Norfloxacin adsorption on montmorillonite and carbon/montmorillonite hybrids: pH effects on the adsorption mechanism, and column assays

A Unified Adsorption Kinetic Model Inspired by Epidemiological Model: Based on Adsorbates "Infect" Adsorbents

Adsorption is a unit operation used in various fields, including the environmental, chemical, and pharmaceutical industries. Understanding the adsorption kinetics is crucial to designing efficient adsorption systems. However, existing empirical adsorption models are limited in providing insights into the mass transfer mechanisms. Additionally, the absence of a unified adsorption kinetic model hampers the effective comparison of different adsorption systems. Here, we viewed the adsorption as an "infectious process of adsorbates by adsorbents" akin to epidemiology. In epidemiology, individuals can be divided into susceptible, infected, and recovered compartments, ignoring the complexities of movement among individuals. Analogously, we have categorized the adsorbates as adsorbable, adsorbed, and removed compartments. Thus, we proposed a unified adsorption kinetic model (the monolayer-multilayer-adsorbable-adsorbed-removed model) that accommodates monolayer/multilayer adsorption. The model was designed to encompass diverse adsorption setups, including continuous and batch processes with fixed/dispersed adsorbents. The versatility and applicability of the model were demonstrated through validation using a diverse set of experimental data. This validation underscored its effectiveness in water/wastewater treatment, salt reduction, metal recovery, and drug purification. A MATLAB-based program for solving this model was made available to researchers for their utilization and further investigations. Overall, this study developed a versatile adsorption kinetic model that offers a comprehensive and unified understanding of adsorption kinetics across various applications.

Adsorption of norfloxacin from wastewater by biochar with different substrates

The type of feedstock and pyrolysis temperature are the main reasons affecting the properties of the resulting biochar. Therefore, this paper investigates the effects of different feedstocks (peanut shell, corn straw and soybean straw) and different pyrolysis temperatures (300, 450 and 600 ℃) on the structural morphology and elemental composition of the resulting biochar. The optimum pyrolysis temperature of 600 ℃ was selected based on the comparison of the adsorption of NFX (norfloxacin) by the biochar prepared at different temperatures. Characterization of biochar materials using x-ray diffractometer, fourier transform infrared spectrometer and scanning electron microscope to study the changes in the physicochemical and structural properties of biochar. The results showed that the pH, surface area and ash content of biochar are increased with increasing temperature. The results of isothermal adsorption and adsorption kinetics experiments showed that the adsorption processes of the three biochar species on NFX were consistent with the Langmuir model and Pseudo-second order kinetic model. The adsorption process occurred in the surface layer of the biochar and was dominated by chemisorption. The inhibition of the adsorption of NFX was more obvious with the higher valence state of cations and the higher ion concentration. The adsorption mechanism of biochar on NFX includes pore filling, hydrogen bonding and electrostatic interactions.

A review of the adsorption method for norfloxacin reduction from aqueous media

Norfloxacin (NRFX) is one of a class of antibiotics known as broad-spectrum fluoroquinolone antibiotic that is frequently used to treat infectious disorders in both animals and humans. NRFX is considered an emergent pharmaceutical contaminate. This review's objective is to evaluate empirical data on NRFX's removal from aqueous medium. The environmental danger of NRFX in the aquatic environment was validated by an initial ecotoxicological study. Graphene oxide/Metal Organic Framework (MOF) based composite, followed by Magnesium oxide/Chitosan/Graphene oxide composite gave the highest NRFX adsorption capacities (Qmax) of 1114.8 and 1000 mg/g, respectively. The main adsorption mechanisms for NRFX uptake include electrostatic interactions, H-bonds, π-π interactions, electron donor-acceptor interactions, hydrophobic interactions, and pore diffusion. The adsorptive uptake of NRFX were most suitably described by Langmuir isotherm and pseudo-second order implying adsorbate-to-adsorbent electron transfer on a monolayer surface. The thermodynamics of NRFX uptake is heavily dependent on the makeup of the adsorbent, and the selection of the eluent for desorption from the solid phase is equally important. There were detected knowledge gaps in column studies and adsorbent disposal method. There's great interest in scale-up and industrial applications of research results that will aid in management of water resources for sustainability.

Antibiotic adsorption by natural and modified clay minerals as designer adsorbents for wastewater treatment: A comprehensive review

Increased antibiotic use worldwide has become a major concern because of their health and environmental impacts. Since most antibiotic residues can hardly be removed from wastewater using conventional treatments, alternative methods receive great attention. Adsorption is one of the most efficient and cost-effective treatment methods for antibiotics. Among the adsorbents, clay minerals have garnered increasing attention due to their unique properties including availability, high specific surface area, low cost, cation exchange capacity, and good removal efficiency. This paper reviews the recent progress made in the use of natural and modified clay minerals for the removal of antibiotics from water. First, the sources, occurrence, removal and health effects of the antibiotics commonly encountered in water bodies are described. Antibiotic concentration levels and average removal efficiencies measured in conventional activated sludge treatment systems worldwide are also provided to better address the problem. Second, the review explores the characteristics of clay minerals as adsorbent of antibiotics and the factors affecting the adsorption. The review identifies and discusses the future trends and strategies used to increase the adsorption capacity of clay minerals by modification and combination techniques (intercalation of novel functional groups such as organocations, biopolymers and metal pillared-clay minerals, combination with biochar or thermal activation). The quantitative comparisons of clay minerals' ability for antibiotic removal are given. Some natural clay minerals have good removal potential for antibiotics, with maximum adsorption capacities over 100 mg/g. For most other adsorbents, surface modifications and combination techniques resulted in improved adsorption properties (including higher surface area, enhanced adsorption capacity, increased stability and mechanical strength). Finally, the application of these adsorbents at pilot scale, using real wastewater samples, their reuse, economic analysis and life cycle assessment are other issues that have been considered.

Batch and Column Adsorption of Phosphorus by Modified Montmorillonite

Phosphorus pollutants are a crucial component of water eutrophication. In this study, montmorillonite modified by Keggin Al13 and hexadecyltrimethyl ammonium (Al13-O-MMt) was used as an adsorbent to remove phosphorus from solutions and thus simulate the practice of a field trial, such as in wastewater. The ammonium molybdate spectrophotometric method was used to determine the concentrations of phosphorus in samples. In the batch experiment, phosphorus was adsorbed by original montmorillonite (MMt) and Al13-O-MMt at various pH values (6–9) to identify the effect of pH during the adsorption process. The batch adsorption results demonstrate that Al13-O-MMt can adsorb up to 93% of phosphorus at pH = 8. Six graduated amounts (0.01–0.25 g) of montmorillonite were tested at three different temperatures to determine the most suitable temperature and the minimum dosage of Al13-O-MMt needed for the adsorption of 200 mg/L phosphorus in a 30 mL solution, which was 0.1 g at 25 °C. Therefore, the adsorption capacity of Al13-O-MMt was found to be 60 mg/g. Subsequently, a column experiment was conducted. The results showed that the optimized dosage of Al13-O-MMt was 6.667 g for phosphorus adsorption with a concentration of 200 mg/L in 2000 mL solution, and the breakthrough time was 4794.67 min.