Search

In this manuscript, a chitosan cross-linked zeolite molecular sieve (CTS/ZMS) was prepared and studied as adsorbent for nitrate ion from the ground water having low temperature below 10°C. Batch equilibration studies indicated that the prepared CTS/ZMS composite had good adsorption capacity (2.11 mg/g) from neutral water (pH = 7.0) under low temperature (9°C ± 1°C) which make it suitable for treatment of drinking water at low temperature. In batch equilibration method, 1.0 g of CTS/ZMS composite was able to remove 70.2% of nitrate ion from 100 mL of water containing 30 mg/L of nitrate ions and having a neutral pH of 7 when contacted for 420 min at a temperature of 9°C ± 1°C. Thermodynamic studies showed that the adsorption of nitrates was spontaneous, endothermic, and thermodynamically favourable. The kinetic studies indicated that the pseudo-second- order model fit the experimental data well (R2= 0.989), and it was also observed that adsorption isotherms can be well-described by Langmuir models (R2= 0.989). The physicochemical characteristics of the CTS/ZMS composites before and after the nitrate adsorption were demonstrated by Fourier-transform infrared spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy methods. When the solution pH value was lower than the pHPZC= 10.0, the surface active groups of the CTS/ZMS composites like –OH and –NH2were positively charged (OH2+, NH3+). Therefore, electrostatic attraction between NO3–and OH2+and/or NH3+led to the removal of nitrate from the contaminated water. Regeneration experiments showed the CTS/ZMS composites could be reused at least five times without any considerable loss of adsorption capacity by treating with Na2CO3.

In this work, earthed atomizing corona discharge (EACD) technique was used to dispose wastewater produced during the manufacture of styrene-butadiene rubber. The effects of discharge time, volume of H2O2(VH2O2), and concentration of FeSO4(CFeSO4) on turbidity (Tb), pH value, biochemical oxygen demand (BOD5), chemical oxygen demand (COD), and the biodegradability of styrene–butadiene rubber wastewater (SBRW) was investigated using the EACD technique treatment process. After a cumulative EACD treatment for 21 min (i.e., three discharge cycles), the COD and Tbvalues of SBRW both decreased by 67% (from 600.8 to 200.0 mg L–1for COD and from 106.0 to 35.0 NTU for Tb). The pH value remained unchanged, while the BOD5value initially increased as the discharge time increased and then reached equilibrium. The COD value decreased subsequently to 80.0 mg L–1after a cumulative EACD treatment of 21 min when FeSO4was added. Meanwhile, the total decrease in the efficiency of the COD value was about 86.7%. However, the results show that H2O2had no impact on decreasing the COD value or improving the biodegradability. Therefore, the addition of FeSO4had a positive effect on decreasing the COD value for SBRW by cooperating with the EACD technique.