Liang Cheng

The application of metal–organic frameworks (MOFs) toward the adsorption of organic pollutants from aqueous systems has attracted heightened attention in recent times. While considerable research works have examined high-surface-area MOFs, growing evidence demonstrates that MOFs with low Brunauer–Emmett–Teller (BET) surface areas (S_BET ≤ 100 m²/g) can also achieve remarkably high pollutant adsorption. This review critically examines, for the first time, recent developments that have enabled low-surface-area MOFs to adsorb organic pollutants from wastewater efficiently. The first part explores compositional modifications of low-surface-area MOF adsorbents, with particular attention to their metal centers. Furthermore, four categories of auxiliary components were delved into. Additionally, the factors influencing adsorbent synthesis were presented. Moreover, low- and high-S_BET MOFs were directly compared. Finally, current challenges and key research gaps were identified. Future research priorities such as rigorous mechanistic validation, performance evaluation in realistic water matrices, improved regeneration strategies, and advancing pilot-scale studies to facilitate practical application were also presented.

Plant-based biocementation via enzyme-induced carbonate precipitation (EICP) presents a promising alternative to conventional soil stabilisation. Crude urease extracted from soybeans contains substantial organic matter, which can reduce its effectiveness for soil stabilisation. This study investigates the extraction and purification of soybean urease for stabilising crushed rock base (CRB) material in road construction. A calcium sulphate (CaSO₄) salting-out method was proposed and compared with conventional purification techniques, including filtration and centrifugation, in terms of organic matter removal, turbidity reduction and calcium carbonate (CaCO₃) precipitation behaviour. The purified enzyme was subsequently applied to CRB under varying soybean concentrations, cementation solution (CS) concentrations, and treatment cycles. Mechanical performance of CRB-treated samples was assessed using unconfined compressive strength (UCS) testing, while microstructural characteristics were examined using scanning electron microscopy (SEM) and X-ray diffraction (XRD). Results show that CaSO₄ salting-out effectively removes excess organic matter while maintaining enzymatic activity for EICP, enabling enzyme recovery without energy-intensive centrifugation at practical soybean concentrations. Although the CaSO₄ salting-out enzyme produced lower total CaCO₃ mass than less-refined extracts, it achieved more uniform precipitation and improved strength efficiency per unit of CaCO₃. The controlled addition of skim milk further enhanced the compressive strength without affecting urea conversion. SEM revealed irregular and spherical CaCO₃ particles from all urease extracts, while skim milk addition promoted spherical deposition around and in between the CRB particles. XRD confirmed calcite as the main phase governing strength development.

This study investigates the effect of welan gum (WG) on the workability of self‐compacting concrete (SCC) and further evaluates its improvements in compressive strength, durability, and air‐void structure. A series of tests were conducted on fresh cement pastes and SCCs with five WG dosages ranging from 0.01% to 0.1% (weight percentage with respect to binder mass), allowing for their flowability and stability. Using the suggested WG dosages, durability tests containing freeze–thaw (FT) cycle, concrete carbonation, and chloride permeability were carried out to seek a satisfactory WG content for SCC. The results show the cement pastes with both water‐reducing agent (WRA) and WG exhibited a large spread diameter of 226–242 mm and a low bleeding rate from 2.13% to 2.56% at WG contents of 0.025%–0.05%. Similarly, under the same WG dosages, SCCs exhibited a high slump‐flow of nearly 630 mm and a sound segregation rate varying from 3.51% to 6.35%. The compressive strength of SCCs increased by 5.29% at 0.05% WG. All durability tests approved that the SCC with 0.025% WG exhibited superior resistances. The three‐dimensional polymer–cement network and uniformly distributed air‐void system could account for the enhancement due to WG in workability, compressive strength, and durability of SCC. All above findings could offer reliable advice on preparing SCC with superior comprehensive performance using a WG dosage of approximately 0.025% by binder mass.