Pretreatment of wastepaper and pulp mill sludge by aqueous ammonia and hydrogen peroxide

Pretreatment of two different softwood-based lignocellulosic wastes (newsprint and Kraft pulp mill sludge) was investigated. Pretreatment was done by aqueous ammonia and hydrogen peroxide (H₂O₂), two delignifying reagents that are environmentally benign. Three different treatment schemes were employed: aqueous ammonia alone (ammonia recycled percolation [ARP]), mixed stream of aqueous ammonia and H₂O₂ and successive treatment with H₂O₂ and aqueous ammonia. In all cases there was a substantial degree of delignification ranging from 30 to 50%. About half of the hemicellulose sugars were dissolved into the process effluent. Retention of cellulose after pretreatment varied from 85 to 100% for newspaper feedstock and from 77 to 85% for the pulp mill sludge. After treatment with aqueous ammonia alone (ARP), the digestibility of newspaper and the pulp mill sludge was improved only by 5% (from 40 to 45% for the former and from 68 to 73% for the latter), despite a substantial degree of delignification occurring after the ARP process. The lign in content thus did not correlate with the digestibility for these substrates. Simultaneous treatment with H₂O₂ and aqueous ammonia did not bring about any significant improvement in the digestibility over that of the ARP. A succcessive treatment by H₂O₂ and ARP showed the most promise because it improved the digestibility of the newspaper from 41 to 75%, a level comparable to that of α-cellulose.     

Enzymatic digestibility of used newspaper treated with aqueous ammonia-hydrogen peroxide solution

Wastepaper constitutes approximately half of municipal solid waste, making it a potential source of bioenergy. Newspaper was pretreated with an ammonia-hydrogen peroxide (H₂O₂) mixture in a shaking bath from room temperature to 80°C, and then its enzymatic digestibility was measured. A significant amount of ink was removed from the newspaper slurry by the reciprocating movement of the shaking bath. In addition, the ammonia-H₂O₂ significantly swelled the substrate, thereby greatly increasing its susceptibility to enzymatic digestion. After pretreating the newspaper with conditions of 40°C, 3 h, 130 strokes/min, and 4 wt% ammonia-2 wt% H₂O₂, the enzymatic digestibility was almost 90% of theoretical, or about 25% higher than that of untreated substrate. Digestibility was also investigated as a function of ammonia concentration, H₂O₂ concentration, shaking speed, pretreatment temperature, and time.     

中国报纸出版业区域发展不均衡性的计量分析

依我国各省(市、自治区)报纸种数、报纸总印数和报纸总印张数等三个指标1986-2006年的数据,构建这一时期各指标相对熵的时间序列。应用ADF检验求时间序列单整阶数并做出分析,应用方向数据统计探讨报纸总印张数相对熵的周期变化。     

顶空/气相色谱-质谱法同时测定报纸中14种溶剂残留

建立了同时测定报纸中14种溶剂残留量的顶空/气相色谱-质谱分析法。采用顶空气相色谱技术,以毛细管柱(Agilent HP-INNOWAX,60 m×250μm,0.25μm)分离,选择离子监测模式(SIM)下进行质谱检测。在优化的顶空/气相色谱-质谱分析条件下,14种溶剂残留在2~20μg范围内线性关系良好,相关系数均不小于0.995;方法的定量下限(S/N=10)均小于0.01 mg/m2。加标水平为3.97~16.28μg时,待测物的平均回收率为86.6%~101.8%,相对标准偏差(RSD,n=6)均不高于6.8%。本方法快速、准确、灵敏,适用于报纸中溶剂残留的测定。     

Enhancement of the enzymatic digestibility of waste newspaper using tween

Methods of increasing the enzymatic digestibility of waste newspaper by adding Tween (TW)-20 and 80 surfactants were investigated. Tween-series surfactants were selected because these surfactants increase cellulase activity during enzymatic hydrolysis and do not inhibit cell growth in downstream fermentation processes. When surfactant was used in a pretreatment, a benefic effect was expected in the enzymatic hydrolysis stage owing to surfactant carry-over from the pretreatment stage immediately upstream of the hydrolysis. However, because it was necessary to wash the pretreated substrate with water to remove inhibitors produced during pretreatment, no added benefit was obtained. When surfactant was used in the pretreatment only, it was found that it had a marked effect on digestibility and that this effect was higher at lower enzyme loadings. Also, TW-80 was found to be more effective than TW-20, and the addition of enzyme and TW-80 to substrate at the beginning of enzyme reaction was found to most effectively increase digestibility. When TW-80 was added into either the pretreatment stage or the hydrolysis stage the digestibilities of untreated sample increased by approx 40%, whereas an increase of only 45% was observed when TW-80 was added to both stages. These results show that the addition of surfactant to either the pretreatment or the enzymatic hydrolysis stage is sufficient to increase digestibility.     

Enhancement of enzymatic digestibility of recycled newspaper by addition of surfactant in ammonia-hydrogen peroxide pretreatment

The effect of surfactant on enzymatic digestibility was investigated during the pretreatment stage. Newspaper was pretreated with an ammonia-hydrogen peroxide mixture on a shaking bath at 40°C and 130 strokes/min for 3 h. Two kinds of nonionic surfactants, NP series and Tween series, were utilized. The effect of hydrophile-lipophile balance (HLB) value of both series surfactants on digestibility was found to be negligible, even though de-inking efficiency was improved as HLB value was increased. The effect of surfactant loading on digestibility was small, below 0.5 wt%, and negligible above 0.5 wt% at 60 international filter paper units (IFPU). The percentage improvement in digestibility increased as enzyme loading decreased. Digestibility of NP-5-added sample relative to control sample, increased significantly at an enzyme loading <60 IFPU, i.e., 19 and 13% at 15 and 30 IFPU, respectively. Such an increase in digestibility was not explained clearly from the experimental results. It was also found that ink removal before enzymatic hydrolysis is very important to enhance digestibility.