Channeling Unavoidable Food Waste Towards The-fluoridation

Abstract

Air, water, and food are the three basic needs for the survival of mankind. Earth's surface is enclosed with two third of the water. But the availability of quality freshwater is one of the most critical environmental issues. Pollutants are the major factor for water pollution. Fluorine is the 13th richest element present on the earth's crust. Fluoride is considered as a “two-edged sword” because its deficiency leads to dental caries while excess amount leads to dental and skeletal fluorosis. Adsorption is considered as an efficient process to defluoridate the water. On the other hand, food waste is on the raise. Approximately 1.3 billion tonnes of food gets lost or wasted every year, which is nearly one-third of the food produced in the world for human consumption. The main aim of this chapter is to bring unavoidable food waste to light to society so that it can be used as an adsorbent.

Keywords: Deflouridation, Adsorbent, Fluoride, Food waste, Food waste

Introduction

“Not every trash is a trash

Can be transformed into treasure too….” 

Water is the most abundant and is an essential component of our life-supporting system. Water is present in each and every cell of our body, various tissues, and compartments. Therefore, the nutritional recommendation of water is higher during the growth period. Water acts as a solvent, a reaction medium, a reactant, and a reaction product. Water is necessary for cellular homeostasis because it transports nutrients to cells and removes wastes from cells. It is the medium in which all transport systems function allowing exchanges between cells, interstitial fluid, and capillaries.

Water quality is affected by different pollutants. Also, the long discharge of industrial effluents, domestic sewage, use of fertilizers & pesticides, and waste dump cause groundwater pollution and health problems created.

Food Waste is defined as waste generated during the preparation of meals and any food that is not consumed. It also includes food that has been thrown away, not used, or partly used. It does not include packaging materials. Food waste may have meat excluded i.e. vegetable peelings, fruit scraps, teabags, coffee grounds, egg shells, etc. Alternatively food waste can have meat included and so include cooked food, meat, fish, bones, etc.

The types of food waste may be summarized as avoidable, potentially avoidable, and unavoidable food waste.

• 60 % is avoidable food waste (eg: plate scrapings, leftovers, gone-off fruit, and vegetables, passed its date perishables, etc.).
• 20 % is potentially avoidable food waste (eg: bread crusts, potato skins, etc.).
• 20 % is unavoidable food waste (eg: general rubbish, banana skins, chicken bones, etc.)

This food waste can be reduced, reused, and recycled. The review of the literature shows that unavoidable food waste also has health benefits and functional properties. So this unavoidable food waste can be used effectively. One of the properties of some unavoidable food waste is its ability to fluoridize.

Fluoride is considered as a natural contaminant for groundwater resources globally. Fluorine is the 17th most abundant element in the earth’s crust. It is a gas and never occurs in a free state in nature. Fluorine is essential for the normal mineralization of bones and the formation of dental enamel. Fluoride is often considered as a “two-edged sword” because deficiency of fluoride intake leads to dental caries while excess consumption leads to dental and skeletal fluorosis. According to the World Health Organisation, the maximum acceptable limit of fluoride concentration in drinking water is 1.5 mg/l. The maximum limit of fluoride in drinking water for human consumption is 1.0 mg/l. According to the National Programme for Prevention and Control of Fluorosis high levels of Fluoride were reported in 230 districts of 20 States (after the bifurcation of Andhra Pradesh in 2014).

Fluoride enters the human body mainly through drinking water and also partly through foods. It is absorbed through the gastrointestinal and respiratory tract; distributed via blood and gets deposited in bones and teeth. Acute toxicity occurs after ingestion of a few fluoride compounds for a short period of time which then leads to poisoning. Symptoms include nausea, vomiting, hypersalivation, abdominal pain, and diarrhea. In severe or fatal cases, these symptoms are followed by convulsions, cardiac arrhythmias, and coma. The other symptoms are collapse with paleness, weakness, shallow breathing, weak heart sounds, wet, cold skin, cyanosis, dilated pupils, hypocalcemia, and hyperkalemia, and into two to four hours even death. Other possible effects include muscle paralysis, carpopedal spasms, and extremity spasms.

Chronic exposure causes dental fluorosis and skeletal fluorosis. Dental fluorosis is characterized by discoloration, mottling of teeth, lusterless, opaque white patches in the enamel, which may become stained yellow to dark brown, and in severe forms cause marked pitting and brittleness of teeth. Prolonged exposure of fluoride results in fragile bones having low tensile strength known as skeletal fluorosis. Fluoride toxicity at a high level leads to thyroid changes, growth retardation, kidney changes, and even urolithiasis. Like lead, even a minute dose of fluoride accumulation damages the brain and development of children. Also produces abnormal behavior in animals and reduces humans' IQ too.

