Jordanian bentonite was activated by hydrochloric acid at room temperature. FTIR, XRD, TGA, and BET surface area analyses of the samples were carried out to examine the structure of bentonite before and after acid activation. It is found that the octahedral cations were removed, which altered the chemical composition of the bentonite. Difference of surface area was noticed (66.2 to 287.8 m² g⁻¹), which was caused by structural changes in the bentonite. We aimed to investigate the effectiveness of activated bentonite in OMWW treatment. Batch and column techniques were applied. Crude and treated OMWW samples were characterized; physiochemical parameters, total phenolic compounds, and heavy metal ions concentrations were measured. Several parameters that affected the adsorption capacity were studied: the pH value of the solution, temperature, and the adsorbent dose. It was found that the maximum removal of total phenolic compounds and heavy metal ions (Zn, Fe, and Mn) was at pH 6. Adsorption capacity of phenolic compounds was enhanced with an increase in the temperature of the solution and also with the adsorbent dose. The optimum adsorbent concentration needed for the maximum removal of total phenolic compounds is 1 g of activated bentonite/0.01 L of OMWW. The percentage removal exceeded 99% for Zn, Fe, and Mn ions, while it reached 65.2 and 61.5 for K⁺ and Na⁺ ions, respectively. Finally, the percentage removal of pollutants was increased by using activated bentonite. This study will provide valuable insight into the effect of activated bentonite towards the treatment and recyclability of OMWW, which is essential for the local olive mill industry.

Nanosized ceria (CeO₂) and a graphitic carbon nitride-loaded ceria (CeO₂/GCN) nanocomposite were synthesized using a straightforward and efficient method and characterized by XRD, FTIR, SEM, TEM, TGA, and BET analyses. These techniques confirmed that CeO₂ was effectively supported on the surface of GCN, with particle sizes of the CeO₂/GCN composite in the range of 10–15 nm and a pore size of 3.33 nm. The photocatalytic activity of the CeO₂/GCN nanocomposite and CeO₂ NPs in the degradation of methyl red dye under sunlight radiation was studied using UV–visible spectroscopy. A noticeable red shift in the CeO₂/GCN nanocomposite compared to pure CeO₂ NPs suggests a reduction in its band gap energy, calculated at 3.90 eV for CeO₂ NPs and 2.97 eV for the CeO₂/GCN nanocomposite. This band gap reduction enhances the photocatalytic degradation process, achieving a removal efficiency of 99.92% within a short irradiation time of 40 min for the CeO₂/GCN nanocomposite, compared to 69.47% for CeO₂ NPs. These findings indicate that graphitic carbon nitride significantly enhances the photocatalytic properties of CeO₂ NPs.

Kaolinite clay has low cation exchange capacity and small surface area; it has rarely been used as adsorbent. As well as, green, low cost and efficient adsorbent is desired. Modification of kaolinite is necessary to improve its adsorption capacity. Jordanian kaolinite has been modified by humic acid (HA) through batch adsorption mode. Two types of HA were used; one was commercial (FHA) and the other was natural (KTD). The effect of HA concentration, pH and temperature of solution were considered. HA adsorption becomes higher at low concentration, decreases with increasing pH, and it increased with solution temperature. Modified Jordanian kaolinite clay was characterized by different techniques: FTIR, TGA, SEM connected to EDS and porosimetry analysis by Gas Adsorption Isotherm and Mercury Porosimetry. The modified kaolinite showed good and strong interaction with HA, enhancement in its surface and charge structure, and increasing in the average pore radius. Therefore, increases in its reactivity and adsorption sites especially towards heavy metal ions. Moreover, FHA– kaolinite clay showed better adsorption characteristics than KTD– kaolinite clay.