Superior removal of Co2+, Cu2+ and Zn2+ contaminants from water utilizing spongy Ni/Fe carbonate–fluorapatite; preparation, application and mechanism

Abstract Spongy Ni/Fe carbonate - fluorapatite was synthesized from natural phosphorite enriched with iron impurities. The morphological, chemical and structural features of the product were estimated using several techniques as XRD, SEM, EDX, and FT-IR. It exhibits spongy structure of nano and micro-pores. The average crystallite size is about 8.27 nm. The suitability of the product for considerable decontamination of Zn 2+ , Co 2+ , and Cu 2+ , ions from water was studied based on several reacting parameters. The equilibrium was attained after 240 min for Zn 2+ and Co 2+ ions while the adsorption equilibrium of Cu 2+ reached after 120 min. The adsorption data for the selected metals was represented well by a pseudo-second-order model which revealed chemisorption uptake. The equilibrium studies were appraised based on traditional models and two advanced models were designed according to the statistical physical theories. The adsorption results highly fitted with Langmuir model followed rather than the other models. This indicated a monolayer adsorption for the metal ions by spongy Ni/Fe carbonate - fluorapatite. The estimated q max values are 149.25 mg/g, 106.4 mg/g and 147.5 mg/g for the uptake of Zn 2+ , Co 2+ , and Cu 2+ , respectively. Based on monolayer models of one energy and two energies, the number of receptor adsorption sites, number of adsorbed metal ions per active site, the average number of sites which occupied by ions, mono layer adsorption quantity and the adsorption quantity after total saturation were calculated for the first time for such materials.