Titanium xerogel coagulant (TXC) is a new type of coagulant that has attracted much attention in recent years. However, the tetracycline removal performance of TXC was not satisfactory because low isoelectric point (pH iep ) inhibited the electrical neutralization efficiency of TXC in an alkaline environment. To overcome this shortcoming, a composite xerogel coagulant (titanium-aluminum xerogel composite coagulant) was prepared. The removal of tetracycline and turbidity was used as evaluation indexes. It was proved that the combination of aluminum (III) and titanium (IV) enhanced the resistance of TXC to pH. The synthesized titanium-aluminum xerogel composite coagulant (TXAC) has an excellent removal ability of tetracycline in a wide pH range (pH = 5–10). At pH 8.8, the dosage required to remove 80% tetracycline from water decreased from 93 (TXC) to 35 mg/L (TXAC). The reason for this improvement could be attributed to (i) aluminum (III) enhanced the electric neutralization of TXC to negatively charged pollutants in an alkaline environment; (ii) the complexing ability of organic matter and aluminum (III) was enhanced. This work provides a feasible scheme for the pretreatment of tetracycline in water to meet the pretreatment requirements of special water.
Titanium xerogel coagulant (TXC) has been proved as a promising coagulant in water treatment. However, the turbidity removal efficiency of TXC is unsatisfactory as there is a considerable amount of dissolved organic matter (DOM). To overcome this shortage, a cationic flocculant, poly(diallyl dimethyl ammonium chloride) (PDADMAC), was composited into the TXC. With the removal of Escherichia coli ( E. coli ) and the residual turbidity as evaluation index, the composition of PDADMAC to TXC was proved to result in an enhanced resistance to DOM load. The resultant PDADMAC-TXC (P-T) composites had a good pH-resistance. In the pH range of 4.0–10.3, the required dose of P-T composites kept at a low level, whereas much higher doses were needed for the TXC. At pH 8.7, the minimum dose required to achieve a 90% E. coli removal from a 10 mg/L DOM solution was reduced from 70 mg/L TXC to 15 mg/L P-T composites. The improvements could be attributed to the three effects of PDADMAC in the P-T composites: strengthened charge neutralization for negatively charged E. coli , enhanced adsorption bridging through the polymer chains, and weakened complexation between organic matter and titanium due to the hydrophobic interactions between the aliphatic chains of PDADMAC and the hydrophobic segments of TXC. The work here provides a useful strategy for the fabrication of DOM-resistant coagulants to meet the requirements for some special kinds of water.
Chao-Hua Xue,Qian-Qian Tian,Shun-Tian Jia,Ling-Ling Zhao,Ya-Ru Ding,Hui-Gui Li,Qiu-Feng An
Stretchable superhydrophobic film was fabricated by casting silicone rubber polydimethylsiloxane (PDMS) on a SiO2 nanoparticle-decorated template and subsequent stripping. PDMS endowed the resulting surface with excellent flexibility and stretchability. The use of nanoparticles contributed to the sustained roughening of the surface, even under large strain, offering mechanically durable superhydrophobicity. The resulting composite film could maintain its superhydrophobicity (water contact angle ≈ 161° and sliding angle close to 0°) under a large stretching strain of up to 100% and could withstand 500 stretching–releasing cycles without losing its superhydrophobic properties. Furthermore, the obtained film was resistant to long term exposure to different pH solutions and ultraviolet light irradiation, as well as to manual destruction, sandpaper abrasion, and weight pressing.
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