This article reviews the progresses on polymer membranes embedded with novel inorganic nanomaterials to provide micro reaction locations (MRLs) in the polymer matrices for wastewater treatment. Ultrafiltration (UF) membranes, especially polyvinylidene fluoride (PVDF) and polysulfone (PSF) membranes, are broadly applied in wastewater treatment. The strategy of embedding functional nanomaterials into the polymer matrices has been extensively investigated to enhance the integrated properties of polymer membrane. Nevertheless, the performance enhancement just comes from physical interactions between nanomaterials and wastes, while the chemical interactions are not involved, thus limiting further improvements. In order to further enhance the integrated properties of polymer membranes, functional inorganic nanomaterials that can chemically react with the wastes are proposed and embedded into the polymer membranes to form many MRLs. In this paper, the strategies for embedding functional nanomaterials such as sulfated TiO2 deposited SiO2 nanotubes, solid superacid porous ZrO2 shell/void/TiO2 core particles and porous YxFeyZr1-x-yO2 coated TiO2 solid superacid nanoparticles in polymer membranes were presented and the enhancement effect of MRLs on their integrated properties for wastewater treatments was discussed. Therefore, polymer membranes embedded with functional inorganic nanomaterials with MRLs are potentially applied in various wastewater treatments.

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.

Recently, zero-valent tungsten (W0) has been applied as a new zero-valent metal to degrade pollutants by the activation of H2O2, peroxydisulfate and peroxymonosulfate to generate •OH or SO4•–. However, the direct pollutant degradation by W0 without external oxidants has not been investigated yet. In this work, Methyl Orange was directly degraded by W0 without any external oxidants, even dissolved oxygen. The degradation followed first-order kinetics, and kobs showed an approximately linear correlation with W0 dosage. An acidic condition (pH 2) led to a higher degradation rate (0.162 min-1) and simultaneously a lower metal leaching (2.7 mg/L). SEM and XRD confirmed the unchanged morphology and crystalline structure of W0 after reaction, while the oxide shell was found more stable in the acidic condition, supported by higher W6+ content observed by XPS. Both •OH and O2•– were detected by ESR, but radical scavenging experiments excluded •OH as the main reactive species. By contrast, O2•– and electrons had a higher contribution. The O2•– was dependent on the dissolved oxygen while electrons were not, and thus the degradation occurred efficiently in the anaerobic condition. This work provides opportunities for a greener wastewater treatment process and supplementary understandings of the oxidant-involved processes.

This study describes the industrial use of waste generated from the brewing industry, specifically sludge from a wastewater treatment plant. The processing technique was developed to produce ceramic material with the potential for use as a lightweight aggregate in construction. This waste is usually dumped in landfills, but the current increase in restrictions on dumping and interest in improving the environment make our proposal for gaining value from this sludge a significant contribution. The chemical composition of the raw materials was analyzed (using X-ray fluorescence and elemental analysis) and their thermal behavior evaluated (thermogravimetric analysis and differential thermal analysis). To determine the effect of adding sludge to the aggregate, different compositions were then prepared and tested. To obtain the material’s final resistance and cohesion, the dried sample was subjected to a firing process in a kiln. The samples were prepared without special pre-treatment steps, such as milling, and without the addition of expansive additive. The new aggregate has a low bulk density, due to the formation of an internal cellular structure, a porous internal and a partially vitrified external shell. As waste is added, water absorption increases by values of 17–26 %, as does the porosity, resulting in a linear relationship between the pore volume and percentage of sludge added.

