Increasing arsenic sorption on red mud by phosphogypsum addition

► This study investigates As sorption on by-products from Brazil. ► Red mud has been studied as a good adsorbent for arsenic. ► Phosphogypsum mixed with red mud increases arsenic retention capacity. ► The mixture provides S and Ca for plant growth during revegetation. ► The mixture constitutes an amendment to be tested in arsenic-contaminated soil.