Boric Acid Cross-linked 3D Polyvinyl Alcohol Gel Beads by NaOH-Titration Method as a Suitable Biomass Immobilization Matrix

Abstract

Granule-base immobilization of biomass is a potential method for a decent quality granular sludge cultivation. In this study, 3D polyvinyl alcohol (PVA) gel beads were chemically cross-linked via a simple NaOH-titration method. The PVA gel beads' porous morphology was characterized using scanning electron microscope (SEM) and Brunauer-Emmette-Teller (BET), and their mechanical properties were evaluated by swelling rate and compressive stress tests. When cross-linking time was 10 min, high quality gel beads (P10) were synthesized, which demonstrated a homogeneous porous structure, good swelling rate, and high compressive strength. A mechanism for synthesis of the gel beads was proposed based on the results of Fourier transform infrared (FTIR) and X-ray diffractometer (XRD) analysis. Briefly, the intermolecular hydrogen bonds of PVA were firstly broken by NaOH to generate active bond of O-Na, which easily reacted with B(OH) 4 − to produce the PVA-boric acid gel beads. P10 showed excellent biocompatibility for anaerobic ammonia oxidation (anammox) biomass' immobilization. After incubation for three months, well granule-base immobilized sludge on P10 was developed in up-flow reactor. The sludge had high abundance of anammox biomass and was in balance with other functional bacteria. This work provides a simple method for the rapid preparation of 3D PVA gel beads and verifies their potential in granule-base immobilization of biomass.

A review on carboxylic acid cross‐linked polyvinyl alcohol: Properties and applications

“…A number of organic and inorganic agents were reported as PVA cross-linkers such as dialdehydes, [9][10][11][12][13] acid anhydrides, [14][15][16] diisocyanates, [17][18][19][20] transglutaminase, [21,22] polyurethane, [23,24] genipin, [25,26] boric acid, [27,28] epichlorohydrin, [29,30] mono/di/polycarboxylic acids, [31][32][33] alkoxysilane, [34,35] dimethyl carbonate, [36,37] epoxy compounds, [38] polyphenol, [39] carboxymethyl-chitosan, [40] and acrylic acid [41] . However, among them, several agents have different drawbacks such as some are cytotoxic, produce unpleasant odor, make PVA nonbiodegradable, or adversely affect the different properties of PVA.…”

Ice-Template Crosslinked PVA Aerogels Modified with Tannic Acid and Sodium Alginate

“…The –OH and C–O moieties from TA also interacted with calcium and borate ions since their bands were displaced and decreased [ 29 , 30 ]. Furthermore, the decreased intensity of the peaks at 1096 cm −1 indicated the reduction of PVA’s crystallinity as a result of the complexation with borate ions [ 31 ]. The band at 1409 cm −1 was attributed to B–O stretching vibration [ 32 ].…”

“…The band at 1409 cm −1 was attributed to B–O stretching vibration [ 32 ]. Since the solutions were adjusted with NaOH to pH 8.5, the samples’ alkalinity allowed the chemical connections between B(OH) −4 and –OH from PVA and TA, generating a dense network [ 31 ]. All the signals found in the PVA/TA/SA aerogels confirmed the presence of every precursor in the sample structure as well as the crosslinking effect.…”

Preparation of Poly(vinyl Alcohol) Microparticles for Freeze Protection of Sensitive Fruit Crops

“…The adsorption bands of C-H bending shifted from 1323 to 1330 cm −1 . This band is associated with the formation of alkoxide structures in PVA after alkali treatment [37]. A distinctive feature in the FTIR spectra of the microparticles was the appearance of a new band at 1647 cm −1 , which could be attributed to the O-H bending of bound water.…”