, membrane morphology, and UF efficiency. Manufactured PES/Chm membranes demonstrated significantly increased permeate water flux (PWF) (up to 498 kg/m2 h), which was four times that of the pristine PES membrane (116 kg/m2 h), besides that the bovine serum albumin (BSA) and Congo red dye (CR) rejection of PES/Chm membranes was still kept high. The enhanced PWF was mostly due to the more porous membrane structure and increased hydrophilicity. Meanwhile, the higher surface hydrophilicity of the PES/Chm membranes resulted in greater antifouling performance and the high flux recovery ratio (FRR) of 93 %. Based on the results of this research, the Chm may be used as a novel green additive with substantial application potential in the fabrication of UF membranes wastewater treatment.

A high flux ultrafiltration membrane with a multi-hydrophilic particle additive and controlled self-assembly of micellar particles

A tri-block-copolymer and dopamine hydrochloride were processed through micellization then mixed with high molecular weight PVP to modify PES membranes, yielding excellent membrane performance in terms of permeability and high pollutant rejection.

Amino-functionalized UiO-66-doped mixed matrix membranes with high permeation performance and fouling resistance

For the reduction of bovine serum proteins from wastewater, a novel mixed matrix membrane was prepared by functionalizing the substrate material polyaryletherketone (PAEK), followed by carboxyl groups (C-SPAEKS), and then adding amino-functionalized UiO-66-NH2 (Am-UiO-66-NH2). Amino-functionalization of UiO-66 was accomplished by melamine, followed by an amidation reaction to immobilize Am-UiO-66-NH2, which was immobilized on the surface of the membrane as well as in the pore channels, which enhanced the hydrophilicity of the membrane surface while increasing the negative potential of the membrane surface. This nanoparticle-loaded ultrafiltration membrane has good permeation performance, with a pure water flux of up to 482.3 L·m−2·h−1 for C-SPAEKS/Am-UiO-66-NH2 and a retention rate of up to 98.7% for bovine serum albumin (BSA)-contaminated solutions. Meanwhile, after several hydrophilic modifications, the flux recovery of BSA contaminants by this series of membranes increased from 56.2% to 80.55% of pure membranes. The results of ultrafiltration flux time tests performed at room temperature showed that the series of ultrafiltration membranes remained relatively stable over a test time of 300 min. Thus, the newly developed mixed matrix membrane showed potential for high efficiency and stability in wastewater treatment containing bovine serum proteins.

Exploring the impact of fouling on permeate flux and quality in ceramic ultrafiltration after treating poultry wastewater, and strategies for effective modelling and mitigation

Ultrafiltration was used to treat the poultry processing industry's wastewater to enhance the water quality, making it suitable for recycling within the process. With the application of a constant transmembrane pressure for the ultrafiltration process, the permeate flux decreased over time, while the permeate quality improved. Mathematical modelling of the flux data and permeate analysis revealed that cake layer formation was responsible for fouling but with some initial pore blocking. The study indicated that higher transmembrane pressure contributed to the formation and compression of the cake layer, resulting in improved permeate quality. Cleaning with water failed to eliminate fouling, but chemical cleaning with acid and base helped to restore the initial permeate flux. The process effectively removed almost all particles (>99 % reduction of turbidity), over 90 % of the chemical oxygen demand, and 40–80 % of total phosphorus. The efficiency of the phosphorus removal was lower for pre-treated wastewater as part of the phosphorus was already removed. Increasing the pressure from 1 to 3 bar significantly improved the removal of chemical oxygen demand, total phosphorus, and lipids by 10 % without negatively impacting the membrane-cleaning process.

Device Performance of a Tubular Membrane Dialyzer Incorporating Ultrafiltration Effects on the Dialysis Efficiency.

