Catalytic Ozonation using Iron-Doped Water Treatment Sludge as a Catalyst for Treatment of Phenol in Synthetic Wastewater

In this study, iron (Fe)-doped water treatment sludge, designated as Fe/WTS, was prepared by a hydrothermal method using phosphoric acid and impregnation with ferric nitrate. The results from X-ray diffraction (XRD) confirmed the presence of Fe loaded on the WTS support, while Brunauer-Emmett-Teller (BET) analysis indicated an increase of specific surface area of the WTS from 37.37 m2/g to 118.51 m2/g after acid modification. The Fe/WTS was successfully used as a catalyst in catalytic ozonation for degradation of phenol in synthetic wastewater. Factors affecting phenol removal efficiency including reaction time, pH, catalyst dosage, and Fe content were investigated. At the optimum condition, i.e., reaction time of 120 min, pH of 11, catalyst dosage of 1 g/L, and Fe content of 2% (w/w), the removal efficiency of phenol was 99.16% which was higher than that of sole ozonation (44.61%). The results of kinetic analyses indicated that the reactions of catalytic ozonation in the presence of Fe/WTS and WTS catalysts followed pseudo-first order kinetic model with rate constants of 0.0362 and 0.0065 min-1, respectively, while that of sole ozone was 0.0046 min-1. This finding presented the potential use of Fe/WTS as a novel catalyst for catalytic ozonation

Conversion of Bivalve Shells to Monocalcium and Tricalcium Phosphates: An Approach to Recycle Seafood Wastes

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 β-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

Recrystallization of Triple Superphosphate Produced from Oyster Shell Waste for Agronomic Performance and Environmental Issues

Calcium dihydrogen phosphate monohydrate (Ca(H2PO4)2·H2O) (a fertilizer) was successfully synthesized through a recrystallization process using prepared triple superphosphate (TSP) derived from oyster shell waste as the starting material. This bio-green, eco-friendly process to produce an important fertilizer can promote a sustainable society. The shell-waste-derived TSP was dissolved in distilled water and kept at 30, 50, and 80 °C. Non-soluble powder and TSP solution were obtained. The TSP solution fractions were then dried, and the recrystallized products (RCP30, RCP50, and RCP80) were obtained and confirmed as Ca(H2PO4)2·H2O. Conversely, the non-soluble products (NSP30, NSP50, and NSP80) were observed as calcium hydrogen phosphate dihydrate (CaHPO4·2H2O). The recrystallized yields of RCP30, RCP50, and RCP80 were found to be 51.0%, 49.6%, and 46.3%, whereas the soluble percentages were 98.72%, 99.16%, and 96.63%, respectively. RCP30 shows different morphological plate sizes, while RCP50 and RCP80 present the coagulate crystal plates. X-ray diffractograms confirmed the formation of both the NSP and RCP. The infrared adsorption spectra confirmed the vibrational characteristics of HPO42−, H2PO4−, and H2O existed in CaHPO4·2H2O and Ca(H2PO4)2·H2O. Three thermal dehydration steps of Ca(H2PO4)2·H2O (physisorbed water, polycondensation, and re-polycondensation) were observed. Ca(H2PO4)2 and CaH2P2O7 are the thermodecomposed products from the first and second steps, whereas the final product is CaP2O6

Simple and Rapid Synthesis of Calcium Acetate from Scallop Shells to Reduce Environmental Issues

The search for sustainable resources remains a subject of global interest. Calcium acetate used in many fields was prepared using waste scallop shell as a raw material, and its physicochemical properties were investigated. The waste scallop shells were transformed to calcium acetate compounds by reactions with four acetic acid concentrations at ambient temperature until the completely dried powder is obtained. The maximum yield of 87% with short reaction time at a low temperature was observed in the reaction of 60%w/w acetic acid with scallop shells. Thermal transformation reactions of all prepared calcium acetate samples revealed temperature conditions for heating to produce other advanced materials. FTIR and XRD results confirmed the purity and solid phase of all prepared calcium acetate samples, and they were compared with those of literatures and found to be well consistent. The obtained timber-like particles have different sizes depending on the acetic acid concentration. This work reports an easy and low-cost method with no environmental effect to produce cheap calcium products to be used in the industry

Efficient, Green, and Low-Cost Conversion of Bivalve-Shell Wastes to Value-Added Calcium Lactate

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