Iron-loaded carbon black prepared via chemical vapor deposition as an efficient peroxydisulfate activator for the removal of rhodamine B from water.

The excessive use of organic pollutants like organic dyes, which enter the water environment, has led to a significant environmental problem. Finding an efficient method to degrade these pollutants is urgent due to their detrimental effects on aquatic organisms and human health. Carbon-based catalysts are emerging as highly promising and efficient alternatives to metal catalysts in Fenton-like systems. They serve as persulfate activators, effectively eliminating recalcitrant organic pollutants from wastewater. In this study, iron-loaded carbon black (Fe-CB) was synthesized from tire waste using chemical vapor deposition (CVD). Fe-CB exhibited high efficiency as an activator of peroxydisulfate (PDS), facilitating the effective degradation and mineralization of rhodamine B (RhB) in water. A batch experiment and series characterization were conducted to study the morphology, composition, stability, and catalytic activity of Fe-CB in a Fenton-like system. The results showed that, at circumneutral pH, the degradation and mineralization efficiency of 20 mg L-1 RhB reached 92% and 48% respectively within 60 minutes. Fe-CB exhibited excellent reusability and low metal leaching over five cycles while maintaining almost the same efficiency. The degradation kinetics of RhB was found to follow a pseudo-first-order model. Scavenging tests revealed that the dominant role was played by sulfate (SO4-˙) and superoxide (O2-˙) radicals, whereas hydroxyl radicals (OH˙) and singlet oxygen (1O2) played a minor role in the degradation process. This study elucidates the detailed mechanism of PDS activation by Fe-CB, resulting in the generation of reactive oxygen species. It highlights the effectiveness of Fe-CB/PDS in a Fenton-like system for the treatment of water polluted with organic dye contaminants. The research provides valuable insights into the potential application of carbon black derived from tire waste for environmental remediation.

Heavy metal pollution in the aquatic environment: efficient and low-cost removal approaches to eliminate their toxicity: a review.

Heavy metal contamination of water sources has emerged as a major global environmental concern, threatening both aquatic ecosystems and human health. Heavy metal pollution in the aquatic environment is on the rise due to industrialization, climate change, and urbanization. Sources of pollution include mining waste, landfill leachates, municipal and industrial wastewater, urban runoff, and natural phenomena such as volcanic eruptions, weathering, and rock abrasion. Heavy metal ions are toxic, potentially carcinogenic, and can bioaccumulate in biological systems. Heavy metals can cause harm to various organs, including the neurological system, liver, lungs, kidneys, stomach, skin, and reproductive systems, even at low exposure levels. Efforts to find efficient methods to remove heavy metals from wastewater have increased in recent years. Although some approaches can effectively remove heavy metal contaminants, their high preparation and usage costs may limit their practical applications. Many review articles have been published on the toxicity and treatment methods for removing heavy metals from wastewater. This review focuses on the main sources of heavy metal pollution, their biological and chemical transformation, toxicological impacts on the environment, and harmful effects on the ecosystem. It also examines recent advances in cost-effective and efficient techniques for removing heavy metals from wastewater, such as physicochemical adsorption using biochar and natural zeolite ion exchangers, as well as decomposition of heavy metal complexes through advanced oxidation processes (AOPs). Finally, the advantages, practical applications, and future potential of these techniques are discussed, along with any challenges and limitations that must be considered.

Heterogeneous catalytic activation of peroxydisulfate toward degradation of pharmaceuticals diclofenac and ibuprofen using scrap printed circuit board.

