The utilization of phosphoric acid in various sectors, e.g., food industry, is controlled by the authorized concentration limit of impurities. However, industrial phosphoric acid is contaminated with undesirable impurities (such as F, Al, Fe, Mg, etc.). Herein, this study aimed to evaluate the efficiency of the membrane purification process of pretreated industrial phosphoric acid using a premodified nanofiltration membrane. We demonstrated that the prior pretreatment steps for industrial phosphoric acid allowed the elimination of sulfate, fluorine and arsenic. Further purification of the obtained pretreated phosphoric acid using membrane cells reduced the concentrations of Cd, Al, Fe and rare earth elements by 94.81, 99.30, 99.63 and 96.67%, respectively. The membrane is functionalized by a deposit of a high molecular weight polycationic polymer of polyethyleneimines in order to produce a highly charged membrane surface to enhance the separation efficiency, selectivity and stability of the membrane. We found that the purification process relies on electrostatic repulsion between the functionalized membrane and highly charged ions, and the reduction rate of metals is a cation charge-dependent parameter. The laboratory and industrial pilot scale results showed that this process allows the production of food-grade phosphoric acid.

Type II-S oil shale carries sulfur in thermolytically weak C–S and S–S linkages, causing H2S co-evolution that complicates conventional non-isothermal retorting. This work applies a four-stage (multi-stage) isothermal fractionation (MS-IF) protocol (100, 350, 550 and 850 °C) to a Jordanian Al-Lajjun oil shale under dry and steam-intensified atmospheres, benchmarked against single-stage pyrolysis coupled to real-time gas speciation with solid- and liquid-phase characterization. Thermogravimetric analyses of fresh, demineralized, Fe-spiked demineralized and Ca-spiked demineralized matrices were performed at multiple heating rates. When resolved by constrained Fraser-Suzuki deconvolution and validated by dual isoconversional methods (Friedman, Starink). Two organic devolatilization events (mass-weighted activation energy 170.6 kJ mol−1) were isolated from a diffusion-controlled carbonate-decomposition event that dominates the bulk mass-loss profile. The native mineral matrix lowers the organic activation energy by 20–30 kJ mol−1, while independently obtained (Ea, ln A) pairs reveal a kinetic compensation effect (isokinetic temperature ≈ 296 °C) explaining why calcium carbonate addition raises, rather than lowers, peak decomposition temperature despite reducing the barrier. Dry MS-IF achieves 8.7% more mass loss than single-stage pyrolysis at equal peak temperature, and resolves two mechanistically distinct H2S release windows around 380 °C and 450 °C. Steam co-feeding advances sulfur mobilization to lower temperature and drives a strong water-gas shift, increasing H2 yield up to 16-fold at high temperatures. Liquid condensates remain organosulfur-dominated (47–63%), with the 350 °C stage identified as sulfur-selective. These findings establish MS-IF as a mechanistic and process framework for decoupling volatile sulfur evolution and liquid organosulfur partitioning from hydrocarbon and syngas generation in high-sulfur oil shale valorization.