Membrane biological reactors (MBR) constitute an alternative to conventional wastewater treatments for improved recovery, reuse, and recycling of water. MBRs have a smaller footprint, provide better biotreatment and achieve a high-quality effluent. This work analyses the use of MBRs innovative low-cost ceramic membranes for wastewater treatment. We propose low-cost ceramic membranes as an alternative to the more expensive commercial ceramic membranes. Low-cost membranes were made of clay, calcium carbonate, potato starch, almond shell and chamotte. We synthesized two different selective layers, from clay and/or TiO2. We characterized the membranes (pore diameter and water permeance) and their performance in a laboratory scale MBR. To mitigate membrane fouling and preserve the continued operation along time, the effect of different operating cycles was measured, considering two physical cleaning strategies: relaxation and backwashing. Cycles of 9 min of operation, 30 s of relaxation and 1 min of backwashing provided the lowest fouling rate. We investigated the effect of air scouring on fouling by operating with different air flow rates. Once experimental conditions were optimized, the overall performance of the different ceramic membranes was tested. The membrane with a TiO2 thin layer provided the best resistance to fouling, as well as a good retention capacity of E. coli, Cryptosporidium oocysts and Giardia cysts.

The cost-effective and energy-efficient removal of organic micropollutants (MPs) from water and wastewater is challenging. The objective of this research was to evaluate the performance of porous β-cyclodextrin polymers (P-CDP) as adsorbents of MPs in aquatic matrixes. Adsorption kinetics and MP removal were measured in batch and flow-through experiments for a mixture of 83 MPs at environmentally relevant concentrations (1 μg L-1) and across gradients of pH, ionic strength, and natural organic matter (NOM) concentrations. Performance was benchmarked against a coconut-shell activated carbon (CCAC). Data reveal pseudo-second-order rate constants for most MPs ranging between 1.5 and 40 g mg-1 min-1 for CCAC and 30 and 40000 g mg-1 min-1 for P-CDP. The extent of MP removal demonstrates slower but more uniform uptake on CCAC and faster but more selective uptake on P-CDP. Increasing ionic strength and the presence of NOM had a negative effect on the adsorption of MPs to CCAC but had almost no effect on adsorption of MPs to P-CDP. P-CDP performed particularly well for positively charged MPs and neutral or negatively charged MPs with McGowan volumes greater than 1.7 (cm3 mol-1)/100. These data highlight advantages of P-CDP adsorbents relevant to MP removal during water and wastewater treatment.

Advanced oxidation processes can counteract the hazardous effects of polluted effluents in a highly efficient way, in many cases limited by the adsorption capacity of the nanocatalyst that depends on their size, internal structure and coating. Here, magnetic iron oxide nanocatalysts consisting on single core (SC), multicore (MC) and core-shell (CS) structures, stabilized with citrate and silica, have been evaluated for the degradation of anionic acid orange 8 (AO8) and cationic methylene blue (MB). It was observed that the adsorption is a limiting parameter, as expected in a mainly heterogeneous process involving molecular adsorption, reaction, and desorption at the catalyst surface. Thus, for the anionic dye, AO8, no degradation is observed by any of the nanocatalysts considering their negative surface charge. However, for MB loaded SC or CS nanocatalysts, highest degradation yields (almost 100% after 180 min at 90 °C) were achieved through a homogeneous and heterogeneous catalysis in the case of SC and a pure heterogeneous process in the case of CS. MC presents the lager aggregate size due to the lack of coating and low surface charge, leading to poor capacity of adsorption and degradation. On the other hand, magnetic induction heating promotes the degradation of MB (up to ≈50%, respect to room temperature). The results show that iron oxide nanocatalysts through Fenton reactions are an interesting alternative for wastewater treatment considering also that iron is non-toxic and one of the most abundant elements on Earth and can be recovered simply by applying a magnetic field.

