# Isoconversional Kinetic Analysis and ANN-Based Prediction of Metformin Pyrolysis for Sustainable Waste Management

## TL;DR

This study explores pyrolysis as a sustainable method to manage pharmaceutical waste by recovering valuable compounds from metformin.

## Contribution

The study introduces an ANN-based prediction model for metformin pyrolysis and evaluates its potential for pharmaceutical waste valorization.

## Key findings

- Pyrolysis of metformin produced liquid-phase products containing the active pharmaceutical ingredient and other compounds.
- An ANN model accurately predicted mass loss during pyrolysis using temperature and heating rate as inputs.
- Recovered APIs and byproducts could be reused for energy or chemical synthesis, supporting circular economy goals.

## Abstract

Pharmaceutical waste poses a growing environmental concern
due
to its persistence and potential ecological impacts, necessitating
effective and sustainable management strategies. This study investigates
the pyrolysis of metformin as a means to valorize pharmaceutical waste
within a circular economy framework. Pyrolysis experiments conducted
on 500 mg of metformin demonstrated the formation of liquid-phase
products, characterized by GC–MS, which revealed a high concentration
of the active pharmaceutical ingredient (API) alongside carbonaceous,
nitro, and acidic compounds. Comprehensive thermogravimetric analyses
at heating rates of 10, 20, 30, and 40 °C/min were performed
to evaluate the thermal decomposition behavior. Kinetic parameters
were determined using four isoconversional methods, namely KAS, FWO,
Starink, and FRD, yielding average activation energies of 101.4, 105.8,
101.4, and 111.1 kJ/mol, respectively. Thermodynamic parameters (ΔG, ΔH, and ΔS) were also calculated to gain further insights into the decomposition
process. Additionally, an ANN model was developed using temperature
and heating rate as inputs to predict mass loss, achieving accurate
estimations with an optimized architecture comprising two hidden layers.
GC–MS analysis of the pyrolysis liquid identified a high concentration
of the API, along with carbonaceous, nitro, and acidic compounds.
These findings highlight the potential for API recovery and reuse,
as well as the valorization of byproducts for energy or chemical synthesis.
The potential recovery of APIs for reuse and the utilization of byproducts
as fuels or chemical precursors underscore pyrolysis as a promising
route for sustainable pharmaceutical waste management and circular
economy integration.