A cost-effective and eco-friendly biosorption technology for complete removal of nickel ions from an aqueous solution: Optimization of process variables

The enormous industrial usage of nickel during its manufacture and recycling has led to widespread environmental pollution. This study was designed to examine the ability of Gelidium amansii biomass to biosorb Ni2+ ions from an aqueous solution. Six independent variables, including contact time (1.0 and 3.0 h), pH (4 and 7), Ni2+ concentration (25 and 200 mg·L−1), temperature (25°C and 50°C), G. amansii biomass (1.0 and 4.0 g·L−1), and agitation mode (agitation or static), were investigated to detect the significance of each factor using a Plackett–Burman design. The analysis of variance for the Ni2+ biosorption percentage indicated that three independent variables (contact time, temperature, and agitation–static mode) exhibited a high level of significance in the Ni2+ biosorption process. Twenty experiments were conducted containing six axial, eight factorial, and six replicates points at center points. The resulting face-centered central composite design analysis data for the biosorption of Ni2+ exhibited a very large variation in the removal percentage of Ni2+, which ranged from 29.73 to 100.00%. The maximum Ni2+ biosorption percentage was achieved in the 16th run with an experimental percentage quantified as 100.00% under the experimental conditions of 3 h of incubation time and 45°C with 100 rpm for agitation speed.