Membrane dialysis is one of the membrane contactors applied to wastewater treatment. The dialysis rate of a traditional dialyzer module is restricted because the solutes transport through the membrane only by diffusion, in which the mass-transfer driving force across the membrane is the concentration gradient between the retentate and dialysate phases. A two-dimensional mathematical model of the concentric tubular dialysis-and-ultrafiltration module was developed theoretically in this study. The simulated results show that the dialysis rate improvement was significantly improved through implementing the ultrafiltration effect by introducing a trans-membrane pressure during the membrane dialysis process. The velocity profiles of the retentate and dialysate phases in the dialysis-and-ultrafiltration system were derived and expressed in terms of the stream function, which was solved numerically by the Crank-Nicolson method. A maximum dialysis rate improvement of up to twice that of the pure dialysis system (Vw=0) was obtained by employing a dialysis system with an ultrafiltration rate of Vw=2 mL/min and a constant membrane sieving coefficient of θ=1. The influences of the concentric tubular radius, ultrafiltration fluxes and membrane sieve factor on the outlet retentate concentration and mass transfer rate are also illustrated.

Electro-controlled membrane coupling Fenton (E/M-Fenton) in treating nanofiltration concentrate: Removal performance and membrane fouling behavior

Fenton and membrane filtration are increasingly adopted as treatments to treat nanofiltration (NF) concentrates. However, dosing acid and alkali agents could pose environmental risks for the traditional Fenton. To address this challenge, the performance of traditional Fenton was investigated in NF concentrate treatment. The as-optimized conditions were Fe2+ 4 mM, H2O2 10 mM, and pH 3.5. The Fenton effectively degraded fluorescent materials, especially humic-like and fulvic-like substances. Based on these conditions, the traditional Fenton approach improved the specific ultrafiltration (UF) flux above 0.67. An increase in hydraulic shear among 0.4 ∼ 1.6 m/s and a decrease in filtration pressure between 30 ∼ 80 kPa benefited the UF reversible and irreversible fouling, respectively. The electro-controlled membrane coupling Fenton (E/M-Fenton) process was suggested by adding electrolysis, achieving the in situ production of H+ cations and OH− anions. Compared with the E/M-Fenton without internal recirculation, the porosity on the surface of the membrane was increased by 15.4% in the system with internal recirculation. Moreover, it averagely removed 66.5% of dissolved organic matter and 78.8% of UV absorbance at 254 nm, limiting the rigidity of the organic molecular structure and further improving the UF permeate. The E/M-Fenton slightly increased transmembrane pressure by 18%, performing stable UF fouling in a week. These results are essential to developing environmental-friendly strategies for Fenton to treat NF concentrate.

Synthesis of TiO2/MoSx/Ag nanocomposites via photodeposition for enhanced photocatalysis and membrane fouling mitigation

In this research, to improve photocatalytic organic pollutant removal, we synthesized amorphous MoSx (a-MoSx) and Ag on TiO2 via a two-step photodeposition method. The As-synthesized TiO2/a-MoSx/Ag (TMA) photocatalyst exhibited a highly enhanced photocatalytic degradation performance of methylene blue which showed 3.6 times higher reaction rate constant than that of TiO2 photocatalyst. Furthermore, TMA photocatalyst was applied to the ultrafiltration (UF) membrane to mitigate fouling of the membrane. To realize a stable immobilization of photocatalyst on the membrane surface, polydopamine (PDA), which is a biocompatible mussel-inspired adhesive material, was utilized to form an adhesive layer. After PDA coating, TMA photocatalyst was stably deposited on the UF membrane, resulting to increased hydrophilicity. Fouling was successfully mitigated by photocatalytic self-cleaning property of TMA deposited UF membrane and flux recovery ratio was improved by 28% under irradiation. Owing to the simple and easy approach of both photodeposition-based heterostructure photocatalyst synthesis and post-processing of photocatalyst coating on the membrane, we present that our strategy for membrane fouling mitigation is suitable for future membrane technology.

Fabrication of a Novel (PVDF/MWCNT/Polypyrrole) Antifouling High Flux Ultrafiltration Membrane for Crude Oil Wastewater Treatment

The present work deals with the fabrication of novel poly(vinylidene fluoride) (PVDF)/Multi-wall Carbon Nanotubes (MWCNT)/Polypyrrole (PPy) ultrafiltration membrane by phase inversion technique for the removal of crude oil from refinery wastewater. In situ polymerization of pyrrole with different concentrations of MWCNT ranging from 0.025 wt.% to 0.3 wt.% in PVDF prepared solutions. Measurement of permeability, porosity, contact angle, tensile strength, zeta potential, rejection studies and morphological characterization by scanning electron microscopy (SEM) were conducted. The results showed that membrane with (0.05% MWCNT) concentration had the highest permeability flux (850 LMH/bar), about 17 folds improvement of permeability compared to pristine PVDF membrane. Moreover, membrane rejection of crude oil reached about 99.9%. The excellent performance of this nanocomposite membrane suggests that novel PVDF modification with polypyrrole had a considerable effect on permeability with high potential for use in the treatment of oily wastewater in the refinery industry.

