The remediation of water streams, polluted by various substances, is important for realizing a sustainable future. Magnetic adsorbents are promising materials for wastewater treatment. Although numerous techniques have been developed for the preparation of magnetic adsorbents, with effective adsorption performance, reviews that focus on the synthesis methods of magnetic adsorbents for wastewater treatment and their material structures have not been reported. In this review, advancements in the synthesis methods of magnetic adsorbents for the removal of substances from water streams has been comprehensively summarized and discussed. Generally, the synthesis methods are categorized into five groups, as follows: direct use of magnetic particles as adsorbents, attachment of pre-prepared adsorbents and pre-prepared magnetic particles, synthesis of magnetic particles on pre-prepared adsorbents, synthesis of adsorbents on preprepared magnetic particles, and co-synthesis of adsorbents and magnetic particles. The main improvements in the advanced methods involved making the conventional synthesis a less energy intensive, more efficient, and simpler process, while maintaining or increasing the adsorption performance. The key challenges, such as the enhancement of the adsorption performance of materials and the design of sophisticated material structures, are discussed as well.

The removal of Zn from wastewater generated from the Zn-based electroplating manufacturing process is essential because the regulation limit of Zn concentration in wastewater is becoming stricter in Japan. However, achieving this through conventional methods is difficult, especially for small and medium enterprises in the plating industry. Therefore, a suitable Zn-removal method with a low cost but high performance and Zn selectivity is required. The application of adsorbents is one possible solution. Mesoporous silica (MS) is a well-known adsorbent with controllable pore size, high specific surface area (SSA), high acid resistance, and ease of surface modification. In this study, we modified the surfaces of MSs with different initial pore sizes by amino groups and investigated their Zn removal performances. The effect of pore size on amine modification using (3-aminopropyl)triethoxysilane and on adsorption performance in a single system was investigated along with Zn adsorption selectivity in the Zn–Ni binary system. Amine-modified MS prepared from MS with an initial pore size of 1.9 nm showed drastically lower performance compared to those prepared from MS with an initial pore size larger than 2.8 nm. Zn-selectivity in the Zn–Ni binary system, containing equal amounts of Zn and Ni, was found to reach a maximum of 21.6 when modifying MS with an initial pore size of 2.8 nm.

This work utilized the simplicity of a so‐called membraneless vaporization (MBL‐VP) unit as a gas separator for the colorimetric determination of ethanol in alcoholic beverages. A beverage sample with a volume of 1 mL was directly injected into a small container which was hung from a lid inside a closed 40 mL reused glass bottle without pretreatment such as distillation. An acidified potassium dichromate (Cr₂O₇²⁻) acceptor solution, preadded to the glass bottle, was reduced to Chromium (III) ion by the diffusion of vaporized ethanol from the sample. After 5 min, the absorbing solution was collected for colorimetric detection at 590 nm. The unit manually quantifies ethanol in the range 1.0–90% (v/v) with satisfactory interday precision but without matrix effect (recovery 89−109%). The method was validated with the conventional distillation/pycnometer method which showed no significant difference of ethanol contents between those two methods and the declared values of 12 alcoholic beverages, indicating sufficient accuracy. Analyses of alcoholic beverages using this method were successful with benefits of simplicity, cheapness, and less energy consumption.