Abstract
The influence of star-shaped (PAA-SS) and linear polyacrylic acid (PAA) with different molecular weights (high—PAA-HMW and low—PAA-LMW) on the structure of the adsorption layer, adsorption amount, electrokinetic and stabilizing properties of the PAA/CTAB/nanoclay suspensions was studied. The properties of the systems containing one of these polymers, the cationic surfactant—hexadecyltrimethylammonium bromide (CTAB) and the surface-modified nanoclay (N-SM) were analyzed using the following techniques: BET, CHN, FT-IR, ED-XRF, XRD, HRTEM, UV-Vis, tensiometry and zeta potential measurements. It was proved that PAA could be used as an effective stabilizer of N-SM. Moreover, the addition of CTAB caused a significant increase in the stability of the systems but decreased the adsorption of PAA on the N-SM surface and changed the structure of the adsorption layers. The largest stability was observed in the PAA-HMW/CTAB system. The PAA polymers and PAA/CTAB complexes adsorbed, especially on the clay surface, influenced the primary distribution of the layered sheets but kept the same basal d-spacing. The adsorption of PAA and the PAA/CTAB complexes took place mainly at the plate edges and on the contact space between the sheets. The obtained results will be used for the preparation of the PAA/CTAB/nanoclay composite for water purification.
Highlights
UV-Vis spectrophotometry allows for an estimation of the amount of polyacrylic acid (PAA) or PAA/cationic surfactant—hexadecyltrimethylammonium bromide (CTAB)
Sample, the increase in basal spacing d001 from 2θ = 4.20◦ (21.02 Å) to 2θ = 3.24◦ (27.26 Å) is observed probably due to the formation of a secondary layered structure with some galleries intercalated by the PAA-SS/CTAB complex (Figure A10)
The most likely stabilization mechanism is the electrosteric one resulting from the effective adsorption of anionic PAA on the positively charged nanoclay surface
Summary
The contamination of water has become a critical problem due to potential health concerns [1]. Many processes can be used for the removal of pollutants from water. Adsorption is one of them, and a large number of novel adsorbents, such as polymer/nanoclay composites (PNC), have been developed in recent years. PNC are characterized by large surface area, high adsorption capacity and an excellent life cycle for water treatment, effectiveness and remediation potential, as well as their relatively low cost and toxicity [2]. It should be emphasized that PNC are used in many industries where conventional, monolithic materials do not show satisfactory properties or are characterized by too high own weight. Before the successful preparation of such materials, preliminary research concerning the interactions between potential components of PNC should be conducted
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