In this work, various physicochemical characteristics, e.g., surface properties and mineralogical compositions, of five clays collected from different sites in the Al-Hasa oasis in Saudi Arabia have been investigated. Analysis of the mineralogical compositions of the clays in the study by X-ray diffraction indicated the coexistence of palygorskite, montmorillonite, illite, kaolinite, chlorite, calcite and quartz in different percentages. Thermogravimetric analysis indicated that all studied clays exhibited dehydroxylation temperatures higher than 470 °C. On the other hand, pore size distribution analysis of clays from N2 adsorption indicated the presence of micro- and narrow mesopores (of 1.3–2.8 nm). Furthermore, the capability of the different clays for removal of Pb (II) from aqueous solution has been studied. The adsorption process was described through the Langmuir, Freundlich, Temkin and Dubinin–Radushkevich models. The Langmuir model was the most suitable compared to the other models in the case of palygorskite- and montmorillonite-rich clays. However, the Temkin model better represented the adsorption process of Pb (II) on calcite-rich clay. The clay sample with 61.0 wt% of palygorskite was found to be the most effective at removing Pb (II), with a maximum removal capacity of 74.07 mg/g at pH 6, with a contact time of 6 h and at 25 °C. Generally, the adsorption mechanism of lead over all the studied clays followed the pseudo-second-order kinetics. On the other hand, the catalytic activity of clays in the study has been tested in methanol conversion. The acidic clays, those containing high amounts of montmorillonite, showed higher selectivity to ethylene, viz., 78.9%, with a methanol conversion of 39.1% at 350 ° C and 0.1 MPa.

With poor irrigation water quality, cultivation difficulties are certainly expected to rise. This will cause a severe reduction in crops yield unless a strong strategy is followed to control and sustain high yielding capacity under particular circumstances. Water salinity presented in the form of water electrical conductivity (EC), has been presented in this study as one of the parameters that significantly participated in decreasing the quality of irrigation water in Al-Hassa oasis at Kingdom of Saudi Arabia. The sharing factors in quantifying water EC and its distribution spacewise has been examined by applying the frequency ratio (FR) technique (spatial autocorrelation) between salinity status and water measured elements, specifically, chlorine (Cl-), sodium (Na +), calcium (Ca 2+), potassium (K +) and magnesium (Mg 2+). A threshold salinity value of (EC ≥ 2.0 dS/m) was identified as a break-line for classifying the well-water sources that non-valid for irrigating vegetables grown in the area. A statistical correlation among the examined parameters and EC was conducted using the statistical package for social sciences (SPSS), and compared to the applied FR technique. A dosage of Clin irrigation water was observed to be the most significant candidate that raised EC, proved by an R 2 of 63%. However, the FR technique has shown the validity in analyzing the spatial distribution of water measured variables; in addition to nominating the variable that had the higher association portion, which was assessed to be Na + , followed by Clwith prediction rates of 4.22 and 3.22, respectively.

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