Pharmaceutical residues have been identified as a priority contaminant due to their toxicity to organisms and the ecosystem as representative refractory organic compounds in water. Therefore, using efficient treatment methods to remove them from wastewater has become a crucial topic of research. Advanced oxidation processes (AOPs) based on the sulfate radical have gained increased attention in recent years due to their superior performance and adaptability in the decomposition of refractory organic contaminants. In this work, scrap printed circuit boards (PCBs) were used to prepare a low-cost and efficient heterogeneous peroxydisulfate (PDS) catalytic activator via thermal treatment with an air combustion non-carbonized catalyst (NCC) and pyrolysis with a nitrogen carbonized catalyst (CC) for the removal of diclofenac (DCF) and ibuprofen (IBF) from water at circumneutral pH. The synthesized catalysts were characterized by several analytical techniques. The effects of various experimental parameters on the removal efficiency were examined. Under optimum conditions, the degradation efficiency reached 76% and 71% with NCC and 63% and 57.5% with CC within 60 min for DCF and IBP, respectively. The mineralization efficiency as measured by TOC removal reached up to 65% after 60 min treatment. The degradation kinetics for both catalysts followed the pseudo-first-order model. Results from quenching tests showed that the reactive oxidizing species (ROS), including 1O2 > SO4˙- > ˙OH, were generated mainly in the NCC/PDS and CC/PDS systems. Overall, the prepared catalysts were found to be effective and reusable for PDS activation for the removal of pharmaceutical pollutants from water. This study provided a promising, robust and efficient heterogeneous catalytic PDS activation based on the strategy of "waste-treats-waste" for the removal of pharmaceutical pollutants from water.

Application of different advanced oxidation processes for the removal of chloroacetic acids using a planar falling film reactor.

Advanced oxidation processes (AOPs) are considered as an effective and promising method for the degradation and mineralization of aqueous recalcitrant organic pollutants. In this study, application of ozonation and various types of AOPs including photocatalysis, Fenton alone and their combinations were investigated and compared for the degradation and mineralization of chloroacetic acids (CAAs) in aqueous solutions, using a planar falling film reactor. CAAs are widely available in water treated by chlorination processes and are resistance against ozonation in the darkness. The results of the present work showed that the plain ozonation was inefficient method for the destruction of the CAAs as only about 2% degradation was observed after 90 min treatment. However, the best results were achieved by ozone in combinations with other oxidation processes. Furthermore, a synergistic effect on the removal rate was observed when these processes were exposed to the UVA light. Among the examined processes, combination of photo-Fenton with ozonation was found to be the fastest one for CAAs degradation. The effects of different parameters such as initial concentration of Fe2⁺, H2O2 and CAAs in photo-Fenton combined with ozonation were investigated. The optimum ratio of 0.12 of Fe2⁺/H2O2 concentration was found to give the best result for CAAs degradation. The degree of CAAs mineralization, measured by the total organic carbon removal, as well as the effect of falling liquid film flow rate on the removal of CAAs were also studied and discussed.

Comparative study on 2,4-dichlorophenoxyacetic acid and 2,4-dichlorophenol removal from aqueous solutions via ozonation, photocatalysis and non-thermal plasma using a planar falling film reactor.

Ozonation and advanced oxidation processes based on photocatalysis (P.C.) and non-thermal plasma generated in a dielectric barrier discharge (DBD) in different gas atmospheres were compared for the degradation and mineralization of 2,4-dichlorophenoxy acetic acid (2,4-D) and 2,4-dichlorophenol (2,4-DCP) in aqueous solutions, using a planar falling film reactor with comparable design. The energetic yields (G50) as measure of the efficiencies of the different methods are for 2,4-D in the order DBD/Ar-Fenton>ozonation>DBD/Ar>P.C.ozonation>DBD/Ar:O2≫DBD/Air>P.C.oxidation. For 2,4-DCP the order is ozonation≫DBD/Ar-Fenton>P.C.ozonation>DBD/Ar>DBD/Ar:O2≫P.C.oxidation>DBD/Air. The degradation by using ozone is very effective, but it should be noted that the mineralization measured by the total organic carbon (TOC) removal is low. The reason is the formation of stable towards ozone intermediates, especially low chain carboxylic acids. The fate of these intermediates during the degradation with the different methods has been followed and discussed.