**7. Conclusions**

Pollution from mining and industry continues to be serious environmental problem in Xiangjiang Valley, which is the key rice production area in Hunan province. We need to identify approaches to deal with the protection of the food chain over widespread areas. Adsorption is still an effective technology for removing metals from water, but requires careful consideration to deal with multiple metals, sources, and regional scale contamination. In this review, sepiolite based materials were selected as target adsorbents for heavy metals removal because of their local abundance and potential cost effective application. The characteristics and function of natural and modified sepiolites are reviewed and compared. The sorption performance of modified sepiolite obtained from acid, magnetic, organic, and thermal treatment is significantly improved over natural materials and can be re-used through regeneration. These methods include acid, alkaline, and salt regeneration. The sorption performance of sepiolite after regeneration is greater than 70% of its original performance.

We identified that the relatively low efficiency for heavy metal removal by natural sepiolite was because of the scarcity of exchange sites for contaminant metal ions and capacities are much lower than other synthetic sorbent materials. However, the modification of sepiolite is viable and provides potentially useful adsorption capacity. However, the process of modification also increases the cost of any potential application. In our review, few reports have considered the cost–benefit for modification of sepiolite and application of modified sepiolite on removing metals. Most studies still focus on the mechanism of modification and regeneration of sepiolite. In order to fully establish the potential of sepiolite, as a low-cost and effective adsorbent, further field scale research involving a product life cycle approach is required. This will identify the full potential of local resources to treat local pollution and meet with recent national (China) international (EU–China) agreements on resource conservation and environmental protection.

**Author Contributions:** Drafting the manuscript, Z.W. & L.L.; Data collection, Z.W., L.L., & N.S.; Critical review, Z.W., & A.H.; Writing–review & editing, A.H., Z.W., & B.R.; Funding Acquisition, A.H.; All authors have given approval of the version to be published.

**Funding:** This research was part funded by the Hunan Provincial Hundred Talents Program.

**Acknowledgments:** Zhenghua Wang was supported by the China Scholarship Council for one year study at the University of the West of Scotland.

**Conflicts of Interest:** The authors declare no conflict of interest.
