3. Recent drifts in pH-responsive separation techniques

including wastewaters, radioactive waste streams, and separation of radionuclides, but it is not so favorable for the elimination of anions like boron, perchlorates, and nitrates. Adsorption processes would be upgraded by integrating with supplementary processes to obtain hybrid

Osmosis is a physical technique that has been widely examined by researchers in different branches of science and engineering. Early researchers considered osmosis through naturally occurring materials, and from the mid of the nineteenth century, extraordinary consideration has been given to osmosis through manufactured materials. Following the advance in reverse osmosis over the most recent couple of decades, particularly for forward osmosis applications, the interests in different engineering purposes of osmosis had been impelled. Osmosis, or as it is at present alluded to as forward osmosis, has modern applications in wastewater treatment, sustenance preparing, and seawater/saline water desalination. Other one of a kind of regions of forward osmosis look into incorporate pressure retarding osmosis for era of power from saline and unused water and implantable osmotic pumps for controlled medication discharge [6–8].

Recently, membrane technology has gained great attention as a powerful separation technique. Figure 1 shows the main categories of the membrane processes. They are categorized mainly based on the size of the contaminants they can exclude from the input stream. Nanofiltration (NF) is one of the fourth classes of pressure-driven membranes appeared after microfiltration (MF), ultrafiltration (UF), and reverse osmosis (RO). It was first developed in the late 1970s as a variant of reverse osmosis membrane [ROM] with reduced separation efficiency for smaller and fewer charged ions such as sodium and chloride. As the term, NF was not known in the 1970s, such that membrane was initially categorized as either loose/open RO, intermediate RO/UF, or tight UF membrane. The term NF appears to have been first used commercially by the Film-Tec Corporation (now the Dow Chemical Company) in the mid-1980s to describe a new line of membrane products having properties between UF and RO membranes. Owing to the uniqueness and meaningfulness of the word NF, other membrane scientists have begun using it [9–11]. Because of late advancements and advances in osmosis innovation, fascinating film operations, including membrane desalination (MD), pressure retarding osmosis (PRO), and reversed electrodialysis (RED), have developed. These operations are equipped for creating spotless and reasonable power from different waste streams, including brackish water and debilitated water, which generally are viewed as natural liabilities. PRO and RED require blending of a high salinity content (e.g., seawater or brackish water and wastewater, separately) with a low salt content to produce power. MD has demonstrated the possibility to produce freshwater and power as an independent process. Reconciliation of MD with PRO or RED upgrades the execution of these procedures and gives a perfect and practical course to create freshwater and

processes with higher removal efficiency [1–5].

2 Wastewater and Water Quality

2. Different categories of membrane processes

vitality [13–16].

Recently, membrane technology has gained great attention as a powerful separation technique due to prominent advantages over common processes such as high removal efficiency, low energy consumption, fast kinetic, small footprint, and ease of scale up. They are favored for full-scale applications due to normal operating conditions, high productivity, and low energy consumption. They can efficiently eliminate many contaminants including proteins, macromolecules, natural organic matters (NOMs), dyes, dissolved organic matter (DOM), boron, and compounds responsible for odor and color, from aqueous media. However, the recent achievements for pH-responsive membranes require an ion exchange separation in some cases. Figure 2 shows a combination between adsorption and membrane separation. The overall removal efficiency of the hybrid process would be enhanced [17–19]. Generally, three different procedures for hybridization of membrane systems with adsorption processes may be found:


Darmstadt, Germany, while Sigma-Aldrich tetraethyl orthosilicate (C2H5O)4Si 208.33 [g/mol],

Recent Drifts in pH-Sensitive Reverse Osmosis http://dx.doi.org/10.5772/intechopen.75897 5

Because of the immense difference between the traditional organic polymers and the corresponding inorganics in their natures and due to strong aggregation of the nanofillers, polymer-inorganic nanocomposite PAm-ZTS membranes cannot be prepared by common schemes such as melt blending and roller mixing. The most frequently secondhand synthesis techniques in the produc-

The sol-gel method, the former category secondhand preparation procedure, in which organic monomers, oligomers, or polymers and inorganic nanoparticle precursors are well balanced in solution. The inorganic pioneers were mixed together by gradual addition of tetraethyl orthosilicate, dissolved in equal volumes of bidistilled water and ethyl alcohol with vigorous stirring to zirconium oxychloride octahydrate and titanium tetrachloride solutions, previously dissolved in concentrated hydrochloric acid. The total components are instantly hydrolyzed in an appropriate quantity of water, following to condensation into well-dispersed nanoparticles in the polyacrylamide polymer skeleton with different mole fractions. The reactions' conditions are moderate; usually room temperature, an ordinary atmospheric pressure, and the concentrations of organic and inorganic components are easy to control over the solution. Additionally, the precursor ingredients, as organic and inorganic ingredients could be dispersed in nanometer level in the membranes, and thus the formed membranes are homogeneous. Other techniques as solution mixing and in situ polymeriza-

RO polymerized membranes are different in a couple of characteristics such as material, morphology, transport/separation mechanism, and applications [21–24]. Therefore, a large number of methodologies are required for their characterizations. They can be generally divided into three major tests, that is, methods used for chemical analysis, methods used for physical analysis, and filtration process for assessing membrane separation performance. Depending on the applicable utilization of RO membranes, their stability assessments against chlorination, organic solvent, thermal, and fouling can also be performed to examine

Table 1 describes some instrumental methods used in depicting RO membranes with respect to their chemical and physical characteristics, as well as their separation performances and stability. In a wide range, before conducting RO experiments, various techniques can be employed for their characterization in order to obtain a good knowledge of their parameters that are prominent for manufacturing a membrane with the right integration of water flux and solute rejection. For reverse osmosis pH-responsive membranes, zeta potential is well-thought-out as one of the significant parameters to determine the routes and mechanisms that the membranes

tion of nanocomposite membranes can be allocated as three categories [20].

5. Characterization of pH-responsive membranes

their sustainability under specific environments.

behave according to its chemical properties.

0.93 g/cm3 (20C), USA was used.

tion are used.

Figure 2. Membrane/adsorption hybrid process with adsorption pretreatment.

The current chapter deals with the adsorption/membrane integrated systems. As could be seen in Figure 2, some promising advantages of adsorption/membrane integrated systems could be obtained. They include:

