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Raw coal without carbonization was treated with sulfuric acid at different concentrations (70% to 95%) as a controlled sulfonation process to produce a simple and effective acidic catalyst. The synthetic catalyst (S.Coal) at the best H 2 SO4 concentration (95%) showed the best acid density (8.4 mmol/g), the best surface area (26.4 m2/g), and the best catalytic activity during the transesterification of the waste sunflower oil. The best yield (98.8%) at low-temperature conditions (40 °C) was achieved after 60 min using 3 g of the catalyst and at a methanol/oil ratio of 20:1. At high-temperature conditions (120 °C), the yield was enhanced to 99.5% after 30 min only considering the catalyst quantity and the methanol content as the same values. The S.Coal as a catalyst is of remarkable reusability for five transesterification runs either at low-temperature conditions (40 °C) or at high-temperature conditions (120 °C). Additionally, the catalyst is of higher catalytic performances than several basic and acidic catalysts demonstrate the efficiency of the sulfonation process on the raw coal without carbonization. The kinetic properties of the occurred transesterification reactions over S.coal followed the Pseudo-First order behavior and of low activation energy.

β-cyclodextrin/diatomite composite (β-C/D) was characterized as a potential carrier for the ibuprofen drug (IBU) with enhanced loading and release properties. The β-C/D carrier achieved experimental and theoretical loading capacities of 419 mg/g and 596 mg/g, respectively. The loading behavior follows the Langmuir equilibrium properties and the Pseudo-Second order kinetics. The loaded IBU molecules are of monolayer and homogeneous form and their loading processes involved physical and chemical mechanisms with dominant effect for the physical processes considering the Gaussian energy of value (6.96 KJ/mol). Based on the free energy (−16.9 to −17.4 KJ/mol) and enthalpy (−8.4 KJ/mol), the loading of IBU into β-C/D occurred by spontaneous, exothermic, and favorable reactions. The release profile of the IBU-loaded β-C/D extended for 200 h in the gastric fluid (95.4%) and 100 h in the intestinal fluid (100%). The IBU release rate can be controlled by adjusting the ratio of the incorporated β-cyclodextrin polymer in the composite. The release kinetic studies and the diffusion exponent values of the Korsmeyer–Peppas (0.62 (pH 1.2) and 0.58 (pH 7.4)) suggested release mechanism controlled diffusion as well as erosion processes but with essential effect for the diffusion of the drug. The cytotoxicity studies demonstrate safe and biocompatible effects for β-C/D and IBU-loaded β-C/D on human bronchial epithelial cells.

Chitosan/diatomite composite (CH/D) was synthesized at potential multifunctional adsorbent of enhanced uptake capacities for different species of organic water pollutants. The synthetic CH/D composite was characterized and applied in batch adsorption studies for pefloxacin (PF) as pharmaceutical residual and chlorpyrifos (CF) as pesticide residual from water. The CH/D composite is of enhanced uptake capacities for both PF (310.7 mg/g) and CF (392.2 mg/g) as compared to diatomite and chitosan and single components. The PF and CF uptake reactions follow the Langmuir model as an equilibrium model which demonstrates their adsorption in monolayer and homogenous form. The PF uptake process is of Pseudo-First order kinetic while the CF uptake process is of Pseudo-Second order kinetics. The Gaussian energies (6.74 KJ/mol (PF) and 7.76 KJ/mol (CF)) and thermodynamic parameters suggest PF and CF adsorption reactions of physical, feasible, exothermic, and spontaneous properties. The CH/D composite exhibits strong selectivity for PF and CF molecules in the existence of PO43−, SO42−, and NO3− anions and considerable selectivity for them in the coexistence of Zn2+, Cd2+, and Pb2+ metal cations. The CH/D composite is of remarkable recyclability and reused in the removal of PF and CF for five cycles with removal percentages higher than 86% and 89%, respectively.

Two types of NiO-based composites (NiO@diatomite and Ni/NiO@diatomite) were synthesized as modified products of enhanced catalytic performances during the transesterification reactions of waste cooking oil. The influence of the diatomite substrate and the integration of metallic Ni0 in inducing the catalytic activity were evaluated in a series of transesterification reactions. The experimental conditions were adjusted according to the response surface methodology and the central composite statistical design. Experimentally, the diatomite substrate and the Ni0 metal induced the efficiency of the reaction to achieve a yield of 73.4% (NiO@diatomite) and 91% (Ni/NiO@diatomite), respectively, as compared to 66% for the pure phase (NiO). This was obtained under experimental conditions of 80 °C temperature, 100 min time, 12:1 methanol/oil molar ratio, and 3.75 wt % loading. The theoretical optimization functions of the designs suggested enhancement to the experimental conditions to achieve a yield of 76.3% by NiO@diatomite and 93.2% by Ni/NiO@diatomite. This reflected the role of the diatomite substrate in enhancing the surface area, the adsorption of fatty acids, and the exposure of the catalytic sites in addition to the effect of the Ni0 metal in enhancing the catalytic reactivity of the final product. Finally, the biodiesel produced over Ni/NiO@diatomite as the best product was of acceptable properties according to the international standards.