Ultrafiltration significantly increased the scaling potential of municipal secondary effluent on reverse osmosis membranes

Ultrafiltration (UF) was often used as pretreatment in front of reverse osmosis (RO) unit because of its high rejection efficiency of microbes and particles. However, in some cases UF pretreatment might show adverse effects on the RO membrane flux. In this study, the effects of UF pretreatment on secondary effluent water quality and its RO membrane fouling characteristics were explored. There was almost no change of water quality after UF with different molecular weight cut-off (MWCO) membranes (100, 30 and 10 kDa), including total dissolved solid (TDS), alkalinity, conductivity, ion concentrations, etc., while pH increased a little and dissolved organic carbon (DOC) declined by about 1 mg/L. On the contrary, the RO membrane flux of UF permeates presented clear decline in comparison to the secondary effluent. The membrane fouling velocity and steady-state flux of secondary effluent was 0.052 and 0.656, while fouling velocity increased (0.077, 0.071, 0.067) and steady-state flux decreased significantly (0.397, 0.416, 0.448) after 100, 30, 10 kDa UF membrane pretreatment. Scanning electron microscope (SEM) images showed many crystals on the fouled membrane surfaces, which turned out to be CaCO3 by Energy dispersive spectrometer (EDS) analysis and precipitation calculation. After the addition of UF retentates to UF permeates, scaling was prevented and crystals on the RO membrane almost disappeared, which implied the anti-scaling effect of the UF retentates with low concentration. According to anti-scaling performance experiments, the anti-scaling performance of 100 k, 30 k, 10 k retentates was 2.7%, 4.0% and 7.3%, respectively. Excitation emission matrix (EEM) and fourier transform infra-red (FTIR) results showed that these retentates retained by different MWCO membranes were similar and composed of protein-like substances and soluble microbial products. The effect of key minority components in RO system deserved further exploration.

Development of dynamic PVA/PAN membranes for pervaporation: Correlation between kinetics of gel layer formation, preparation conditions, and separation performance

Thin film composite (TFC) membranes possessing polyvinyl alcohol (PVA) selective layer and polyacrylonitrile membrane-support were developed via dynamic mode technique based on concentration polarization phenomenon. The effect of the molecular weight cut-off (MWCO) of membrane-support, concentration of PVA solution and filtration mode on the gel layer formation was studied via the analysis of kinetic curves of flux and PVA rejection in ultrafiltration. The effects of concentrations of PVA, glutaraldehyde (GA) and hydrochloric acid (HA), filtration time, and transmembrane pressure (TMP) on the structure and pervaporation (PV) performance of TFC membranes for ethanol dehydration were investigated. It was found that an increase in PVA concentration, duration of filtration and TMP results in an increase in the TFC membrane selective layer thickness. It was shown that pervaporation permeate flux decreased when TFC membranes were prepared using higher PVA concentration and longer time of PVA filtration. The pervaporative permeate flux through TFC membranes passed through the maximum at TMP of 3 bar, then became practically stable for membranes prepared at TMP in the range of 4-8 bar. It was attributed to the formation of microdefects of the selective layer due to the compaction-relaxation behavior of membrane support during selective layer formation at elevated pressures. It was also shown that the dependence of PV separation factor on the duration of PVA solution filtration passes through the maximum which is consistent with the time of the stable gel-layer formation calculated from the kinetic curves. The found optimal conditions for preparation of TFC dynamic membranes were following: dead-end ultrafiltration mode, the component concentrations in the solution — 1.0 wt.% PVA, 0.06 wt.% GA, 0.5 wt.% HA, using the simultaneous application technique (SimAT) with the filtration time — 10 min and TMP — 3 bar.