Hexazinone, a globally applied broad-spectrum triazine herbicide, has not been mechanistically investigated previously under advanced oxidation processes (AOPs) and adsorption on activated carbon. In this study, its fate during UV-based oxidation with/without hydrogen peroxide (H2O2) and adsorption on coconut shell–based granular activated carbon (CSGAC) in water matrices was investigated. A comparison between various irradiation sources (visible, UVA, UVB, and UVC) revealed the highest degradation rate under UVC. More than 98% degradation of hexazinone was observed under 3 J cm−2 UVC fluence in the presence of 0.5 mM H2O2 at pH 7. Moreover, the degradation rate enhanced significantly with an increase in the initial dosage of H2O2, UV fluence, and contact time in the UV/H2O2 process. The rate of degradation was lower using secondary effluent than that of Milli-Q water due to the presence of dissolved organics in wastewater. However, the reactions in both matrices obeyed pseudo-first-order kinetics. The effect of different scavengers, including methanol, potassium iodide (KI), and tert-butyl alcohol (TBA), showed that hydroxyl radicals (•OH) played a dominant role in hexazinone degradation in the UV/H2O2 process. Hexazinone was effectively adsorbed by CSGAC through π-π electron donor–acceptor interactions between hexazinone’s triazine ring and CSGAC’s surface functional groups. The isotherm and kinetic studies showed that the adsorption followed the Freundlich model and pseudo-second-order reaction, respectively, suggesting chemisorption. This study provided mechanistic insights on the removal of hexazinone at the tertiary stage of wastewater treatment or the advanced treatment of wastewater reuse.

Silica@polymer spheres with a core@shell structure were synthesized and thermally annealed at 800 ºC to obtain silica@carbon spheres (SiO2@CSs). The silica core was removed by etching with NaOH, hollow carbon spheres (CSs) being obtained. The particle size of SiO2@CSs and CSs increased with the ethanol/water (E/W) volumetric ratio (2, 4.5, and 7) employed in the first synthesis step (i.e., the Stöber's method to obtain silica particles). Moreover, the average diameter of the materials prepared with E/W ratio of 2 was affected by the etching of the SiO2 core (from 168 to 109 nm), in contrast with those synthesized at higher E/W ratios of 4.5 and 7 (251–245 and 270–284 nm, respectively). The specific surface area (SBET) of the CSs ranged from 271 to 602 m2 g−1, which are more porous than SiO2@CSs (SBET in the range 115–144 m2 g−1). Adsorption kinetic and equilibrium studies were carried out with diclofenac and venlafaxine as model organic micropollutants (OMPs). Despite the silica removal was not effective for all the CSs (TGA residue ranging from 3 to 46 wt%), the kinetic studies and the ATR-FTIR spectra confirmed the positive effect of having a hollow core (i.e., removing the silica core). Equilibrium studies demonstrated that CSs prepared with an E/W ratio of 7 were the best performing material when considering both OMPs. Moreover, these CSs performed well to remove a set of 24 OMPs from wastewater effluents and thus, they are an interesting option for water or wastewater treatment.

Wastewater treatment plants (WWTPs) use granular activated carbons (GACs) as odor retainers because of their high surface area and porosity. The volatile compounds retained in these GAC beds saturate their pores and are periodically replaced by pristine GACs, which are frequently made from biomass materials such as coconut shell. Here, in order to recycle these exhausted GACs and reuse them again as adsorbents in a WWTP, a thermal regeneration of these wastes is proposed. Aiming to achieve more efficient and cleaner production, the pros and cons of using an oxidizing versus an inert atmosphere are evaluated. This work demonstrates that a simple thermal process at temperatures no higher than 350 °C for 1 h using an oxidizing atmosphere can achieve the regeneration of exhausted GAC with the appropriate characteristics for reuse as an adsorbent for gaseous emissions in a WWTP, evidencing a lower cost against a regenerative process in an inert atmosphere (about 20% lower in an oxidizing atmosphere). Their specific surface area and micropore volume values are around 475 m2/g and 0.264 cm3/g, respectively, which are in the range of characteristics of pristine GAC (406 m2/g and 0.229 cm3/g). The best regeneration yield was 96.8% for the SL-300-N2 sample. Interestingly, a regeneration at 900 °C using an inert atmosphere allows for the production of GACs with optimized textural properties (SBET ≈ 675 m2/g), a dual system of micro/mesopores (Vt ≈ 0.4 cm3/g and Vmicro ≈ 0.27 cm3/g), and also a regeneration efficiency of 90.5% for SL-900-N2, which would make it a raw material of interest for applications with more stringent requirements.