Industrial, domestic and agricultural wastewater are the major pollutants contaminating the aquatic environment. Most of wastewater containing toxic materials that when disposal into water streams without specific treatment cause pollution of water bodies. So, it is essential to treat wastewater to remove heavy metals before its disposal to water body. Now, the world trends in the reliable low cost and practical methods for wastewater treatment. This treatment has great necessary to prevent the contamination of receiving water.
Different approaches to remove heavy metal ions from wastewater, including chemical precipitation, ion exchange, reverse osmosis, electro-kinetic remediation, phytoremediation and adsorption have been used. Researches have shown that adsorption is the simplest and best cost-effective method. Adsorbents that applied in the adsorption technique can be recycled and recycled again [1]
Adsorption technology is an attractive process in the water treatment because of its high efficiency, economy trends. The most common adsorbents include activated carbons, zeolites, clays, biomass and polymeric materials [2].
Bones have consisted of 30% organic and 70% inorganic compounds. The major component of bone minerals is hydroxyapatite Ca10(PO4)6(OH)2 (HAP). HAP is considered as an effective adsorbent as it has a high heavy metal removal capacity ion exchange with calcium ions on the surface of bone. Animal bones used as adsorbent for the removal of heavy metals due to their biogenic apatite. They have been used as an adsorbent due to their low-cost, efficient, and natural abundance [3] .
Bone char is a porous, black and granular material produced by heating the animal bones. Its composition varies depending on how it is made; however, it consists mainly of tricalciumphosphate (or hydroxylapatite) 57–80%, calcium carbonate 6–10% and carbon 7–10% [4].
Bone biochar is used widely as adsorbent in water pollution control; because of its high surface area and pore volumes, and thir outstanding physicochemical properties [5]. It characterized by a mesoporous structure with a specific surface area from 80 to 120 m2/g [6]. During last decades several studies have reported the removal of a variety of organic and inorganic compounds from aqueous solutions with bone biochar [7–11]
Due to the negatively charged of the biochars surfaces, it can adobe positively charge metals through electrostatic attractions. Various functional groups and ligands specificity on the surface of biochars can interact with heavy metals forming complexes [12]. Compared with activated carbon, biochar appears to be low-cost and effective adsorbent. High temperature needed for the production of carbon. Ultimately, the biochar production is cheaper with lower energy requirements [13].
Doostmohammadi et al. [14] found that when charring bovine and pig bones under air atmosphere the values of BET specific surface areas were 2.2 and 44 m2 /g, respectively. Murillo et al. [15] reported surface area values of chicken pyrolysis in nitrogen atmosphere about 130 m2/g .
More recently fish bone has been used as adsorbent materials for remediation of wastewater [ 7, 16–19]. Fish bones as a low cost and natural abundance material have proven to be one of the most effective heavy metal adsorbent for wastewater treatment. The adsorption efficiency of fish bones is due to the presence of hydroxyapatite Ca10(PO4)6(OH)2, and this because of the exchange reaction with calcium ions with heavy metals [18]. Also, organic phosphates have high affinities for adsorption to mineral surfaces; so, fish bones waste could be used as a phosphate source for treating heavy metals in wastewater.
Mostofa et al.[20] investgated investigation the adsorption of lead onto apatite extracted from mixed fish bone. Terzioğlu et al.[21] found that the fish bone as a rich resource of calcium phosphates and a low-cost and an abundant material. Fish bones were effective sources to obtain non-toxic calcium phosphates. Nahum et al. [22] used synthesized bone char (BC) from pleco fish (Pterygoplichthys spp.) to remove cadmium and fluoride in water, and found that the capacity of BC for adsorbing Cd(II) was enhanced by increasing the solution pH. Wange et al.[23] prepared activated fishbone charcoal after treatment with K2CO3 as an activating agent and used it for removal of emulsified oil from oily wastewater
Kizilkaya et al. [24] Investigated the removal of Pb from aqueous solutions using pretreated fish bones. They reported that the maximum adsorption capacity for Pb (II) was found to be 323mg/g at optimum conditions.The experiments showed that the kinetic and adsorption isotherms results of adsorption obeyed a pseudo second-order model and fitted well to the Langmuir isotherm. Desorption/leaching experiments showed that desorption of the Pb on the bone surface exhibited very low ratios. Lima et al. [25] studied the removal of Zn ion from aqueous solutions using powdered fish bones, and found high Zn adsorption (98%) at adsorption conditions pH 5.0, adsorbent dose 1.80 g/100 mL, and 12 hr contact time at room temperature 30 ± 1oC.
In the present study, fish bone waste has been used for the preparation of new adsorbents using chemical activation with 0.001 M HNO3, 0.1 M NaOH, 0.5% H2O2, and ethanol, followed by calcination. The concentrations of the activators (0.1 NaOH, and 0.5% H2O2) were not published before. Also, the efficnicy of Pb and Cd adsorption on the prepared adsorbent will be studied. Various factors will be investigated to associate the effectiveness of them in Pb and Cd adsorption from polluted solution.