Integrated Membrane Process Coupled with Metal Sulfide Precipitation to Recover Zinc and Cyanide

In gold cyanidation plants, which include a zinc cementation process, there is a progressive increase in zinc content in the solution and a higher cyanide concentration in leaching tailings. Consequently, there are opportunities to: (i) recover zinc and cyanide from these solutions, (ii) generate a saleable ZnS by-product, and (iii) reduce cyanide consumption and cyanide concentration in leaching tailings. Previous studies have proposed the use of the SART (Sulfidization, Acidification, Recycling, and Thickening) process for this purpose; however, this process has disadvantages that must be addressed. This study presents the results of the experimental assessment of an alternative process, the SuCy process, which uses an integrated membrane process. The SuCy process is composed of a metal sulfide precipitation coupled with a membrane filtration stage, a membrane contactor step to recover and concentrate cyanide, and a final neutralization and ultrafiltration stage. The flux obtained for zinc sulfide separation was around 0.01 L/m2s, with cyanide recovery of 95% at 60 min, whereas flux for ultrafiltration was 0.22 L/m2s. A comparison with an experimental study of the SART process at laboratory scale showed that the SuCy process could obtain a higher zinc recovery and can reduce the solid–liquid separation equipment by around five times. Therefore, the SuCy process could be a promising alternative for zinc and cyanide recovery in gold cyanidation.

Role of biological granular activated carbon in contaminant removal and ultrafiltration membrane performance in a full-scale system

This study evaluated a long-term impact of biological activated carbon (BAC) filter that was employed in a full-scale drinking water treatment plant to enhance the removal of contaminants by the ultrafiltration (UF) process. The results showed that BAC enhanced UF performance by increasing the flux by 18.5% and extending the filtration run by 45%. The presence of BAC improved the removal of primary contaminants, including dissolved organic carbon (4–40%), UV 254 (10–57.7%), geosmin and 2-methylisoborneol (80%). BAC was also effective in decreasing the concentration of biopolymers, humic substances, (semi-)volatile organics, chlorite and halonitromethanes, thereby lowering contaminant load on the UF unit. The changes in primary water quality parameters in the combined process showed that the humic substances in dissolved organic nitrogen, low molecular weight substances in UV 254 , and fluorescence protein-like substances could be useful indicators for DBPs as these organic fractions had strong correlation with DBPs. Obvious spatio-temporal characteristics of GAC grain and microbial communities in BAC filter were observed with operation time and filter depth. The bacterial community in BAC filter was highly diverse and was less influenced by influent quality with an increase in filter depth, while the communities in UF cake layer correlated with organic removal in the UF system. • The BAC performance in a hybrid full-scale DWTP in combination with UF was studied. • BAC could increase the UF flux by 18.5% and extend the filtration run by 45%. • BAC removed 4–40% of DOC, 10–57.7% of UV 254 and 80% of 2- MIB in sand filtrate. • BAC was more effective in controlling N-DBPFP than C-DBPFP, in particular for HNMs. • The microbial communities in BAC filter exhibited temporal and spatial variability.

Antifouling efficiency and high-flux ultrafiltration membrane comprising sulfonated poly (ether sulfone) and TNTs-g-PSPA nanofiller

BackgroundClimate change, population growth, water pollution, and mismanagement of water resources all contribute to freshwater depletion. To cleanse dirty water, efficient and long-lasting technology is required. Membrane technologies are being developed to provide a cost- effective and efficient water treatment option to meet the ever-increasing demand for high quality- water. MethodsA facile method was performed to develop outstanding hydrophilicity, fouling resistance, high rejection rate and water flux ultrafiltration (UF) membrane. The membranes were made using a non-solvent induced phase separation (NIPS) approach by combination of sulfonated polyethersulfone (SPES) and Titania nanotubes (TNTs) modified with sulfopropyl methacrylate (TNTs-g-PSPA) as a nanofiller. The fouling resistance of the fabricated membranes was explored using various foulants, comprising humic acid (HA), sodium alginate (SA), bovine serum albumin (BSA), and natural organic matter (NOM) solution. Significant findingsThe results revealed that the membranes surface charge concentration, porosity, and textural properties were improved. The hybrid membrane's pure water flux containing 5 wt% TNTs-g-PSPA hybrid was 402 L m−2 h−1, around 2-fold that of the pristine membrane. The fashioned membrane with 4 wt% TNTs-g-PSPA removed greater than 98% of NOM, without a rejection rate loss.

