Transmission electron microscopy analysis of hydroxyapatite nanocrystals from cattle bones 

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CHAPTER 3: Sorption of 17β-estradiol from aqueous solutions on to bone char derived from waste cattle bones: Kinetics and isotherms 

Sorption of 17β-estradiol from aqueous solutions on to bone char derived from waste cattle bones: Kinetics and isotherms

CHAPTER ABSTRACT

This study is aimed at investigating the removal of 17β-estradiol (E2) from aqueous solutions using bone char derived from waste cattle bones. The cattle bones were surface treated with acetone and pyrolysed in an oxygen depleted environment. The obtained bone char was then used for the adsorption of 17β-estradiol. This work involves studying the batch adsorption process with respect to the effect of contact time, initial concentration and dosage of adsorbent. The adsorption kinetic studies revealed that the adsorption of E2 on bone char obeys the pseudo second order kinetic model. In addition, the adsorption kinetics was also assessed for the intraparticle diffusion model. This study shows that the adsorption of E2 on bone char has a very complex mechanism involving the diffusion process. Increasing the bone char dosage led to an increase in the removal of E2. With a bone char dosage of 50 g L-1, about 95.3% of E2 was removed from aqueous solutions. The experimental adsorption isotherm data was fitted to Langmuir and Freundlich isotherm models. The saturated bone char was regenerated using ethanol/water solution. The preliminary reusability study showed that the adsorption capacity was restored to 85% of its initial capacity in the third cycle.

Introduction

Soils as our natural capital assets need to be well preserved to maintain their quality to be productive for farmland use and livestock rearing. Water being the most vital ingredient influences the soil quality to a significant level. Therefore, its quality needs to be controlled to be free of pollutants by economical means. There is also a huge pressure on the pastoral landscape which is becoming more dynamic and sophisticated by the day.
There are several natural and synthetic chemicals that interfere with the endocrine system of humans and animals. These are known as the endocrine disruptive chemicals (EDCs) which have antagonistic effect on the aquatic species and human beings. Research shows that a variety of chemicals enter the environment and the amounts are increasing day by day [11]. Only 20% of the animals urine is taken up by the grass and the rest goes down directly to the water ways resulting in 40% of New Zealand’s lakes becoming worse [122]. In addition, due to the growing dairy demands, there is an expansion of the dairy industry being planned in Waikato and Canterbury region. Researchers say, growing plants across the river banks are unable to stop the animal wastes getting into the water ways [122].
There are some EDCs which are being commissioned nationwide along with gaining the international regulatory attention [11]. A number of survey reports were presented where the ubiquitous presence of EDCs were identified in receiving water ways and treated effluents [32]. Also, there are several reports on the adverse effects of these EDCs, which include reproductive abnormalities in fishes and alligators. An unusual sexual behavior was observed in female herring gulls. In addition, animals were observed to have thyroid problems, metabolism changes and defects in off springs, whereas humans developed cryptorchidism, hypospadias and testicular cancer [10]. EDCs include a wide range of synthetic and natural chemicals. But among them, the steroid hormones are the most potent ones. The steroid hormones commonly found in the waste waters are estrone (E1), 17β-estradiol (E2), estriol (E3) and 17α-ethinylestradiol (EE2) [123]. These hormones reach the environment through the animal wastes and sewages since all humans and animals excrete these steroid hormones. Therefore, an efficient and cost effective treatment process needs to be developed.
Presently, the treatment technologies to remove these EDCs from the wastewater include adsorption, advanced oxidation, biological degradation and membrane filtration [124]. Adsorption using activated carbon (AC) is generally used to remove organic pollutants which has proved to be a promising method to remove estrogens. Usually, these activated carbons are manufactured from a wide range of carbon based materials. Due to high surface area and porosity these AC is efficient in adsorbing pollutants [103], but the regeneration of the used AC proves to be a difficult task. Recently, many new adsorbents are being prepared and tested for their efficiency in estrogen removal. These include activated carbon prepared from agro wastes [125], slurry wastes [126], chitin [127], moso bamboo [128] and biochar [129].
Nowadays, bone char is being explored for its adsorption capacity and efficiency. Bone char is a readily available source which is prepared by pyrolysis process, where they undergo a thermal treatment at a range of 400 -500 oC in a limited supply of air. It has a long history of removing color from sugar solution, defluoridation and removing heavy metals but to the best of our knowledge, it has not been used for the removal of estrogens. Being a mixed adsorbent having about 80-90% hydroxyapatite and 10% amorphous carbon, it gets distinguished from other available adsorbents [103]. It has already proved its efficiency in removing pyrogen such as endotoxin [93], air pollutant [90], bacterial spores [130], heavy metals [63, 80, 131], dyes [88, 89] and organic compounds [70] from aqueous solutions.
This study demonstrates the use of bone char as a new class of solid adsorbent for treating E2 from water. 17β-estradiol is human sex hormone which is essential for the development of female reproductive tissues including bone health. It has been selected for this study since it is persistent in treated effluents and highly estrogenic. The efficiency of the bone char has been studied in a batch adsorption process.

