Waste glass from end-of-life fluorescent lamps as raw material in geopolymers

Nowadays the stunning volume of generated wastes, the exhaustion of raw materials, and the disturbing greenhouse gases emission levels show that a paradigm shift is mandatory. In this context, the possibility of using wastes instead of virgin raw materials can mitigate the environmental problems related to wastes, while reducing the consumption of the Earth’s natural resources. This innovative work reports the incorporation of unexplored waste glass coming from end-of-life fluorescent lamps into geopolymers. The influence of the waste glass incorporation level, NaOH molarity and curing conditions on the microstructure, physical and mechanical properties of the geopolymers was evaluated. Results demonstrate that curing conditions are the most influential factor on the geopolymer characteristics, while the NaOH molarity is less important. Geopolymers containing 37.5% (wt) waste glass were successfully produced, showing compressive strength of 14 MPa (after 28 days of curing), suggesting the possibility of their use in non-structural applications. Porous waste-based geopolymers for novel applications were also fabricated

Examination of Photocatalyzed Chlorophenols for Sequential Photocatalytic-Biological Treatment Optimization

Given the known adverse effect of chlorophenols for the aquatic environments which they can reach, the development of efficient methods both technically and economically to remove them has gained increasing attention over time. The combination of photocatalytic oxidation with biological treatment can lead to high removal efficiencies of chlorophenols, while reducing the costs associated with the need to treat large volumes of aqueous solutions. Therefore, the present paper had as its main objective the identification of the minimum photocatalytic oxidation period during which the aqueous solutions of 4-chlorophenol and 2,4-dichlorophenol can be considered as readily biodegradable. Thus, the results of photocatalytic oxidation and biodegradability tests showed that, regardless of the concentration of chlorophenol and its type, the working solutions become readily biodegradable after up to 120 min of irradiation in ultraviolet light. At this irradiation time, the maximum organic content of the aqueous solution is less than 40%, and the biochemical oxygen demand and chemical oxygen demand (BOD/COD) ratio is much higher than 0.4. The maximum specific heterotrophic growth rate of activated sludge has an average value of 4.221 d−1 for 4-chlorophenol, and 3.126 d−1 for 2,4-dichlorophenol. This irradiation period represents at most half of the total irradiation period necessary for the complete mineralization of the working solutions. The results obtained were correlated with the intermediates identified during the photocatalytic oxidation. It seems that, working solutions initially containing 4-chlorophenol can more easily form readily biodegradable intermediates

Influence of Operating Parameters on Photocatalytic Oxidation of 2,4-Dichlorofenol in Aqueous Solution by TiO2/Stainless Steel Photocatalytic Membrane

The influence of some operating parameters of an UV photocatalytic reactor with TiO2/stainless steel photocatalytic membrane on the photocatalytic oxidation of 2,4-dichlorophenol from aqueous solutions was studied in this paper. It was shown that the pH of the working solution substantially influences the photocatalytic degradation of the organic substrate, with the degradation efficiency increasing with decreasing the pH of the working solution by a maximum corresponding to pH 3. The rate constant of the photocatalytic oxidation process is about twice as high at pH 3 comparative with pH 7 for the same initial concentration of the organic substrate. The molar ratio of hydrogen peroxide/organic substrate also influences the photocatalytic oxidation process of the organic substrate. The results obtained in this paper highlight the fact that a stoichiometric molar ratio is favorable for the photocatalytic degradation of 2,4-dichlorophenol. It has also been shown that the initial concentration of the organic substrate influences the rate of photocatalytic degradation. It appears that the rate of photocatalytic degradation decreases with the increasing of initial concentration of 2,4-dichlorophenol

Influence of Operating Parameters on Photocatalytic Oxidation of 2,4-Dichlorofenol in Aqueous Solution by TiO₂/Stainless Steel Photocatalytic Membrane

The influence of some operating parameters of an UV photocatalytic reactor with TiO2/stainless steel photocatalytic membrane on the photocatalytic oxidation of 2,4-dichlorophenol from aqueous solutions was studied in this paper. It was shown that the pH of the working solution substantially influences the photocatalytic degradation of the organic substrate, with the degradation efficiency increasing with decreasing the pH of the working solution by a maximum corresponding to pH 3. The rate constant of the photocatalytic oxidation process is about twice as high at pH 3 comparative with pH 7 for the same initial concentration of the organic substrate. The molar ratio of hydrogen peroxide/organic substrate also influences the photocatalytic oxidation process of the organic substrate. The results obtained in this paper highlight the fact that a stoichiometric molar ratio is favorable for the photocatalytic degradation of 2,4-dichlorophenol. It has also been shown that the initial concentration of the organic substrate influences the rate of photocatalytic degradation. It appears that the rate of photocatalytic degradation decreases with the increasing of initial concentration of 2,4-dichlorophenol

