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Alkali-activated materials are a low-CO2 alternative for Portland cement in construction. However, one major issue in their use is the poor or varying functionality of the currently available commercial superplasticizers. Especially for one-part (‘just add water’) alkali-activated materials, the number of studies is limited. In this study, one-part alkali-activated mortar was prepared from blast furnace slag by using solid sodium hydroxide as an activator and microsilica as an additional silica source. Comparison of commonly used superplasticizer types revealed that lignosulfonate, melamine, and naphthalene-based superplasticizers are more efficient than the currently most used polyacrylate and polycarboxylate-superplasticizers. Lignosulfonate-based superplasticizer was overall best-performing: it improved significantly the workability (+41% spread, −51% yield stress, −27% viscosity), setting time (+70%), and compressive strength (+19%) at a 0.5 wt% dose. When the amount of water and superplasticizer were optimized, compressive strength of mortar could be doubled (from 19 to 40 MPa at 28 d).

Ammonium (NH₄⁺) removal from municipal wastewater poses challenges with the commonly used biological processes. Especially at low wastewater temperatures, the process is frequently ineffective and difficult to control. One alternative is to use ion-exchange. In the present study, a novel NH4+ ion-exchanger, metakaolin geopolymer (MK-GP), was prepared, characterised, and tested. Batch experiments with powdered MK-GP indicated that the maximum exchange capacities were 31.79, 28.77, and 17.75 mg/g in synthetic, screened, and pre-sedimented municipal wastewater, respectively, according to the Sips isotherm (R² ≥ 0.91). Kinetics followed the pseudo-second-order rate equation in all cases (kp₂ = 0.04–0.24 g mg⁻¹ min⁻¹, R² ≥ 0.97) and the equilibrium was reached within 30–90 min. Granulated MK-GP proved to be suitable for a continuous column mode use. Granules were high-strength, porous at the surface and could be regenerated multiple times with NaCl/NaOH. A bench-scale pilot test further confirmed the feasibility of granulated MK-GP in practical conditions at a municipal wastewater treatment plant: consistently