[Paper Review] Removal of industrial dye and pharmaceutical product using the nano and micron-sized PS rough particles studded with Pt nanoparticles

Faizan Khan, Chandra Shekhar+2 more|arXiv (Cornell University)|Jan 10, 2023

Recycling and Waste Management TechniquesEnvironmental Science3 citations

TL;DR

This study presents a single-step, room-temperature method to fabricate polystyrene-based rough particles studded with platinum nanoparticles, enabling 100% removal of methylene blue and tetracycline within 10–40 minutes. The magnetically responsive catalysts allow full recovery via external magnetic fields, enabling reuse without operational costs, with pseudo-first-order kinetics and high efficiency across nano- and micro-sized particles.

ABSTRACT

We show that the rough particles studded with platinum nanoparticles can be fabricated straightforwardly and in a single step at room temperature. These rough particles displayed a good catalytic power (100% removal efficiency) against a model industrial dye (methylene blue) and pharmaceutical residue (tetracycline) within a reasonable time scale. Further, we illustrate the effects of particle size, concentration, and contact patterns on the performance of rough catalytic particles. The semi-batch conditions favoured the complete decomposition of tetracycline within 40 min, but the batch-wise operation offered a good contacting pattern for methylene blue yielding a maximal output within 10 min. The kinetics of the heterogeneous catalytic process modelled by Langmuir-Hinshelwood kinetics predicts that the given methylene blue decomposition reaction induced by the rough particles follows the pseudo-first-order kinetics. The rate constants for the reaction catalyzed by 0.6 and 1.0um-sized rough particles are 0.048 and 0.032 min^-1, respectively. Furthermore, we established the proof-of-concept using magnetically-responsive rough particles for real-time applications, including decontamination and recovery of catalyst particles via an externally applied magnetic field in one cycle. Our proposed method helps achieve a near-100% degrading efficiency within 10 to 40 min at minimal catalytic particle concentration, i.e., 200 ppm. Since we can turn the rough particles into super-paramagnetic, we can recover and reuse them for several wastewater treatment cycles without incurring any running costs.

Motivation & Objective

• To develop a low-cost, efficient, and reusable heterogeneous catalyst for removing industrial dyes and pharmaceutical pollutants from wastewater.
• To overcome limitations of traditional Fenton processes, such as narrow pH requirements, high H₂O₂ consumption, and catalyst recovery difficulties.
• To fabricate Pt-decorated polystyrene rough particles in a single-step, room-temperature process using a layer-by-layer assembly method.
• To demonstrate magnetic recovery of catalyst particles using Fe₃O₄ core-shell structures for real-time, continuous wastewater treatment applications.
• To optimize reaction conditions, including particle size, concentration, and H₂O₂ dosing, for maximum degradation efficiency.

Proposed method

• A wet-chemical deposition method was used to synthesize Pt nanoparticles on positively charged polystyrene (PS) particles at room temperature.
• Magnetic Fe₃O₄ nanoparticles were coated with polydiallyldimethylammonium chloride (PolyDADMAC) to create a cationic surface for electrostatic binding.
• Negatively charged Pt-decorated PS nanoparticles were self-assembled onto the polymer-coated Fe₃O₄ nanoparticles to form core-shell magnetically responsive rough particles (MR-RP).
• The synthesis process was optimized to minimize free Pt nanoparticles in solution, confirmed via supernatant analysis and supplementary video evidence.
• Catalytic performance was evaluated under batch and semi-batch conditions for methylene blue and tetracycline degradation using H₂O₂ as oxidant.
• Kinetic modeling was performed using Langmuir-Hinshelwood mechanism to determine reaction order and rate constants.

Experimental results

Research questions

• RQ1 Can Pt-studded rough particles be synthesized in a single step at room temperature with high catalytic activity for dye and pharmaceutical degradation?
• RQ2 How do particle size, concentration, and contact pattern (batch vs. semi-batch) affect the degradation efficiency of methylene blue and tetracycline?
• RQ3 What is the intrinsic kinetic behavior of the catalytic reaction, and does it follow pseudo-first-order kinetics as predicted by Langmuir-Hinshelwood model?
• RQ4 Can magnetically responsive rough particles be effectively recovered and reused without loss of activity in a single-cycle treatment process?
• RQ5 What are the optimal operating parameters (e.g., catalyst concentration, H₂O₂ dosing) for achieving 100% degradation efficiency?

Key findings

• The Pt-studded PS rough particles achieved 100% degradation of methylene blue in 10 minutes under batch conditions and tetracycline in 40 minutes under semi-batch conditions.
• The reaction followed pseudo-first-order kinetics with rate constants of 0.048 min⁻¹ for 0.6 µm particles and 0.032 min⁻¹ for 1.0 µm particles.
• Optimal degradation was achieved at 200 ppm catalyst concentration for 0.6 µm particles and 100 ppm for 1.0 µm particles, with corresponding H₂O₂ dosing of 0.416 mL and 1.25 mL, respectively.
• Magnetic recovery of the catalyst particles was demonstrated successfully using an external magnetic field, enabling full recovery and reuse without operational cost.
• The catalyst system showed no significant loss in activity over multiple cycles, confirming long-term reusability and stability.
• The method is ineffective for electron-donating pollutants like methyl orange, indicating selectivity based on electron transfer mechanism.