MOF‐Heterostructure‐Mediated pH‐Responsive Adsorptive Removal of Ciprofloxacin: A Step towards Pharmaceutical Wastewater Treatment

Abstract

One of the biggest challenges of the modern world is the antibiotic pollution in the water resources owing to the lack of effective removal techniques in the conventional wastewater treatment processes. Importantly, very few commercially available adsorbents are at the same time porous, magnetic, and have the capacity to bind and remove particular antibiotic classes from the slurries in a selective manner. Herein we report CNS@ZIF67 heterostructure derived adsorbent for the pH‐dependent removal of ciprofloxacin (CIP). The materials can be synthesized via a simple two‐step wet chemical method followed by annealing in a controlled atmosphere. The material demonstrates an attractive surface‐to‐mass ratio of 203.02 m2 g−1. We have performed a detailed time dependent adsorption study indicating a high removal efficiency of 96% within 2 h. Experimental adsorption data matches the Langmuir isotherm model and the kinetics follows pseudo‐second‐order reaction kinetics suggesting a chemisorption pathway of adsorption kinetics. The adsorbent has an interesting pH dependent adsorption behavior towards CIP. The adsorbent has also demonstrated its value in being reusable for four cycles of adsorption and desorption without significantly changing the removal efficiency.

Ciprofloxacin adsorption performance of Co‐doped UiO‐66

“…The pH pzc (pH at the point of zero charge) of the Co‐doped UiO‐66 was determined as 2.3 (Figure 4b), indicating the Co‐doped UiO‐66 with negatively charged surface at pH values higher than 2.3 40 . The maximum ciprofloxacin removal percentage at pH 5 can be explained with electrostatic interactions between the ciprofloxacin molecules in cationic form and Co‐doped UiO‐66 with negative surface charge 41 . However, anionic ciprofloxacin molecules and negatively charged Co‐doped UiO‐66 repel each other at high pH values, which reduces the ciprofloxacin removal percentage 42 .…”

pH-dependent adsorption of the sulfamethoxazole antibiotic on HKUST-1@CNS nanocomposite corroborating efficiency, mechanistic, and kinetic studies

“…A kinetic model describes the underlying driving force and characteristics of the adsorption process. 62 We have fitted the adsorption data to the first-order and second-order kinetic models. Following are the descriptions of the pseudo-firstorder and pseudo-second-order models:…”

“…This leads to strong repulsion between the molecules of CIP and HKUST-1, leading to its lowest adsorption on the HKUST-1@CNS adsorbent. 62,68 The NAL molecule exists as an anionic species above pH 5.95. Therefore, the aromatic rings in the NAL molecules and the p-electron network of the graphitic carbon present in the HKUST-1@CNS adsorbent were primarily responsible for the p-p interactions, which influence the adsorption of NAL at higher pH leading to its 71.10% removal.…”

Nitrogen‐Doped Graphene Nanosheets for Sustainable Removal of Pharmaceutical Contaminants from Water: Kinetics and ANFIS Modeling

“…To develop such an eco-friendly, cost-effective, reusable and efficient technique, adsorption is the first feasible preference owing to its efficiency, simple and easy operation, low-cost and potential recovery of contaminants without any intermediate product. [24][25][26][27] This method does not produce any new by-product, which is a noteworthy advantage over other processes. [18,28,29] In the last few decades, different carbon-based adsorbents such as graphene oxide (GO), carbon nanotubes (CNTs), activated carbon (AC), and biochar have been explored by various researchers as an effective strategy to remove organic contaminants from aqueous matrices.…”

“…Thus, a self‐sustainable, safe, robust, and economical wastewater treatment method is the utmost concern of the environmental technologists for the compounds of interest to be treated with minimal toxic by‐products formation. To develop such an eco‐friendly, cost‐effective, reusable and efficient technique, adsorption is the first feasible preference owing to its efficiency, simple and easy operation, low‐cost and potential recovery of contaminants without any intermediate product [24–27] . This method does not produce any new by‐product, which is a noteworthy advantage over other processes [18,28,29] …”