Evaluation of a cactus mucilage biocomposite to remove total arsenic from water

• New approach of cactus mucilage from Opuntia ficus-indica for As removal.
• Encapsulation of cactus mucilage in alginate beads as a new eco-friendly adsorbent.
• Biomaterial formulation was evaluated using Box–Behnken experimental design.
• Gelling fraction of mucilage has demonstrated great potential for As removal (63%).
• Enhanced separation of mucilage-As complex from wastewater using this biomaterial.

Mucilage fractions extracted from Opuntia ficus-indica cactus were captured in calcium alginate biobeads. The beads were tested as eco-friendly adsorbents to remove arsenic (As) from water, and their As removal efficiency was evaluated. Batch adsorption studies were performed using an incomplete factorial design by varying the concentrations of mucilage (0.5–2 mg L−1), sodium alginate (3–5%), and calcium chloride (0.5–1 mol L−1) incorporated in the biobeads. The optimal formulation of these adsorbent biobeads varied depending on the mucilage fraction. Thus, biocomposite formulated with 1.25 mg L−1 of gelling mucilage, 4% of sodium alginate, and 0.75 mol L−1 of calcium chloride eliminated up to 63% of As from water, with a capacity of 101.6 mg g−1, whereas the composite biobeads formulated with 1.25 mg L−1 of non-gelling mucilage reduced 59.8% of As from water, using the least amounts of sodium alginate and calcium chloride in the range tested, with a capacity of 97.1 mg g−1.

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