Situation In Tamil Nadu

Among the drinking water samples tested for fluoride, 14% of them showed to have levels above 3ppm/l and 86% had fluoride levels above 1.5ppm/l, which were higher than the permissible levels. In Tamilnadu water samples collected from districts like Dharmapuri, Krishnagiri and Dindigul resulted in fluoride content above 1.5mg/l.

The de-fluoridation methods are divided into three basic types of modes of action.

1. Chemical reaction with fluoride – Nalgonda technique
2. Adsorption process- eg. Charcoal prepared from bone, activated carbon, activated magnesia, tamarind gel, serpentine, activated alumina, plant material, burnt clay.
3. Ion- exchange process- Anion/ Cation exchange resins

Unavoidable Food Waste Towards De-Fluoridation

A biosorbent was prepared by loading Al/Fe oxide onto tea waste. It was tested against drinking water with fluoride. It was found that the combination of Tea and Al or Tea-Al and Fe could effectively reduce the fluoride concentration to below 1.5 mg/l in the drinking water and also the residual concentrations of Al and Fe in the drinking water after Tea-Al-Fe treatment were below the WHO standards at pH values ranging from 5 to 10. The maximum fluoride adsorption capacities for the original tea, Tea-Fe, Tea-Al, and Tea-Al-Fe biosorbents were 3.83, 10.47, 13.79, and 18.52 mg/g, respectively.

Ganvir and his co-workers studied the effect of rice husk ash to remove fluoride from drinking water. Rice husk ash which is an abundantly available material was prepared by burning rice/paddy husk. The adsorption experiments were carried out by using 0.1 g of adsorbent concentration per liter of water containing fluoride at a range of 10–60 mg/L at pH 7. All the experiments were conducted at 27°C for 1 hr. The adsorption capacities of the modified rice husk ash and column study for defluoridation were found as 15.08 and 9.5 mg/g. It was concluded that the removal of fluoride is depending upon a strong pH value.

Potato peel in combination with rice husk ash was used as an adsorbent for the removal of As and F from contaminated water. It was found that the maximum adsorption capacity of adsorbents for As and F− was 2.17 μg g−1 and 2.91 mg g−1, respectively. The fluoride removal was observed between pH 7 and 9. Thus it was concluded that in fluoride-contaminated water streams these adsorbents can be used for filtering both arsenic and fluoride.

In batch and column test, chemically modified rice husk and corn cob activated carbon was investigated for fluoride removal. It was tested in three variations such as 100% corn cob activated carbon and 50% rice husk + 50% corn cob activated carbon. It was found that adsorption capacities were 7.9, 5.0, and 5.2 mg/g. In the batch test, the maximum adsorption capacity for rice husk and corn cob activated carbon were 7.9 and 5.8 mg/g, and removal efficiency of 91% and 89% were achieved.

In batch mode, maize husk fly ash was tested for its ability to eliminate fluoride from water. The greatest fluoride elimination was seen to be 86% at an ideal condition. This maximum evacuation was observed at an agitation rate of 250 RPM at pH 2, 2.0 g/50 ml of dosage and an equilibrium time of 120 mins.

Christina and Viswanathan studied, saponified orange peel residue (SOPR) and Fe3O4 nanoparticles immobilized SOPR (FNPSOPR) for the efficient removal of fluoride from water. The maximum adsorption capacity of FNPSOPR was found as 80.33 mg/g at a sorbent concentration of 0.25 gL−1.

Nasr and his fellows observed cuttlefish bone as an adsorbent material (available in Tunisia) for the defluoridation of water. It was concluded that the cuttlefish bone has excellent efficiency for the removal of fluoride. Thus cuttlefish bone has 80% efficiency to remove fluoride from water. It was obtained at pH 7.2, 1 h contact time, 15 g/L adsorbent dose, and 5 mg/L initial fluoride concentration.

Research study shows that the powder of Sawdust of Indian Rosewood (Dalbergia sissoo), wheat straw (Triticum spp.), and bagasse of sugarcane resulted in better removal of fluoride in water. The material was dried in an oven at 105 ◦C for 24 h, and then sieved in the size range of 20–50 mesh ASTM. The fluoride concentration was reduced significantly from 3.14 to 1.31, 1.59, and 1.71 mg L−1 for bagasse of sugarcane, sawdust, and wheat straw respectively.

The coconut fiber ash was prepared by drying the coconut fiber in a muffle furnace at 423 K for one and half hours then it was washed with distilled water, and dried in sunlight. The dried fiber was then dried in an oven at 353 K for overnight. It was sieved through 150mm mesh. Then it was impregnated with aluminum (AICFA) for remove of fluoride from drinking water. The effect of adsorbent to remove fluoride from groundwater was conducted without adjusting the pH of the experimental samples at the rate of 0.5 g/L AICFA under identical experimental conditions of the equilibrium batch adsorption study. The fluoride level of reduced from 6.01 ± 0.11 to < 0.96 mg/L.

rch on eggshell powder as an adsorbent for removal of fluoride from aqueous solution using the batch technique was conducted. The maximum adsorption of fluoride was achieved at pH 2.0-6.0. Around 94% defluoridation was achieved at an initial metal ions concentration of 5 mg/l at an optimum dose of 2.4 g/100ml and an optimum time of 120minutes.

