A new geopolymer adsorbent based on papermill sludge was prepared in the form of powder and granules and its efficiency for removing ammonium nitrogen from aqueous solution was investigated using batch and column adsorption experiments. The geopolymer was characterized by XRD and XRF. During adsorption tests, an influence of contact time, initial concentration, and adsorbent concentration on ammonium nitrogen removal were studied with powdered form of material. The maximum adsorption capacity of adsorbent towards ammonium nitrogen removed from model solution was found to be 36 mg/g when the adsorbent dose was 2 g/L and pH 7.4, respectively. Synthetic water as well as municipal wastewaters pretreated by flocculation and sedimentation techniques were used in order to prove efficiency of material in a complex matrix. Results obtained indicate that the new geopolymer composition is a promising low-cost material for ammonium nitrogen removal. It has been shown over continuous column experiments that exhausted adsorbent granules could be regenerated with different regeneration agents.

The European Union has an ambitious goal to transition from linear to circular economy [1]. In circular economy, the old saying of "one's waste is the other's treasure" is being implemented. An industrial side stream, traditionally branded as waste, is the raw material for the formation of the next product. Analcime is a reject from spodumene refining at a Finnish lithium hydroxide plant, currently in piloting stage, but is also found as a natural zeolite. With a channel size of 4.2-8.9 Å [2], analcime can be used as sodium cation exchange for NH4 + [3], Pb 2+ and Cu 2+ [4], and to a lesser extent and at elevated temperatures for K + , Ag + , Tl + , Rb + [5]. Being an energy minimum, the α-analcime structure is inert towards mild activation methods. Therefore, in this paper the valorisation of analcime by thermal and chemical activation and possible ways of obtained materials' use are discussed. Several procedures were considered in order to change raw material properties: alkaline, acid, and thermal activation. Raw analcime is inert towards alkaline activation (geopolymerisation) under all room temperature reaction in a solid to liquid ratio of 1:1.1 with NaOH/NaSiO3 or KOH/KSiO3 solution. Rinsing with 1 and 2 M HCl did not facilitate the geopolymerization, nor did heating at 700 °C. Calcination at 900 °C for 2 h resulted in complete phase change from analcime to nepheline, as characterized by XRD. Treating analcime with sulfuric acid of at 3, 4, and 5 M strength resulted in breakdown of the alumino-silicate structure of analcime and the formation of Na2AlSO4. XRD and XRF confirm the preferential dissolution of aluminate. After acid activation, geopolymerization occurred rapid and exothermic. Mixing analcime with metakaolinite as an additional binder had also resulted in the geopolymerized solid material. The structural properties, XRF, and XRD characterization of activated analcime products are discussed. Adsorptive properties of the new materials were tested for ammonium and compared to the raw side stream analcime. In all cases, the ammonium sorption were low. Activation with 5 M H2SO4 and subsequent geopolymerization (adsorbent ANA-5M-GP) doubles the adsorption capacity at 50 mg/L NH4 + and dose of 2 and 5 g/L. The competition of ion exchange sites Ca 2+ cations at concentrations found in municipal wastewater (40-100 mg/L Ca 2+) is discussed and investigated under complex matrix of Kajaani municipal waste water. Inert analcime side stream can undergo harsh chemical and thermal treatment to form new products with potentially interesting properties. Geopolymerization of acid treated activation of inert analcime greatly influences the structural and chemical properties of the raw substance. ANA-5M-GP has a higher adsorption capacity for ammonium than raw analcime. Additionally, the fast geopolymerization reaction could find applications in fast-hardening low carbon concrete substituents. Acid activation with at least 3 M H2SO4 therefore valorises the side product and enhances its properties for new applications...

Abstract. The formation and crystal structures of bis(1-naphthyl) diselenide (1) and bis{ [2-(N,N-dimethylamino)methyl]phenyl} tetraselenide (2) are described. Whereas 1 can be produced in good yields, 2 is formed only as a minor product together with the known main product, bis{[2-(N,N-dimethylamino)methyl]phenyl} diselenide. The composition of the reaction mixture is semi-quantitatively estimated by 77 Se NMR spectroscopy and DFT calculations. The effect of the

The EU has the ambitious goal to transition from linear to circular economy. In circular economy, the old saying of “one’s waste is the other’s treasure” is being implemented. In this chapter, valorisation of industrial side streams, traditionally branded as waste, is discussed with respect to their applications as raw materials for new adsorptive products – geopolymers (GP) and alkali-activated materials (AAM) – as adsorbents in wastewater treatment. The chemical nature and structure of materials generally have great influence on GP/AAM adsorption capability. The approaches used for the raw materials preparation (chemical or physical) prior geopolymerization to increase the adsorption capacity of the final products will be discussed. Adsorption properties and performance of GPs/AAMs towards various contaminants are described, and the latest research on testing those materials as water remediation are reviewed. Special attention is paid to regeneration of exhausted materials and available resource recovery options that the regeneration approach opens. New forms of geopolymer adsorbent such as foams or core-shell structures are described and in the last part of the chapter, a short economic evaluation of resource recovery models is provided.

The environmental and economic benefits of recycling spent Nd-Fe-B magnets are becoming increasingly important. Nevertheless, the reprocessing of this type of material by conventional processes remains a challenge due to the difficulties of rare earth elements (REEs) and Fe separation, low products purity and large-scale generation of boron wastewater. This research presents an effective approach for the comprehensive recovery of REEs, iron and boron from Nd-Fe-B magnet wastes. Investigations of the initial roasting pretreatment showed it to be an effective method that aids the subsequent selective separation of REEs, with the most suitable temperature determined to be 800 °C. During the following selective hydrochloric acid pressure leaching of the roasted magnet, the addition of 2 g/L NaNO 3 was found to significantly improve the separation of REEs and B from Fe. The results indicated that almost 99% of REEs and 97% of B could be extracted, whilst in contrast, less than 0.1% of iron dissolved, to leave a hematite rich residue. The extracted REEs were then directly precipitated as oxalates with >99% extraction and 99.95% purity at a value n(oxalic acid)/n(REEs) of 1, resulting in significant improvements to oxalic acid consumption and REEs product purity. In the final step, 99.5% of boron was recovered via a three-stage counter current extraction with 30% (v/v) (EHD) and 70% (v/v) sulfonated kerosene. These findings demonstrate that high recoveries of REEs, Fe and B are achievable with hydrochloric acid pressure leaching followed oxalate precipitation and boron recovery.