Emerging Contaminants and Their Removal from Aqueous Media Using Conventional/Non-Conventional Adsorbents: A Glance at the Relationship between Materials, Processes, and Technologies

Abstract

Emerging contaminants (ECs) are causing negative effects on the environment and even on people, so their removal has become a priority worldwide. Adsorption and the associated technologies where this process occurs (filtration/biofiltration) have gained great interest, due to its low cost, easy operation, and effectiveness mainly in the removal (up to 100%) of lipophilic ECs (log Kow > 4). Activated carbon continues to be the most efficient material in the removal of ECs (>850 mg/g). However, other conventional materials (activated carbon, clays, zeolites) and non-conventional materials (agro-industrial/forestry/industrial residues, nanomaterials, among others) have shown efficiencies greater than 90%. Adsorption depends on the physicochemical properties of the materials and ECs. Thus, physical/chemical/thermal modifications and nanomaterial synthesis are the most used procedures to improve adsorption capacity. A material with good adsorptive properties could be used efficiently in filtration/biofiltration technologies. Agro-industrial residues are promising alternatives to be used in these technologies, due to their high availability, low toxicity, and adsorption capacities (up to 350 mg/g). In filtration/biofiltration technologies, the material, in addition to acting as adsorbent, plays a fundamental role in operation and hydraulics. Therefore, selecting the appropriate material improves the efficiency/useful life of the filter/biofilter.

Efficient Decontamination: Caffeine/Triclosan Removal using Rice Husk in Batch and Fixed-Bed Columns

“…The removal of emerging contaminants (ECs) is a topic of growing significance in environmental management and public health [1]. These contaminants, which include substances such as antibiotics and disinfectants, have gained even greater importance in recent years due to global events such as the COVID-19 pandemic.…”

“…The residues of these substances are considered ECs [3]. ECs are pseudo-persistent organic substances found in low concentrations in the environment (ng/L-mg/L) [1]. They exhibit low concentrations, wide variety (100,000 chemical substances) [1] and different physical-chemical characteristics (solubility, volatility, bioaccumulation capacity, etc.).…”

“…ECs are pseudo-persistent organic substances found in low concentrations in the environment (ng/L-mg/L) [1]. They exhibit low concentrations, wide variety (100,000 chemical substances) [1] and different physical-chemical characteristics (solubility, volatility, bioaccumulation capacity, etc.). They exhibit low removal in conventional wastewater treatments: for instance, ibuprofen has 32.8% and diclofenac has no removal when treated with activated sludge at the laboratory scale [4].…”

“…They exhibit low removal in conventional wastewater treatments: for instance, ibuprofen has 32.8% and diclofenac has no removal when treated with activated sludge at the laboratory scale [4]. This opens the possibility for ECs to reach water bodies and enter the food chain [1].…”

“…About 5% of ingested caffeine is not metabolized and is excreted in the urine [5]. Thus, it has been frequently found in different water bodies (surface water: 3-1500 ng/L, groundwater: 10-80 ng/L), wastewater (20-300 µg/L), and effluents from wastewater treatment plants (0.1-20 µg/L) [1]. Moreover, caffeine and its metabolites are not volatile substances, which makes them persistent (3-6 weeks under natural mineralization) in water bodies, generating toxic effects in biota and the surrounding aquatic environment [6].…”