Rapid uptake of pharmaceutical salbutamol from aqueous solutions with anionic cellulose nanofibrils: The importance of pH and colloidal stability in the interaction with ionizable pollutants

Abstract

Micropollutants escaping conventional wastewater treatment processes pose a threat to biota and the environment. Amongst micropollutants, small and ionizable organic compounds are particularly challenging, since their removal depends significantly on prevailing conditions.In this study, anionic cellulose nanofibrils (CNFs) were shown to perform as promising adsorbents for an ionizable pharmaceutical, salbutamol. The adsorbents were produced from wood cellulose through succinylation pretreatment in urea-LiCl deep eutectic solvent (DES), followed by a nanofibrillation procedure. The impact of pH, contact time, salbutamol 2 concentration, and adsorbent dose on salbutamol uptake were investigated in batch adsorption studies. Based on the results, the chemical modification of cellulose significantly enhanced the adsorption of salbutamol. The adsorption efficiency was mainly dependent on the charge and colloidal stability of the anionic nanofibril suspension rather than the charge of salbutamol, because the adsorption was considerably improved at pH>7 due to the deprotonation of the cellulose carboxyl groups. The experimental maximum adsorption capacity was 196 mg/g. This study highlights the potential of cellulose nanomaterial adsorbents and the importance of controlling the charge of the adsorbent material when developing solutions for ionizable micropollutant removal.

Efficient entrapment and separation of anionic pollutants from aqueous solutions by sequential combination of cellulose nanofibrils and halloysite nanotubes

“…Based on these results, it can be deduced that CNFs play a dual role in the studied process: they promote destabilization and aggregation of the colloidal clay mineral particles and they adsorb CAS. These findings are in line with previous results that cationic CNFs are efficient kaolin aggregators [59,60] and that functionalized CNFs work as efficient adsorbents for charged molecules [61]. The numbers on the photographs refer to the cellulose nanofibril dose (0-25 mg/g).…”

“…The impact of CNFs alone on CAS removal was verified by treating pure CAS solution with CNFs (15 mg/g, corresponding to 30 mg/L) at pH 6-8.5; the results showed consistent removal rates of 21-24% (q e 348-405 mg/g) (Figure S7). Previously, we used anionic CNFs as an adsorbent for pharmaceutical salbutamol and obtained ~12% removal with 25 mg/L CNFs (q e (exp) 196 mg/g) [61]. The higher removal efficiency observed in the current study compared with the previous one can be attributed to differences in the pollutant type and functional groups on CNFs, as well as their higher charge density.…”

“…There was no evident improvement in the CAS removal when the mixing time after CNFs addition was increased from 1 min to 24 h during the sequential, 2-step process (54-57%, q t 13-14 mg/g). The result was not surprising, because it is known that the adsorption of organic pollutants on CNFs is rapid [61]. Regarding the turbidity of the samples, an immediate floc formation and sedimentation was observed in the samples mixed for 1-60 min, and the supernatants were transparent (Figure S9).…”

Hydrophobic modification of nanocellulose and all-cellulose composite films using deep eutectic solvent as a reaction medium

“…Non-derivatized, pre-ground (Masuko super mass colloider MKCA6-2, Japan) dissolving pulp from softwood in aqueous solution (consistency of 1.66 wt.%) was used as a cellulose raw material for nanocellulose film production. Selkälä et al 2018 describe in detail the grinding procedure. TEAOH (35 wt.% in H 2 O) was from Sigma-Aldrich.…”

Surface Modification of Cured Inorganic Foams with Cationic Cellulose Nanocrystals and Their Use as Reactive Filter Media for Anionic Dye Removal

“… 33 − 37 The most prominent challenge related to the use of nanosized cellulose particles alone as adsorbents is the difficulty in separating the exhausted particles from the solution. 38 Therefore, cellulose nanoparticles are often used in combination with other materials, such as (nano)clay minerals, 39 metal particles, 40 and metal–organic frameworks (MOFs). 41 These hybrid materials can be removed after treatment, e.g.…”