酸及螯合预处理对光催化漂白的影响

通过原子吸收光谱分析知道,未漂浆经过硫酸和乙二胺四乙酸(EDTA)螯合预处理后,金属离子Mg2+、Mn2+、Fe3+、Zn2+、Cu2+的含量有不同程度的降低,其中酸预处理时Cu2+、Mg2+的去除率最高,螯合预处理时Fe3+、Zn2+的去除率最高,并且当硫酸和鳌合剂的加入量分别为1.5%和0.6%时,金属离子的去除量较高。经过酸和螯合预处理后,纸浆的白度分别提高了3.8%ISO-5.0%ISO和4.30%ISO-5.2%ISO,纸浆的硬度下降率分别为6.5%-9.6%和5.3%-10%左右,并且当酸和鳌合剂的加入量分别为1.0%和0.6%时,纸浆的白度提高最显著,硬度下降最大,黏度下降很小。通过对预处理前后的纸浆进行光催化漂后的对比研究发现,酸预处理使纸浆的白度降低了2.3%ISO-3.5%ISO,硬度和黏度各自的降低率相近;而鳌合预处理使纸浆的白度提高了3%ISO左右,硬度降低率提高6%左右,黏度却保持较好。

Effects of Acid and Chelating Pretreatment on Photocatalysis Bleaching

As the unbleached pulp is acidified with sulfuric acid or chelated with ethylenediamine tetraacetate(EDTA),the contents of metal ion Mg2+,Mn2+,Fe3+,Zn2+ and Cu2+ are reduced in different degrees by atomic absorption spectrometry analyzing,and the removal rate of Cu2+ and Mg2+ with acid pretreatment is the highest,but the removal rate of Fe3+ and Zn2+ with EDTA pretreatment is the highest.In addition,when the addition amount of sulfuric acid or chelating agent are 1.5% and 0.6% respectively,the removal rate of metal ions are higher.After acid or chelating pretreatment,the brightnesses of pulps are increased respectively 3.8%ISO~5%ISO and 4.30%ISO~5.2%ISO,and the reduction rates of permanganate number are 6.5%~9.6% and 5.3%~10% respectively.And when the addition amount of acid and chelating agent are 1.0% and 0.6% respectively,the brightness of pulp is improved significantly,the permanganate number is declined maximally,but the viscosity is fallen slightly.The pulps with and without pretreatment are bleached by photocatalysis,the results show that after acid pretreatment the brightness of pulp is reduced 2.3%ISO~3.5%ISO,the reduction rate of permanganate number and viscosity is similar.And after chelating pretreatment the brightness of pulp is increased 3%ISO,the reduction rate of permanganate number is increased 6%,but the viscosity is kept well.