Single Pass Tangential Flow Filtration (SPTFF) of monoclonal antibodies: Experimental studies and theoretical analysis

Single Pass Tangential Flow Filtration (SPTFF) enables continuous ultrafiltration and diafiltration for inline concentration and buffer exchange in downstream bioprocessing of monoclonal antibody (mAb) products. However, the high conversion in SPTFF modules leads to large variations in local flow rate, protein concentration, and transmembrane pressure drop, significantly complicating the design of effective SPTFF modules/processes. In this study, a recent concentration polarization model for the filtrate flux in protein ultrafiltration that accounts for protein-protein interactions has been extended to the analysis of SPTFF, specifically including the effects of the mAb and membrane properties as well as the long path-length. Model calculations are in good agreement with experimental data for the filtrate flux and pressure drop in two commercial SPTFF systems with very different module geometries. The model was then used to analyze the design of SPTFF processes for inline mAb concentration, providing additional insights into the underlying physical phenomena governing the performance and optimization of SPTFF modules for bioprocessing.

Robust ceramic nanofibrous membranes with ultra-high water flux and nanoparticle rejection for self-standing ultrafiltration

Ceramic electrospun nanofibrous membranes (ENMs) are ideal candidates for ultrafiltration applications in harsh environments. However, it has been a great challenge to fabricate ceramic ENMs with sufficient strengths to withstand the water pressure duo to their intrinsic brittleness. In this study, we report an ultra-strong Y3Al5O12-Al2O3 ENM employing graphene oxide (GO) as a sacrificing additive for the first time. The optimized membrane exhibits tensile strengths of 5.63 ± 0.31 MPa after sintering at 900 °C and 3.48 ± 0.44 MPa at 1000 °C. The high strength of the membrane ensures it to be used independently under a pressure up to 160 K Pa. An excellent nano-particle filtration performance is achieved with a high permeation flux of 5718–8494 L m−2 h−1 bar−1 and high rejection efficiencies above 99.75 % in both neutral and acidic water conditions. The work demonstrates a facile route for effective strengthening of ceramic ENMs with their great potential in harsh-environment self-standing ultrafiltration applications.

Hybrid Modeling for Simultaneous Prediction of Flux, Rejection Factor and Concentration in Two-Component Crossflow Ultrafiltration

Ultrafiltration is a powerful method used in virtually every pharmaceutical bioprocess. Depending on the process stage, the product-to-impurity ratio differs. The impact of impurities on the process depends on various factors. Solely mechanistic models are currently not sufficient to entirely describe these complex interactions. We have established two hybrid models for predicting the flux evolution, the protein rejection factor and two components’ concentration during crossflow ultrafiltration. The hybrid models were compared to the standard mechanistic modeling approach based on the stagnant film theory. The hybrid models accurately predicted the flux and concentration over a wide range of process parameters and product-to-impurity ratios based on a minimum set of training experiments. Incorporating both components into the modeling approach was essential to yielding precise results. The stagnant film model exhibited larger errors and no predictions regarding the impurity could be made, since it is based on the main product only. Further, the developed hybrid models exhibit excellent interpolation properties and enable both multi-step ahead flux predictions as well as time-resolved impurity forecasts, which is considered to be a critical quality attribute in many bioprocesses. Therefore, the developed hybrid models present the basis for next generation bioprocessing when implemented as soft sensors for real-time monitoring of processes.

