**1. Introduction**

Metal-processing industries would undoubtedly have a challenge in disposing of metal-bearing effluents. Most industries dishonestly discharge their effluents into surrounding drains and water streams, either untreated or partially treated [1] due to increase in overall industrial cost. Industries such as alloys, pigments, electroplating,

mining, metallurgical activities, nuclear power plant operations, aerospace industries, electrical contacts, printing, and the manufacture of paper, rubber, plastics, and batteries play a major role in water pollution by releasing heavy metal ions in their effluents [2].

Nickel, a non-biodegradable hazardous metal ion, is the heavy metal ion studied in this work [3]. Ni(II) ions in drinking water are allowed to be at a concentration of 0.02 mg/L. Anaemia, diarrhoea, encephalopathy, hepatitis, lung and kidney damage, gastrointestinal distress, pulmonary fibrosis, renal edoema, skin dermatitis, and central nervous system dysfunction are just some of the negative health impacts of exceeding the permissible limit [4]. As a result, before being discharged into the environment, industrial effluents containing Ni(II) must be treated [5].

Traditional methods for removing Ni(II) metal ions include coagulation, electro dialysis, flotation, ion exchange, precipitation, reverse osmosis, and others [6]. Low competency performances, especially when using these methods on very small concentrations of metal ions [7], are some of the limitations of these traditional approaches.

Adsorption with a low-cost sorbent is a frequently used approach in the treatment of industrial effluents [8]. However, it is still necessary to develop a low-cost, readily available, high-adsorption-capacity waste water treatment material that can address the aforementioned environmental concerns [9]. Because it is efficient, avoids secondary wastes, and utilises low-cost resources, biosorption onto live or non-living biomass, such as fungi, bacteria, yeast, moss, aquatic plants, and algae, can be a viable approach for removing heavy metals from their source [10]. Marine algae in coastal locations play a significant role in world ecology, are exceedingly efficient, and are taxonomically varied [11]. Many sections of the world gather or produce marine macroalgae, making them easily accessible in huge amount in the manufacture of very efficient bio sorbent resources [12]. The goal of this study is to utilise Blue Green Marine Algae (BGMA) as an adsorbent to adsorb the metal ions Ni(II) present in an artificial aqueous solution [13].

There is a scarcity of relevant literature on Ni(II) adsorption with three, four, and five parameter models [14, 15]. The constraints of the simple, one- and two-parameter models would be overcome by the high-parameter models. The use of large parameter models to describe the adsorption process under equilibrium conditions can provide highly clear and accurate information. The purpose of this work is to determine the biosorption capacity of BGMA for the removal of Ni(II) metal ions from a synthetically generated stock solution under optimal experimental circumstances of pH 6, 2 g biomass loading, and 120 rpm agitation speed. In addition, the experimental data is examined using one, two, three, four, and five parameter isotherm models. For the purpose of modelling, the experimental data is examined using one, two, three, four, and five parameter isotherm models.
