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Clays are used for the construction of waste containment barriers, because of its low hydraulic conductivity. Due to the difficulty in obtaining the natural clay satisfying the essential requirement as a liner material; commercially available bentonites are being used for the construction of clay liners. Bentonite undergoes large volume changes upon saturation. Various physical and chemical stabilisation techniques are in practice to stabilise the bentonite. Previous studies reported that contaminants with high concentrations attack clay minerals leading to increase in their permeability. Exfoliated vermiculite, finds several applications in construction industry, also found to be good absorbent material. Hence, this study has been carried out to find the optimal percentage of vermiculite that can be added to the bentonite so that it satisfies the essential requirements of clay liners and absorb the heavy metals from contaminants. Several index properties and engineering properties tests on bentonite-vermiculite mixtures were performed. From the studies, it was found that 30% of vermiculite can be added to bentonite, so that the essential requirements of liner can be maintained.

Two‐step solar thermochemical water splitting is a promising pathway for renewable fuel production. Among the state‐of‐the‐art materials, ceria tends to favor the oxidation step while perovskites favor the reduction step and developing a champion material with well‐balanced redox thermodynamics remains a key challenge. A generic thermodynamic framework is thus presented to guide material design. More details can be found in article number 2000925, Wojciech Lipiński and co‐workers.

Two‐step solar thermochemical water splitting is a promising pathway for renewable fuel production due to its potential for high thermal efficiency via full‐spectrum sunlight utilization. Such a promise critically relies on simultaneous innovation in the redox materials and the reactor systems. Most prior efforts on material design are focused on improving the fuel yield at lower reduction temperatures. However, developing materials with both high fuel output and efficiency remains a key challenge, requiring a rigorous understanding of the effects of material thermodynamic properties. Herein, a generic thermodynamic framework is described to decipher the material effects by studying both the state‐of‐the‐art and hypothetical materials within a counterflow reactor system. A global efficiency map is presented for redox materials, revealing inevitable tradeoffs among competing factors such as thermal losses, sweep gas and oxidizer demand, solid preheating, and reduction enthalpy. The choice of the most efficient material is closely linked to the system conditions. Ceria‐based materials outperform perovskites under most scenarios, and the optimal hypothetical materials tend to favor higher reduction enthalpies and entropies than existing materials. This work offers a valuable material design roadmap to identify solutions toward efficient solar fuel production. A global thermal efficiency map is presented for different redox materials that reveals fundamental trade‐offs among competing factors for solar thermochemical fuel production. Both state‐of‐the‐art and hypothetical materials are investigated within a counterflow reactor system. An optimal material regime exists leading to peak efficiency, and the critical efficiency‐limiting energy factors of nonideal materials are also identified.