Key Principles of Advanced Oxidation Processes: A Systematic Analysis of Current and Future Perspectives of the Removal of Antibiotics from Wastewater

In line with the development of industrial society, wastewater has caused multiple environmental problems. Contaminants of emerging concern (CECs) in water and wastewater are persistent, and for this reason they can cause serious problems for human health, animal health, and the whole environment. Therefore, it is absolutely necessary to apply efficient methods for the treatment of wastewater that has a high concentration of organic compounds. Over recent years, the prescribed and non-prescribed consumption of antibiotics has increased significantly worldwide. Large quantities of antibiotics are discharged into wastewater because of their incomplete absorption by living organisms. However, even small concentrations present in aquatic environments represent a major risk to human health and environment protection. This paper presents the main advantages and disadvantages of advanced oxidation processes, and the current state and new perspectives in the field of environment protection. This study summarizes data from the most recent specialized scientific literature that focuses on the topic of advanced oxidation processes, thus bringing all these aspects to the attention of researchers in a single work that adds comments and interpretations related to the presented processes. Advanced oxidation processes (AOPs) are often used in the treatment of different types of wastewater. AOPs are based on physicochemical processes that create significant structural changes in chemical species. The majority of antibiotics may be eliminated using physicochemical processes, such as photo-Fenton oxidation, photolysis, ozonation, electrooxidation, heterogeneous catalysis, and other bioprocesses. In comparison to conventional chemical processes, AOPs provide superior oxidation efficiency, ideal operating costs, and zero secondary pollutants

Photocatalytic Degradation of Ampicillin Using PLA/TiO2 Hybrid Nanofibers Coated on Different Types of Fiberglass

New photocatalytic membranes based on polylactic acid (PLA)/TiO2 hybrid nanofibers deposited on fiberglass supports were prepared and tested for the removal of ampicillin from aqueous solutions. The electrospinning technique was used to obtain hybrid nanofibers that were deposited on three types of fiberglass with different structures, resulting in three distinct photocatalytic membranes namely fiberglass fabric plain woven-type membrane, fiberglass mat-type membrane, and fiberglass fabric one-fold edge-type membrane. The results of the photocatalytic tests showed that the highest efficiency of ampicillin removal from aqueous solution is obtained with the fiberglass fabric plain woven-type membrane. Although it has been shown that the rate of photocatalytic degradation of ampicillin is high, being practically eliminated within the first 30 min of photocatalysis, the degree of mineralization of the aqueous solution is low even after two hours of photocatalysis due to the degradation of PLA from the photocatalytic membrane. The instability of PLA in the reactive environment of the photocatalytic reactor, evidenced by morphological, mineralogical and spectroscopic analyzes as well as by kinetic studies, is closely related to the structure of the fiberglass membrane used as a support for PLA/TiO2 hybrid nanofibers

Synthesis, Characterization and Sorption Capacity Examination for a Novel Hydrogel Composite Based on Gellan Gum and Graphene Oxide (GG/GO)

A novel hydrogel composite based on gellan gum and graphene oxide (GG/GO) was synthesized, characterized and tested for sorption capacity in this work. The microstructural, thermogravimetric and spectroscopic analysis confirmed the formation of the GG/GO composite. Comparative batch sorption experiments revealed a sorption capacity of the GG/GO composite for Zn (II) ions of approximately 2.3 higher than that of pure GG. The GG/GO composite exhibits a maximum sorption capacity of 272.57 mg/g at a pH of Zn (II) initial solution of 6. Generally, the sorption capacity of the sorbents is approximately 1.5 higher in slightly acidic conditions (pH 6) comparative with that for strong acidic conditions (pH 3). The sorption isotherms revealed that the sorption followed a monolayer/homogenous behavior. The sorption kinetic data were well fitted by the pseudo-second-order kinetic model, and were consistent with those derived from sorption isotherms. The intraparticle diffusion was considered to be the rate-determining step. Two main sorption mechanisms for Zn (II) were identified namely, ion exchange at low pH values, and both ion exchange and chemisorption in weekly acidic conditions