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Experimental

Bone char prepared under laboratory conditions was tested for the adsorption of E2 in water. Cattle bones (bovine and bull) were obtained from Biomaterials Laboratory. 17β-estradiol (≥98%), sodium chloride (≥ 99.5%) was purchased from Sigma- Aldrich. Details on E2 characteristics are shown in Table 3.1. Acetonitrile (HPLC grade) was supplied by Tedia and deionised water (18.2 MΩ) was obtained from the laboratory MilliQ water purification system.
Stock solutions were prepared at a concentration of 200 mg L-1 by dissolving the solid compound in ethanol and stored at 5 oC. Working aqueous solutions of the standards were prepared by diluting the stock solution with deionised water. Following this procedure predetermined concentration of E2 solutions were prepared for calibration measurements.

Preparation of bone char

Bone char was prepared from waste cattle bones. The bones were initially washed and boiled in deionised water for about 3-4 h to get rid of the protein pieces. These cleaned bones were dried in an oven (Contherm, Thermotec 2000) at 110 oC for 80- 85 h and were allowed to cool at room temperature. After this, the bones were broken down and ground to a desired mesh size 1-2 mm. The obtained granules were treated with acetone followed by washing with hot distilled water. These washed samples were dried and transferred to a muffle furnace to carry out the pyrolysis process in a limited supply of air.

CHAPTER 1 : Introduction 
1.1 Introduction
1.2 Release of contaminants in New Zealand water
1.3 Chemistry of selected estrogens
1.4 Evidence for endocrine disruption in wildlife and aquatic population
1.5 Dairy Effluent Treatment
1.6 Sustainable Agriculture
1.7 Research Objectives
1.8 Thesis Framework
CHAPTER 2: Synthesis and Characterization of mesoporous bone char obtained by pyrolysis of animal bones 
Chapter Abstract
2.1 Introduction
2.2 Experimental
2.3 Results and Discussion
2.4 Summary
CHAPTER 3: Sorption of 17β-estradiol from aqueous solutions on to bone char derived from waste cattle bones: Kinetics and isotherms 
Chapter Abstract
3.1 Introduction
3.2 Experimenta
3.3 Adsorption Experiments
3.4 Results and Discussion
3.5 Summary
CHAPTER 4: Comparative studies of 17β-estradiol sorption on raw bone powder, bone char, and commercial hydroxyapatite.
Chapter Abstract
4.1 Introduction
4.2 Materials and Methods
4.3 Adsorption Experiments
4.4 Results and Discussion
4.5 Adsorption studies
4.6 Summary
CHAPTER 5: Transmission electron microscopy analysis of hydroxyapatite nanocrystals from cattle bones 
Chapter Abstract
5.1 Introduction
5.2 Experimental Section
5.3 Results and Discussion
5.4 Summary
CHAPTER 6: Surface chemistry and textural characterisation of activated carbon prepared from animal bone chars, using potassium hydroxide (KOH) as an activating agent 
Chapter Abstract
6.1 Introduction
6.2 Experimental
6.3 Results and Discussion
6.4 Summary
CHAPTER 7: Summary, Recommendation and Future Works 
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Adsorption of 17β-Estradiol on to Bone char derived from Cattle bones

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