The structural nature of the synthesized

The structural nature of the synthesized particles was also confirmed by HR-TEM measurements. The HR-TEM images were taken at low (Fig. 3A) and at high (Fig. 3B) magnifications, and similarly to the SEM results depict a nanorods structure. The needle-like structure size ranges up to ∼150nm width and up to 1.5μm length. The crystalline nature of the particles was studied by measuring the SR 3576 manufacturer diffraction of the selected area (Fig. 3C). The highly crystalline nature of the nanorods is evident from the SAED pattern exhibiting a single crystal structure. The measured distances between the fringes are 0.68, 0.21 and 0.22nm, which fit the distances between the (10−1), (313) and (214) lattice planes, respectively. These values match very well the distances reported in the literature for the orthorhombic lattice of the Cu3(OH)4SO4 (PDF No. 01-84-2037).

Mechanism of sonochemical formation of antlerite
In the current study, the antlerite mineral was synthesized from aqueous solution of copper sulfate under ultrasound irradiation. This process does not involve an addition of external hydroxide source. The pH of the copper sulfate pentahydrate solution before sonication was 3.23, and after sonication the value changed to 2.54. The yield obtained in the reaction under the current conditions was low, 0.07%. Increasing the reaction time to 60min, had led to complete dissolution of the product. The explanation for the low yield might be due to the fact that the antlerite is known to be soluble in acidic environment, and the by product in the present reaction is H2SO4. Therefore, the low yield is a result of the solubility of the antlerite in the formed acid.
In order to increase the yield, the reaction was conducted in the presence of urea (pH=4). At the end of the reaction the pH was 3.79. The obtained yield of antlerite was 50times larger, namely 3.5% and this is due to the fact that antlerite is stable between pH 2.5 and 4 [18]. Above pH 4 antlerite is no longer stable and another structure of mineral is formed: brochantite [Cu4SO4(OH)6], this form is stable in pH of 4–6. The increase in the reaction time has also an influence on the yield and by applying reaction time of 60min, in the presence of urea, a significant improve in the amount of antlerite was obtained (21.7%).
Further increase of the reaction time leads to the following yields: 90min reaction results in ∼17.2% product that is not far from the yield of 60min. However, when a reaction was conducted for 120min, the yield was higher (30.1%). The crystalline structure of the products was verified by XRD, and confirmed as pure antlerite phase (PDF 01-84-2037). In addition, the morphology of antlerite from different irradiation times was analyzed. TEM images of 4 antlerite samples (A–D) collected from different irradiation times: 25, 60, 90 and 120min are depicted in Fig. 4. The results reveal that the particle’s size is not influenced by time up to 90min, and slightly increased when a reaction time of 120min was applied. The length of the rods was increased from 1μm to 2.2μm, and the width up to 370nm.
The influence of the amplitude on the yield was also studied, while the reaction time was kept constant, namely 25min. By increasing the amplitude from 25% to 30% and 40%, the yield has been increased from 3.5% to 9.1% and 15.65%, respectively.
In addition the effect of temperature was studied and we performed the reaction for 25min at 30°C by using an ice-water bath. In such conditions, no precipitation was obtained at the end of the reaction.
In order to prove the effect of ultrasound irradiation on the formation of crystalline antlerite, the reaction was carried out without sonication and the reactants were heated up to 70°C for 1h. Materials have not precipitated. This indicates that the conditions that are developed during the bubble collapse (pressure is above 1000atm and the temperature is higher than 5000K) lead to the formation of the crystalline mineral. The fact that US irradiation can induce strong local heating is probably the reason of the formation of antlerite at 60°C under US.