# Unveiling the Challenge of Evaporator Design in Clean Water Production Promoted by Superabsorbent Hydrogels and Sunlight

## TL;DR

A new hydrogel material is developed to efficiently produce clean water using sunlight and seawater, even in drought-prone areas like the Mediterranean.

## Contribution

A thermoresponsive hydrogel with solar absorber properties is introduced for enhanced clean water production.

## Key findings

- The hydrogel achieves an evaporation rate of 6.34 kg·m–2·h–1 using sunlight and a low amount of photothermal material.
- The material shows strong removal of cations and transition metals and maintains performance through multiple cycles.
- The design minimizes heat loss and outperforms other solar vapor generator architectures.

## Abstract

Climate change is affecting water availability and the
supply.
This situation is particularly worrying in Mediterranean area countries,
where droughts are becoming increasingly long and severe. Herein,
a superabsorbent porous hydrogel composed of thermoresponsive hydrogel
(TSH) poly­(N-isopropylacrylamide) (PNIPAAm), copolymerized
with poly­(acrylamide) (PAAm) and modified with poly­(3,4-ethylenedioxythiophene)
polystyrenesulfonate (PEDOT/PSS), as a solar absorber, is presented.
This superabsorbent hydrogel optimizes water uptake and provides long
life stability through a continuous supply of water to the evaporation
surface, promoted by its thermosensitivity property and light absorption
efficiency with a very low amount of photothermal material (1 wt %).
The fine-tuning of both the hydrogel composition and the solar vapor
generator (SVG), assisted by a metallic reflector, results in an impressive
evaporation rate (ER) of 6.34 kg·m–2·h–1. This configuration minimizes the heat losses and
allows maintaining the ER high, if compared to other SVG architectures.
The hydrogel also exhibits strong removal capacity for monovalent
cations and transition metals as well as reusability properties under
stable multiple evaporation-swelling cycles, thanks to its good covalent
interpenetrating network and its mechanical integrity. This superlative
performance significantly expands the potential applications of porous
hydrogels in clean water production, which are moved by sunlight irradiation
and seawater, two abundant natural resources.