Pd-ZnO nanoparticles decorated acid activated montmorillonite for the efficient removal of cationic dyes from water

Effective removal of malachite green from local dyeing wastewater using zinc-tungstate based materials

“…In all, a multilayer coverage on the heterogenous surface of the nanoadsorbents was confirmed, indicating improvement in interactions between MG dye molecules and ZnWO 4 /ZnWO 4 @BCN/N. A similar result has been reported by previous studies [ 36 , 49 , 70 ].…”

“…The pH of the solution is an important parameter in determining a nanoadsorbents adsorption capability because it provides information on the acidity and alkalinity of the adsorption media. Overall, the pH of the solution affects the surface charge of the nanoadsorbent and the dissociation/ionization of functional groups found on the surface of the nanoadsorbent and in the dye (H + /OH − competition) [ 36 , 70 ]. The influence of solution pH on the uptake effectiveness of MG from local dyeing wastewater was explored and the corresponding results are shown in Fig.…”

“…This indicates that the surface of the nanoadsorbents was positively charged at the pH below 6.0 and 6.8, but negatively charged at the pH above 6.0 and 6.8, respectively. In this case, a large number of protons are produced in the solution at pH < pH PZC , thereby causing electrostatic repulsion between cationic MG and the positively charged surface of the ZnWO 4 /ZnWO 4 @BCN/N [ 70 , 72 , 73 ]. On the other hand, as the pH value increased towards and exceeded the pH PZC of the nanoadsorbents, the positive charges on the nanoadsorbents decreases and gradually turns to negative charges beyond the pH PZC , thus increasing the electrostatic attraction of negatively charged ZnWO 4 /ZnWO 4 @BCN/N to positively charged MG [ 47 , 74 ].…”

“…On the other hand, as the pH value increased towards and exceeded the pH PZC of the nanoadsorbents, the positive charges on the nanoadsorbents decreases and gradually turns to negative charges beyond the pH PZC , thus increasing the electrostatic attraction of negatively charged ZnWO 4 /ZnWO 4 @BCN/N to positively charged MG [ 47 , 74 ]. Generally, MG exists in three basic forms chromatic MG, carbinol base and leuco MG, which decolorizes and precipitates as a carbinol base at pH > 10.5 [ 70 ]. From this study, it was concluded that neutral to basic environments provided the optimum conditions for the removal of MG from local dyeing wastewater.…”

Comparative study on ionic dissolution and structural changes of montmorillonite, kaolinite, and muscovite during interfacial reactions with oxalic acid solution

“…Figure 5 shows the FT-IR spectra of montmorillonite, kaolinite, and muscovite as well as their products after 150 and 300 days of the reaction with oxalic acid. In Figure 5a, the peaks at 3435 and 1641 cm -1 in the spectrum of montmorillonite caused by the H2O stretching and bending vibrations in adsorbed and interlayer water in the sample (Deepika and Sethuraman, 2023).…”