玉米芯生物炭对含盐污水中氨氮的吸附特性

以玉米芯为原料制备生物炭,并采用"盐酸+超声波"改性,研究了其对含盐污水中氨氮的吸附特性。结果表明,改性玉米芯生物炭的比表面积和酸性含氧官能团含量较改性前分别提高了7.5、18.2倍,在氨氮初始质量浓度为40 mg/L、盐度为0.45%、p H值为5.0、投加量为2.5 g时,对氨氮的吸附率可达79.4%。改性玉米芯生物炭在含盐条件下对氨氮的吸附过程更符合准二级动力学模型和Langmuir模型,理论最大吸附量为2.538 2~2.842 6 mg/g,显著高于改性前。热力学分析表明,玉米芯生物炭对含盐污水中氨氮的吸附主要为物理吸附,且是自发、放热及熵增加的过程。以HCl为解吸剂,改性前后玉米芯生物炭的最佳吸附-解吸循环次数分别为3、7次,再生后对氨氮的平衡吸附量分别为解吸前的85.1%、93.8%。

Study on the adsorption feature of ammonium nitrogen in the salt-laden sewage by the corn cob biochar

This paper attempts to introduce our experimental innovation in preparing a modified adsorbent by the corn cob biochar(CCB) with hydrochloric acid and ultrasonic technology,trying to prepare it for adsorbing the ammonium nitrogen in treating the salt-laden sewage.To achieve the said purpose,we have made exploration of the structure and properties of CCB pre-&-post the modification through elemental analysis,Boehm titration,BET-N2 and the electronic microscopy scanning.At the same time,we have also made an investigation of the effects of different adsorptive parameters,such as the salinity degree,the pH value and the adsorbent dosage through batch experiments in hoping to optimize the research conditions.In addition,we have also taken the hydrochloric acid,nitric acid and the sulfuric acid as the desorption agents to trace the regeneration performance of CCB.The results of the above experiments can be shown as follows:the specific surface area and the acid oxygen-laden functional groups of the modified CCB have been increased by 7.5 and 18.2 times,respectively,as compared with the unmodified CCB counterpart,which helps to lay a basis for improving the ammonium nitrogen adsorption function.Furthermore,the modified CCB can help to increase the ammonium nitrogen removal rate by 79.4％ on the condition that the initial ammonium nitrogen concentration is 40 mg/L,whereas the salinity is 0.45％,pH value is 5.0 with the adsorbent dosage being 2.5 g.Moreover,the adsorption process of the modified CCB has been found following the kinetic model of the pseudo-second-order with a determinant coefficient of 0.985 8 and a theoretical equilibrium adsorption capacity of 1.310 3 mg/g.Its isothermal adsorption process can also be well described by the Langmuir model in its theoretical maximum adsorption capacity from 2.538 2 mg/g to 2.842 6 mg/g,which is significantly higher than that before being modified.Such a thermodynamic(△G(⊙),△H(⊙),△S(⊙)) analysis shows that the ammonium nitrogen adsorption in the salt-laden sewage by CCB can both be attributed to physical one and exothermic one with some spontaneous feature and the increased entropy one.And,finally,it is possible to choose the hydrochloric acid as the optimal desorption agent of ammonium nitrogen for CCBN,600 and CCBM,600,with their maximal adsorption-desorption cycle being 3 and 7 times,respectively.At the same time,the equilibrium adsorption capacity of ammonium nitrogen for the regenerated CCBN,600 and CCBM,600 has been made to reach 85.1％ and 93.8％ of the adsorption capacity before the given desorption.