# Enhancing Restoration of Arid Mining Area Using Lignite-Based Superabsorbent Gel

## TL;DR

A new superabsorbent gel made from lignite helps restore dry mining areas by retaining water and improving plant growth.

## Contribution

A lignite-based superabsorbent gel is developed for ecological restoration in arid mining areas with high water retention and reusability.

## Key findings

- The gel achieved 522 g·g−1 water absorption in distilled water and 65.5 g·g−1 in salt solution.
- The gel retained over 81.8% of its water absorption capacity after five reuse cycles.
- Field trials showed improved vegetation coverage in mining areas using the gel.

## Abstract

This research designed a high-performance superabsorbent gel aligned on the integration of lignite humic residue (LHR) with a polymeric organic network in order to address ecological restoration challenges in the arid mining area in Xinjiang. This water-retaining agent was synthesized by employing solution polymerization techniques using acrylic acid (AA) and acrylamide (AM) as monomers, lignite hydrothermal residue (LHR) as a functional additive, and ammonium persulphate (APS) as the initiator. The resulting lignite hydrothermal residue–polyacrylic gel composite material was obtained by using N,N′-methylene-bisacrylamide (MBA) as the primary crosslinking agent. The water absorption capacity and mechanical strength of the acrylic gel were further enhanced by specifically incorporating low-cost, safe, and non-toxic lignite humic residue (LHR). The performance test indicated that this gel achieved a maximum water absorption of 522 g·g−1 in distilled water and 65.5 g·g−1 in 0.9% sodium chloride solution. Its reusability and water absorption capacity remained above 81.8% even after five cycles of natural dehydration and reabsorption. The method for synthesizing this superabsorbent gel effectively constructs a soil water retention network structure, improving the soil microenvironment, and enhancing plant salt tolerance. The field trial results showed that the application of this LHR-AA-AM superabsorbent gel considerably improved vegetation coverage in mining areas. Hence, this study provides an efficient and economical superabsorbent material for ecological restoration of saline–alkali land in arid regions without soil replacement, demonstrating promising application prospects.