Bentonite/zeolite-P composite (B/ZP) was synthesized by simple alkaline hydrothermal treatment at 150 °C for 4 h and characterized by different analytical techniques. The composite was introduced as a low-cost catalyst of enhanced physiochemical properties and catalytic activity in the transesterification of palm oil into biodiesel. The catalytic activity of B/ZP catalyst was inspected by normal stirring mixing and under ultrasonic irradiation of different powers (20–60%). The best biodiesel yield by normal stirring (96.2%) was achieved at operating conditions of 210 min as conversion time, 20:1 as a methanol-to-oil molar ratio, 5 wt% as a catalyst loading, 90 °C as temperature and 900 rpm as stirring speed. The conversion reaction under the ultrasonic irradiation (power 60%) gives biodiesel yield of 98.8% after 120 min as reaction time using 5 wt% as catalyst loading, 20:1 as a methanol-to-oil ratio, and 90 °C as temperature. The ultrasonic irradiation is of positive impacts in reducing the conversion time interval, reaction temperature, catalyst loading, and methanol-to-oil molar ratio with biodiesel yield similar to that obtained by normal stirring at its best conditions. The catalyst is of higher activities than several homogenous and heterogeneous catalysts and can be reused several times with high catalytic activity especially using an organic solvent either by normal stirring or under the ultrasonic irradiation. The physicochemical specification of the obtained biodiesel by both methods matches the requirements of STM D-6571 and EN 14214 international standards.

Chitosan/diatomite nanocomposite (CS/D) was synthesized as a low-cost and highly porous structure of enhanced physicochemical properties to be applied as advanced carriers for ibuprofen drug (IB). The loading properties of CS/D were studied in comparison to diatomite as a separated phase and achieved a loading capacity of 562.6 mg/g. The loading reactions of IB into CS/D show pseudo-second-order kinetic behavior and Langmuir isotherm properties. This demonstrates homogeneous loading processes in monolayer forms and controlled essentially by physical mechanisms. This was confirmed by the calculated Gaussian energy (7.7 kJ/mol (D) and 7.9 kJ/mol (CS/D)) in addition to the thermodynamic parameters. The thermodynamic behavior for the IB loading process is related to spontaneous, favorable, and exothermic reactions. The CS/D composite is of promising IB release profile that extended to about 200 h with a maximum release of 91.5% at the gastric fluid (pH 1.2) and 97.3% in the intestinal fluid (pH 7.4). The IB release rate from CS/D can be controlled based on the ratio of the integrated chitosan in the composite. The IB release reactions from CS/D follow the assumption of Korsmeyer–Peppas kinetics with determined values for the diffusion exponent reflects complex diffusion and erosion as the affected mechanisms during the IB release process.

The siliceous frustules of diatomite were integrated with β-cyclodextrin polymer in novel composite (β-CD/D) for enhanced retention properties for radioactive ions. The β-CD/D composite was characterized by different analytical techniques and applied in batch adsorption studies for the dissolved Cs+ and Ba2+ ions. The β-CD/D composite exhibits promising retention capacities (Cs+ (144.5 mg/g) and Ba2+ (195.7 mg/g)) which are higher than its components and other evaluated adsorbent in literature. The Cs+ and Ba2+ retention reactions by β-CD/D are of Langmuir properties, Pseudo-Second order kinetics, and Gaussian energies less than 8 KJ/mol. Therefore, the ions were adsorbed homogeneously in monolayer forms by physicochemical mechanisms involved in electrostatic attraction and the formation of chemical complexes. The thermodynamic parameters suggested spontaneous and exothermic behaviors for the occurred Cs+ and Ba2+ retention reactions. The synthetic β-CD/D is of significant affinities for the Cs+ and Ba2+ ions in the presence of competitive anions (HCO3−, SO42−, NO3−, and PO43−) and considerable affinitive in the presence of other metals (Cd2+, Pb2+, Zn2+, and Co2+). The β-CD/D composite also is a highly recyclable product and can be reused effectively in Cs+ and Ba2+ removal processes for five cycles.

A novel composite of muscovite/synthetic zeolite (phillipsite) (Mu/Pz) was synthesized in an open system by the alkaline modification at 150 °C under stirring of speed 600 rpm for 22 h. The composite was characterized as a novel, low cost and effective basic catalyst in the transesterification conversion of palm oil into biodiesel. The catalytic properties of Mu/PZ were studied based on several controlling factors by normal stirring and ultrasonic irradiation as mixing techniques. The maximum biodiesel yield obtained by normal stirring is 94% and was accomplished after adjusting the controlling factors at 180 min as conversion interval, 20:1 as the incorporated methanol-to-oil molar ratio, 100 °C as reaction temperature, 5 wt, % as a Mu/Pz loading and 1300 rpm as a stirring speed. The influence of ultrasonic irradiation was addressed within a range from power 20% to power 60% and the best results were achieved using ultrasonic power of 60%. At the same conducting conditions of temperature, Mu/Pz loading, and the incorporated methanol-to-oil ratio, the biodiesel yield attained 97.8% after 90 min by using ultrasonic irradiation as a mixing method at 60% power. The stability study of Mu/Pz catalyst revealed high reusability properties for five cycles using three regeneration solvents of distilled water, methanol and acetone with clear preferences for using the organic solvents. The specifications of the obtained biodiesel samples by both methods match the biodiesel requirements of the STM-D-6571 as well as the EN-14214 international standards.