ABSTRACT
This work aimed to synthesize and characterize the calcium acetate monohydrate (Ca(CH3COO)2·H2O) from the exothermic reaction between CaCO3 powder derived from cockle shells with three different acetic acids (8, 10, and 12 mol L-1) concentrations by the rapid and easy process without pH and temperature control to lead to cheap chemical production. The physicochemical characteristics of all synthesized Ca(CH3COO)2·H2O samples are investigated based on the chemical compositions, crystal structures, vibrational characteristics, morphologies, and thermal behavior to confirm the target compound. A suitable concentration of 10 mol L-1 CH3COOH was chosen to produce Ca(CH3COO)2·H2O with the highest yield (96.30 %), maximum calcium content (96.2 % CaO) with lower impurities, and time consumption of 17 h. The calcium acetate product obtained from cockle shells in this work shows differences in thermal stability, morphological structure purity, %yield, and metal contamination with those reported obtained from other sources and another shell type in the previous work. This research investigates the transformation of cockle shell waste into CaCO3 for the production of calcium acetate, aiming to address environmental sustainability concerns by reducing the use of calcium ore resources and greenhouse gas emissions.
ABSTRACT
This work presents the efficient, green, and low-cost preparation of calcium lactate by using bivalve-shell wastes (cockle, mussel, and oyster shells) as raw materials. Three bivalve shells, a cockle, mussel, and oyster, were used separately as an alternative calcium-source material for the preparation of calcium lactate. The bivalve-shell waste was cleaned and milled, obtaining calcium carbonate (CaCO3) powder, which reacted to the lactic acid, forming calcium lactate. The effects of different calcium sources (cockle, mussel, and oyster) and different lactic acid concentrations (6, 8, and 10 mol/L) on the physicochemical properties of the synthesized calcium lactates were then investigated. The results pointed out that the highest solubility of the product was observed when 6 mol/L lactic acid and cockle-shell derived CaCO3 were employed for the calcium lactate preparation. The thermal decompositions of all calcium lactates occurred in three processes: dehydration, ethyl-lactate elimination, and decarbonization, respectively. The results, obtained from an infrared spectrometer, X-ray diffractometer, thermogravimetric analyzer, and scanning electron microscope, confirmed the formation of calcium lactate pentahydrate (Ca(CH3CHOHCOO)2·5H2O). The diffractograms also indicated the presence of two enantiomers of Ca(CH3CHOHCOO)2·5H2O, namely, of dl- and l-enantiomers, which depended on the lactic acid concentration used in the preparation process. The morphologies of calcium lactates show the firewood-like crystals in different microsizes, together with smaller irregular crystals. In summary, this work reports an effective process to prepare the valuable calcium lactates by using the cheap bivalve-shell-derived CaCO3 as a renewable calcium source.
ABSTRACT
The scallop shell waste (Pectinidae, one of saltwater clams) was used as a raw material (precursor) to prepare calcium lactate (Ca(C2H4OHCOO)2), and the physicochemical properties of scallop-derived calcium lactate were then investigated. The scallop waste was first ground to obtain calcium carbonate (CaCO3) powder, and the calcium lactate compounds were successfully synthesized by the reactions between shell-derived CaCO3 and lactic acid (C2H4OHCOOH). The short preparation time, high percentage yield, and low-cost production are the preferred manners, and, in this research, it was the reaction of 70 wt % lactic acid and scallop-derived CaCO3. The thermal decompositions of both CaCO3 precursor and all prepared calcium lactates resulted in the formation of calcium oxide (CaO), which is widely used as a catalyst for biodiesel production. By comparing with the literature, the results obtained from the characterization instruments (infrared spectrophotometer, X-ray diffractometer, thermogravimetric analyzer, and scanning electron microscope) confirmed the formation and crystal structure of both CaCO3 and its calcium lactate product. The morphologies of calcium lactate show different sizes depending on the acid concentration used in the reaction process. Consequently, this work reports an easy, uncomplicated, low-cost technique to change the cheap calcium compound product (scallop CaCO3) derived from shellfish waste to the valuable compound (calcium lactate), which can be used in many industries.
ABSTRACT
Triple superphosphates [TSPs, Ca(H2PO4)2·H2O] were produced by exothermic reactions of oyster shells and different concentrations of phosphoric acid (10, 20, 30, 40, 50, 60, and 70% w/w) in a molar ratio of 1:2. The percentage yields, P2O5 and CaO contents, metal impurities, and thermal behaviors of all the as-prepared products are dependent on the concentrations of phosphoric acid added during the production processes, which confirm to get the best optimum of 60% w/w phosphoric acid. All the as-prepared products were characterized by several characterization methods [X-ray fluorescence, thermal gravimetric/derivative thermal gravimetric analysis, powder X-ray diffraction, Fourier-transform infrared spectroscopy, and scanning electron microscopy], verifying that all the obtained compounds are TSP that can be used as fertilizers without metal toxic contaminants. From the successful results, the method for TSP production can be applied in the fertilizer industry based on starting waste materials of oyster shells that can replace the use of unsustainable phosphate or calcium minerals obtained from nonliving things.
ABSTRACT
The search for sustainable resources remains a subject of global interest and the conversion of the abundantly available bivalve shell wastes to advanced materials is an intriguing method. By grinding, calcium carbonate (CaCO3) powder was obtained from each shell of bivalves (cockle, mussel, and oyster) as revealed by FTIR and XRD results. Each individual shell powder was reacted with H3PO4 and H2O to prepare Ca(H2PO4)2·H2O giving an anorthic crystal structure. The calcination of the mixture of each shell powder and its produced Ca(H2PO4)2·H2O, at 900 °C for 3 h, resulted in rhombohedral crystal ß-Ca3(PO4)2 powder. The FTIR and XRD data of the CaCO3, Ca(H2PO4)2·H2O, and Ca3(PO4)2 prepared from each shell powder are quite similar, showing no impurities. The thermal behaviors of CaCO3 and Ca(H2PO4)2·H2O produced from each shell were slightly different. However, particle sizes and morphologies of the same products obtained from different shells were slightly different-but those are significantly different for the kind of the obtained products. Overall, the products (CaCO3, Ca(H2PO4)2·H2O, and Ca3(PO4)2) were obtained from the bivalve shell wastes by a rapidly simple, environmentally benign, and low-cost approach, which shows huge potential in many industries providing both economic and ecological benefits.
ABSTRACT
Egg consumption is very high throughout the world and with it comes enormous amount of waste eggshells. To reduce and utilize these wastes, eggshell wastes were simply transformed to low- or high-purity calcium carbonate grades by washing, crushing, and drying to use as raw materials for producing highly valuable calcium phosphate products. Low-purity calcium carbonate grade was used to prepare triple superphosphate for using in fertilizer industry, whereas high-purity calcium carbonate grade was used to produce dicalcium phosphate dihydrate, monocalcium phosphate monohydrate, and tricalcium phosphate for using in mineral feed and food additive industries. All calcium phosphate samples obtained by simple, rapid, cheap, and environmentally safe method using eggshells and phosphoric acid were identified and their structural phases and impurities were determined by XRF, XRD and FTIR techniques. Thermal behaviors of raw materials and the prepared calcium phosphates excepted tricalcium phosphate were investigated by TG/DTG techniques. The methodologies described here will be useful to manage eggshells by converting them to highly valuable products, which can solve eggshell wastes problem from industries and communities. This finding supports the viewpoint of zero waste operation to produce value-added products for obtaining sustainable development, which may be selected as an alternative way for material recycling and waste management in the future.
