1. Introduction

As water scarcity becomes even more present in underdeveloped countries, developed states have to face a different challenge: water pollution from emerging contaminants [1]. Pollutants such as pharmaceutical residues come in a variety of forms and origins causing great issues [2, 3]. Many measures are established to reduce such contamination mostly in the form of water treatments and legislation [1]. However, great limitations are associated with the traditional techniques used in wastewater treatment plants. Most of them are due to either their cost or their low removal efficiency on emerging contaminants [4, 5]. For instance, degradation processes such as ozonation or chlorination were proven efficient for the degradation of organic molecules [6, 7]. However, these techniques have high operational costs and often cause dangerous degradation by-products that would follow the water flow and end up in rivers and lakes [8].

A specific technique distinguishes itself from the others; sorption. Such a treatment has the advantage of capturing contaminants with lower operational costs and without generating any dangerous by-products [5]. The most exploited sorbent is activated carbon (AC) which has high adsorption capacity and low specificity [5, 9]. Its efficiency comes from its high surface area on which contaminants can be adsorbed through interaction forces such as van der Waals [5]. It is often used for water purification through commercially available filters. Activated carbon can be made from various biological residues giving value to waste [9–11]. However, the synthesis of ACs necessitates the carbonization of the material itself and an activation step which can be costly and not environmentally friendly [5].

limited known uses, the electrospinning of lignin is not popular even if its

determined by using various desorption environments.

application are unprecedented.

DOI: http://dx.doi.org/10.5772/intechopen.88621

2.1 Chemicals and equipment

2. Methodology

PA, USA).

27

2.2 Electrospinning solution preparation

electrospinnability with a co-polymer is known [23–25]. Hence, the material and the

Sorption Capacities of a Lignin-Based Electrospun Nanofibrous Material for Pharmaceutical…

In this study, electrospun lignin nanofibres will be exploited for the adsorption of pharmaceutical residues in water. Precisely, fluoxetine and venlafaxine (antidepressant), carbamazepine (anticonvulsant) and ibuprofen (anti-inflammatory) will be tested for adsorption on developed nanofibres. The material's adsorption will be characterized by kinetic and isotherm studies. Its capacity to be reusable will also be

Alkali lignin (AL) low sulfur (28,000 Da, CAS 8064-05-1) and poly (vinyl alcohol) (PVA) 98–99% hydrolysis (31,000–50,000 Da, CAS 9002-89-5) were provided by Sigma-Aldrich (St-Louis, MO, USA). Sodium hydroxide pellets (NaOH) 98% (CAS 1310-73-2) and methanol HPLC grade (CAS-67-51-1) were provided by Alfa Aesar (Ward Hill, MA, USA). Hydrochloric acid (CAS 7647-01-0), acetonitrile HPLC grade (CAS 75-05-8), sodium citrate dihydrate (CAS 6132-04-3), sodium chloride (CAS 7647-14-5) and o-phosphoric acid HPLC grade 85% v/v (CAS 7664-38-2) were purchased from Fisher Scientific (Fair Lawn, NJ, USA). Fluoxetine hydrochloride (FLX) (CAS 56296-78-7), venlafaxine hydrochloride (VEN) (CAS 99300-78-4), carbamazepine (CAR) (CAS 298-46-4) and ibuprofen (IBU) (CAS 15687-27-1) were provided by Sigma-Aldrich (Oakville, ON, Canada). Citric acid anhydrous (CAS 77-92-9) was provided by Jungbunzlauer (Bale, Swiss). Commercial adsorbents used for comparison were Amberlyst® 15 (CAS 39389-20-3), Dowex® Marathon® C (CAS 69011-20-7), SiliaFlash® F60 40–60 μm particle size, fumed silica (CAS 112945-52-5) and Valfor® 100 sodium aluminosilicate zeolite respectively from Alfa Aesar (Ward Hill, MA, USA), Sigma-Aldrich (St-Louis, MO, USA), Silicycle (Quebec City, QC, Canada), and The PQ Corporation (Valley Forge,