Improved Desalination Performance of Polyvinylidene Fluoride Hollow Fiber Membranes by the Intermediate Role of Surfactants

AbstractPolymer hollow fiber membranes (HFMs) are the core or base membranes of various membrane processes (e.g., ultrafiltration and membrane distillation). Preparing polymer HFMs with higher water flux helps improve the efficiency of the membrane processes. Using pore‐forming additives is the commonly used and efficient method to improve the water flux. The current dilemma is that the conventional methods that increase the amounts or the molecular weight of the additives to improve the water flux usually lead to the decrease in membrane mechanical strength. Herein, different from the conventional research strategy, increasing the surfactant surface activity (SA) is first found to deeply promote the core of nonsolvent‐induced phase separation (NIPS) that of the mutual diffusion between water and dopes. As a result, this method distinctly improves the surface porosity (from 0.8% to 9.7%) and optimizes the pore size distribution of polyvinylidene fluoride (PVDF) HFMs. Benefit from these, the water flux of ultrafiltration (3.1‐fold increase, maximally) and direct contact membrane distillation (2.3‐fold increase, maximally) are increased greatly. Moreover, the mechanical strength is not negatively affected due to the additive amount of small molecule surfactants is constant and small (2.0 wt%).

Performance evaluation of filtration and ultrafiltration for municipal secondary effluent reuse

<p>This study aimed to evaluate the performance of microscreen drum filter and ultrafiltration (UF) as a ‎tertiary treatment to improve the secondary effluent quality. Additionally, hydraulic loading of ‎drum filter and membrane flux of UF were changed. On average, the use of drum filter and UF ‎reduced TSS to 50% and 100%, respectively. Furthermore, drum filter, on average, was capable of ‎reducing turbidity and COD to 36 and 20%, and UF decreased them to 76 and 39%, respectively. ‎Fecal coliform and total coliform were reduced to 74 and 76% in drum filter and 5.28 and 5.08 log ‎in UF, respectively. The results revealed that the combination of microscreen and UF is an effective ‎hybrid process for reducing physical parameters and coliforms in secondary effluent so that it can ‎meet the US Environmental Protection Agency standards for many uses, including unrestricted ‎urban uses and agricultural irrigation for food crops.‎</p>

Performance of hollow fiber ultrafiltration membrane in a full-scale drinking water treatment plant in China: A systematic evaluation during 7-year operation

Ultrafiltration (UF) was implemented as a process upgrade in a full-scale drinking water treatment plant (DWTP) with a scale of 100,000 m3·d−1, and the performance was systematically investigated over seven years of operation. The results showed that the UF system exhibited excellent rejection of particles and improved the removals of organics by 9.0–14.7%. The annual average UF flux decreased from 28.37 to 16.51 L·m−2·h−1, and it was necessary to employ various cleaning approaches at an increasing frequency for maintaining stable operation. Compared to the initial scenario, the total cost per m3 of water for the UF system after 7-year operation increased by 55%. The cost of membrane replacement, energy, waste water and chemicals played a decisive role on operating cost in the lifecycle of the UF system. The content of cations (i.e., Mg, Al, Si, Ca, Mn and Fe), biological metabolites and organic substances in the cake layer increased significantly during long-term UF filtration, which not only aggravated membrane fouling but also affected the organic composition of the drinking water. The excellent integrity of the UF membrane during the 7-year operation was sufficient to prevent breakthrough of the organic substances from metabolic activity of microorganisms and to ensure biological safety of the permeate.

Life cycle cost of dilution desalination in off-grid locations: A study of water reuse integrated with seawater desalination technology

Seawater reverse osmosis (SWRO) desalination is a proven technology for augmenting water supply in remote areas with limited access to fresh water resources. Lowering the energy consumption of SWRO is crucial in such areas where the source of energy is often reliant on transported liquid fuels. This study presents a life cycle cost model for two diluted desalination processes using water reuse to dilute seawater, and reduce energy consumption. The economic model details the life cycle capital and operational costs of i) a baseline SWRO desalination, ii) alternative osmotic dilution desalination in a forward osmosis (FO)–reverse osmosis (RO) hybrid system, and iii) a mixed dilution desalination process in an ultrafiltration (UF)–RO system. The results reveal a 4–5% lower total water cost associated with the two alternative processes compared to conventional SWRO. Sensitivity analysis revealed that the FO–RO system is an economically viable alternative to standalone RO if a water flux ≥6 L·m−2 h−1 and a recovery rate >25% can be achieved. The sensitivity analysis showed that diluted desalination with UF–RO was economically preferable to SWRO even when the water flux and recovery rate of UF meet only minimum thresholds (18 L·m−2 h−1 and 55%, respectively).