Using shrimp shell waste the initial fluoride concentration of 8 mg/L, was removed about 80% at pH 11 within 15 minutes of contact time, and the adsorbate dose of 8mg/ L. The research also shows that the removal percentage of F increased with increasing adsorbent dose from 3.2 g/L to 64 g/L, but there was no difference between 48 g/L and 64 g/L.

Banana peel, groundnut shell, and sweet lemon peel were used as an adsorbent to remove fluoride from industrial wastewater. It was found that the efficiency of banana peel, groundnut shell, and sweet lemon peel for defluoridation were 94.34, 89.9, and 59.59 % respectively.

The collected banana peel was washed with de-ionized water and dried in a hot air oven at 50 °C for 12 h. The dried peels were cut into small pieces and again dried in a hot air oven maintaining 60 °C temperatures for 24 h. In the column study, a removal percentage of 86.5% was observed.

Java plum (S. cumini) seed adsorbent was prepared by drying the seeds in the sunlight for 2 days and then dried in a hot air oven in the range of 80-100°C for 36 hrs. This experiment was carried out in a reactor column of SS pipe. The reactor is filled with weighted amount of java plum seeds adsorbent having a particle size of 2-4 mm as a fixed-bed absorber. The bed was supported by the cotton pad and closed by rubber, to prevent the flow of adsorbent together with the effluent. The experimental results were encouraging and indicate that java plum seed can be used as a bio-adsorbent to remove fluoride in a fixed bed adsorption process. The optimum dose for the batch system was 3.9 g/50 ml.

Carbonized pomegranate seeds

Pomegranate seeds were dried, carbonized, and ground to fine sizes. It was found that adsorbents at a particle size of 55 µm, at the optimum dosage of 0.75 g, at pH 5.5, and at a contact time of 75 min can act as good adsorbents. They also studied adsorption for a different solution having initial fluoride concentrations 2, 4, 6, 8, and 10 mg/L. And found that when the concentration of fluoride is 2 mg/L efficiency of the adsorbent is 88%, but as the concentration of fluoride increased up to 10 mg/L efficiencies is reduced to 47%.

The collected lemon peels were sun-dried for 5-6 days followed by oven-dried at 80±5˚c for 24 hours, powdered, and then thermally activated (carbonized) at 500±5˚C in a muffle furnace for 1 hr. The obtained ash was washed with distilled water until the pH was 7-7.8 and dried in an oven at 100±5˚C for 24 hr. Nearly, 83% defluoridation was obtained at pH 4.0 in 100 min of contact time at a rotation speed of 125rpm.

Tamarind seed is considered as household waste. Studies revealed that the maximum defluoridation was achieved at pH 7 and defluoridation capacities decreased with an increase in temperature and particle size. It was concluded that for the treatment of 10 litter of drinking water per day for three members of a family having a fluoride concentration of 5 mg/L, required 2.75 g of Tamarind seed per day.

Batch studies on adsorbents such as pineapple peel powder and orange peel powder were conducted. The efficiency of pineapple peel powder to remove fluoride from the water was about 90% at pH 4 with a contact time for one hour, a dose of 0.6 g/L, when 4 mg/L of fluoride is present in 100 ml of water.

Phyllanthus Emblica seeds

Phyllanthus Emblica seed powder sample was prepared by drying at 378-383 k for 24 hr. Followed by washing in doubly distilled water and dried at the same temperature for 3hr. Finally, it was thermally activated in a muffle furnace at 1073 k. The success rate of defluoridation was observed as 82.1% for the 3 ppm initial fluoride concentration and adsorbent dose of 0.75g at room temperature and neutral pH.Advantage Of Unavoidable Food waste As An adsorbent Over conventional adsorbents

• These natural adsorbents are low in cost and can be obtained locally.
• It is an easily available material.
• The efficiencies of fluoride removal of various natural adsorbents vary between 50 and 90% [15].
• To increase the efficiency, adsorbents require simple treatment like alkali and/or acid treatment.
• Since the cost is low these adsorbents can be used once and discarded.
• It requires less maintenance and supervision.
• These adsorbents can be disposed of easily and safely.

Conclusion

From the above-mentioned study, it is demonstrated that the potential utility of this unavoidable waste could be developed into a viable adsorbent for the removal of fluoride from fluoride-contaminated water streams. Through the development of adsorbents from this food waste, human society can avoid food waste even it is an unavoidable waste. Future research can be concentrated on the development of eco-friendly, effective, low cost and easily available adsorbents for the removal of fluoride from water.