The electrospinning setup was composed of a syringe pump (Kd scientific) and a power supply (Gamma High Voltage Research). Two laboratory ovens (Fisher Scientific Isotemp Oven and ThermoScientific HERATherm oven) were used for conservation and stabilization of the membranes. An orbital shaker (Lab Line model 3520) and an environmental orbital shaker incubator (Lab Line model 3528) were used for adsorption tests. Nanofibres were characterized using a Hitachi SUI510 scanning electron microscope (SEM). A Shimadzu Prominence I-series high performance liquid chromatograph (HPLC) coupled with a diode array detector (DAD) with a reverse phase column XB-C18, 100 Å, 150 3 mm, 2.6 μm particle size (Phenomenex, Kinetex®) was used to analyze contaminated water samples.

The electrospinning solutions were prepared as reported in Camire et al. [26]. Briefly, solution of AL and PVA 15% wt were prepared by dissolving AL in NaOH 1 M and PVA in water heated to 80°C for 60 min. After the dissolution, both solutions were mixed in a mass ratio of 1:1. This solution was stirred for an hour and settled at room temperature for another hour. The AL:PVA solution was then used directly for electrospinning or kept at 4°C in a refrigerator for a maximum of

Another option is the production of adsorbents from highly available natural polymers. Therefore, the product would be green, inexpensive and biocompatible. As many biosorbents are still being studied throughout the world, their potential is not fully exploited, and low attention is given to polymers such as lignin. Lignin, the second most abundant biopolymer after cellulose, is a naturally occurring polymer composing wood at 20–40% [12, 13]. Giving resistance and rigidity to the cell walls of plants, this biopolymer is water insoluble and resistant to organic solvents [12]. Lignin is also a highly variable biopolymer which is composed of its three main monomers (coniferyl alcohol, sinapyl alcohol and p-coumaryl alcohol) in a random pattern [13]. Its composition is further randomized by the addition of functional groups (mainly sulfate and carboxyl groups) during its extraction phase [13]. Even though it is variable, all lignins contain phenols, aliphatic alcohols and ethers [14]. Right now, lignin is mostly used to produce energy in the pulp and paper industry (where it is mainly extracted) and regenerate chemical reagents [15]. Although it is not its main use, lignin has already been used as an adsorbent for heavy metals or even dyes [16–19]. However, to our best knowledge, lignin has never been tested for pharmaceutical residues removal at trace levels. Therefore, the development of this lignin-based electrospun nanofibrous materials open up new opportunities for reducing inputs of pharmaceuticals into the environment.

To be able to achieve a satisfying adsorption capacity for trace contaminants and compete with AC, it is necessary to increase the surface area of the material. A simple way is the transformation of the polymer into nanofibres through electrospinning. This technique exploits the stretching of polymers exposed to a high voltage under defined experimental conditions [20, 21]. In electrospinning, a polymer is dissolved and introduced into a syringe (see Figure 1). Voltage is applied between the needle of the syringe and a collector plate. As a drop is formed at the tip of the needle, its surface tension will be disrupted by the electrical field and cause a Taylor cone and the formation of the fibres [22, 23]. Typically, fibres as thin as the nanometres scale are obtainable through this method [20, 24]. Because of its

Figure 1. Typical electrospinning setup.

Sorption Capacities of a Lignin-Based Electrospun Nanofibrous Material for Pharmaceutical… DOI: http://dx.doi.org/10.5772/intechopen.88621

limited known uses, the electrospinning of lignin is not popular even if its electrospinnability with a co-polymer is known [23–25]. Hence, the material and the application are unprecedented.

In this study, electrospun lignin nanofibres will be exploited for the adsorption of pharmaceutical residues in water. Precisely, fluoxetine and venlafaxine (antidepressant), carbamazepine (anticonvulsant) and ibuprofen (anti-inflammatory) will be tested for adsorption on developed nanofibres. The material's adsorption will be characterized by kinetic and isotherm studies. Its capacity to be reusable will also be determined by using various desorption environments.
