The repository contains data presented in paper "Pectin recovery from apple pomace by forward osmosis – Assisted technology" (https://doi.org/10.1016/j.memsci.2024.122956.
Aim of study:
This study aims to verify the feasibility of concentrating real apple pomace (RPE) extracts by FO. The study aims to reveal the effect of the FS pretreatment procedure on the concentration effectiveness, which is pivotal for FO implementation on an industrial scale. Moreover, a comprehensive fouling analysis is provided to evaluate its negative impact on the process. The osmotic backwashing is considered for restoring the separation properties of the FO membrane after the consecutive concentration processes. To enhance the technological capacity of the presented research, a techno-economic evaluation is also presented.
Methods:
Pristine and fouled membrane samples were air-dried for 48 h before microscopic examination. Elemental composition analysis was conducted on the membrane surface by energy-dispersive X-ray spectroscope (EDS) using a Thermo Scientific NSS spectral imaging system equipped with a BSE detector. Prior to scanning electron microscopy (SEM) analysis, membrane samples were carbon-coated using a Cressington Carbon Coater 108 carbon/A. The Hitachi S-3400 N SEM microscope, equipped with a SE detector, was used for surface and cross-section imagining. A membrane sample was prepared for cross-section analysis by liquid nitrogen freezing then cutting with a scalpel perpendicularly to the filtration surface.
The membrane surface topography was characterised using an atomic force microscope (NX10, Park Systems, South Korea) in tapping mode. All-In-One D AFM cantilevers (Budget Sensors, Bulgaria) with a nominal force constant of 40 N∙m-1 were used. The scanning speed ranged from 0.3 to 0.5 Hz and scanning size was from 2 μm × 2 μm to 15 μm × 15 μm. The scanning size of 10 μm × 10 μm showed consistent data and was selected for reporting. Data from AFM analysis were processed using the Gwyddion software.
- surface free energy data, summarized:
Contact angles (CA) on the pristine, fouled, and osmotically backwashed membrane, measured via water and diiodomethane, aimed at calculating the surface free energy (SFE). The sessile drop methodology was implemented utilizing the Theta Lite optical tensiometer (Biolin Scientific) and processed in the One Attension software. Samples of CTA FO membranes were air-dried for 48 h before measurement and fastened to the coverslip. The ultrapure water (18 MΩ∙cm, TOC 1–3 ppb, pH 6.25) from the PureLab Classic UV system (ELGA) acted as a polar measuring liquid and diiodomethane (Sigma Aldrich, ≥99%) as a nonpolar. The digital camera captured the shape of droplets (2 μL) placed on the surface of the membrane via an automatic dispenser. For each measuring liquid released on every sample, at least ten measurements were repeated, averaged, and used to calculate SFE according to the Owens, Wendt, Rabel and Kaelble (OWRK) theory.
- flux, water recovery and time - processes data:
Asymmetric CTA membrane (FTSH2O) was obtained from Fluid Technology Solutions (USA) and is characterised in Table SM1. Dewatering experiments were conducted in FO mode (active layer facing the FS) using a two-chamber plate-and-frame membrane module. The membrane effective area was 32 cm2. The FS and DS flows counter-currently at 30 L·h-1 (equivalent to a cross-flow velocity of ca. 57.4 cm·s-1). All FO experiments were conducted for 360 min. 3 M NaCl was used as the DS, corresponding to an osmotic pressure of 124.2 bars. FS in this study includes: apple pomace extract containing 2 g·L-1 of pectin, subjected to one-step pretreatment (sieve filtration) denoted as RPE I, apple pomace extract containing 2 g·L-1 of pectin, subjected to two-step pretreatment (sieve filtration and centrifugation) denoted as RPE II, and single-component model solution of 2 g·L-1 high-methoxyl pectin solution (referred to as the model pectin solution).
Dry apple pomace and extraction enzyme were from our industrial partner (Tłocznia Jabłuszko Jarosław Ozdoba, Poland). Dry apple pomace was mixed with deionized water in a weight ratio of 1:15. Then, 15 mL of the Celluclast 1.5 L enzyme was added to each litre of the mixture. The extraction process was carried out for 18 h at 25°C with continuous stirring. After pectin extraction, solid residue was separated from the aqueous solution by mesh sieving (one-step pretreatment) or a combination of mesh sieving and centrifugation (4100 rpm for 10 min) (two-step pretreatment).
The osmotic pressure to calculate reverse salt flux was determined based on osmolality measurements using an osmometer OS 3000 (Marcel, Poland). For every test, a sample of 1 mL was collected and diluted 10 times. Afterward, 0.1 mL of the sample was placed in an Eppendorf test tube to measure osmolality.
Conclusions:
This study demonstrates the utility of FO for concentrating the real apple pomace extract as an alternative or support to widely used evaporation techniques. The FO process, when integrated into the processing chain for pectin recovery, offers efficient and cost-effective enrichment of pectin in apple pomace extract for subsequent recovery. Results in this study show notable membrane fouling with up to 70% flux decline when FO is used to concentrate pectin. The nature and severity of fouling were influenced by the type of the FS used. However, fouling was completely reversible by osmotic backwashing as demonstrated by multiple filtration cycles. A comprehensive techno-economic assessment shows significant reduction in capital investment requirement and operating cost when FO is used to enhance pectin recovery. The payback period can be shortened from over 5 to 2 yr when applying FO to concentrate pectin by 5 times. Further optimization of the osmotic concentration process and DS regeneration is recommended to enhance the application potential of FO in the future.
