Recovery of nutrients from the liquid fraction of digestate: Use of enriched zeolite and biochar as nitrogen fertilizers

The liquid fraction after liquid/solid separation of biogas digestate has a high potential as a fertilizer due to its high nutrient concentration. However, the direct application of digestate in agricultural fields results in practical problems due to its voluminous nature. One solution to this could be to concentrate nutrients onto sorbents such as biochar or zeolites, which can subsequently be used as a fertilizer. This study investigated the ability of biochar and zeolite ‘clinoptilolite' enriched with digestate nutrients to supply nitrogen (N) when used as a fertilizer. A pot experiment with ryegrass was conducted to test the effect of a nutrient‐enriched biochar and clinoptilolite by determining plant biomass growth and N uptake. This included untreated biochar and clinoptilolite as controls and two levels of N application (15 and 45 mg N per pot) each at two initial loading ratios (low and high). Nutrient‐enriched biochar and clinoptilolite increased plant biomass yield (up to 1.02 and 2.39 g per pot) and N uptake (up to 11.23 and 39.94 mg N per pot) compared to the untreated sorbents treatments. Initial loading ratio had a significant effect on plant biomass response and apparent N recovery (ANR) for enriched clinoptilolite, and lower initial loading ratio improved plant growth. In contrast to clinoptilolite, higher initial loading ratio resulted in higher ANR. In conclusion, our results reveal that N released from enriched clinoptilolite and biochar could be taken up by the plants, clinoptilolite performed more effectively than biochar, and initial loading ratio affected the performance of the sorbents when used as a fertilizer.     

Ca—K型斜发沸石对盐化土壤速效钾的影响

采用微型盆栽和大田试验,研究了赤城产Ｃａ－Ｋ型斜发沸石对盐化土壤有效钾的影响,以及斜发沸石在盐化土壤的供钾能力和后效。结果表明：土壤速效钾含量随沸石施用量的增加而增加;土壤中施入铵态氮肥能促进沸石中钾的释出;将沸石一次 施入盐化潮土中,在４ａ内土壤速效钾可增加５％～２５％。显然,Ｃａ－Ｋ型斜发沸石对土壤钾的供应具有调控作用。     

斜发沸石添加水平对育肥期苏淮猪生长性能、屠宰性能和肉品质的影响

本试验研究基础日粮中添加不同水平的斜发沸石对育肥期苏淮猪生长性能、肉品质的影响,旨在获得苏淮猪育肥期斜发沸石的适宜添加量。选择体重相近(50 kg左右)、健康的苏淮阉公猪40头,随机分为对照组、试验Ⅰ组、试验Ⅱ组、试验Ⅲ组共4个处理组,每组10头。预试期10 d,所有猪自由采食对照组基础日粮;正试期64 d,对照组饲喂基础日粮,试验Ⅰ至Ⅲ组分别在基础日粮中添加0.5%、1.0%和2.0%的斜发沸石。于试验结束屠宰全部试验猪,用于屠宰测定和肉质检测。结果表明:1)第1阶段(体重56~68 kg)和第2阶段(体重83~98 kg),终末体重、平均日增重、料重比均无显著差异;但斜发沸石水平对第1阶段和第2阶段平均日采食量影响显著(P<0.05)并呈线性(P=0.02,P=0.047)二次方升高趋势(P=0.01)。2)对照组、试验Ⅰ组、Ⅱ组和Ⅲ组苏淮猪的生长曲线拐点分别是:第50.26天86.06 kg、第40.22天87.15 kg、第38.27天89.69 kg和第45.98天89.02 kg;最大日增重分别是0.702、0.743、0.814和0.855 kg/d,说明在饲料中添加斜发沸石后,可延长育肥猪到达生长曲线拐点体重。3)斜发沸石水平对眼肌面积和肌内脂肪影响显著(P<0.05),眼肌面积随斜发沸石添加水平的升高,呈二次方(P=0.01)变化;肌内脂肪呈线性(P=0.01),二次方(P=0.03)升高;胴体重和系水力分别随斜发沸石添加水平的升高,呈线性(P=0.07,P=0.09)升高趋势。试验表明:苏淮育肥猪采食量、胴体重和肌内脂肪随日粮斜发沸石添加水平增加呈线性升高,系水力呈线性升高趋势,但眼肌面积随斜发沸石添加水平的升高,呈二次方变化,先升高后降低。因此,添加2%斜发沸石有利于采食量、胴体重和肌内脂升高,有助于系水力降低;但从增加眼肌面积的角度考虑,斜发沸石的适宜添加比例为1%。     

天然沸石作为离子交换肥料的研究——Ⅱ斜发沸石对磷矿石的溶解及对土壤有效磷的影响

在实验室条件下,研究了斜发沸石(Cp)对三种不同磷矿石的溶解作用及对土壤有效磷的影响。结果表明:斜发沸石上所吸附的阳离子在不同程度上都有增加磷矿石的水溶性磷的作用,其增溶量因矿石种类而异。而且不同斜发沸石还因其所吸附的阳离子种类不同,对水溶性磷的增溶效果也有极大差别。各种吸附离子对水溶性磷的增溶效果依次为:H.Al-Cp>Na-Cp>NH_4-Cp>K-Cp>Ncp>Mg-Cp>Ba-Cp>Ca-Cp.但就磷矿石中酸性枸溶性磷的溶解能力而言,同样用斜发沸石处理,其对所试三种磷矿石种类影响均不大。这些事实说明斜发沸石对磷矿石中磷的增效机制,主要是通过斜发沸石上的吸附性阳离子和磷矿石中Ca~(2+)离子的直接接触交换或溶液交换的结果。另一方面,也可以根据不同吸附离子对Ca~(2+)离子的选择交换力大小的序列而加以解释。此外磷矿石本身的化学组成及结晶构造等特征不同,也是产生上述磷的增溶效果不等的原因。中性或微酸性水稻土施用斜发沸石能增加土壤有效磷含量(Bray-Ⅰ磷),并使其固磷能力有所下降。而酸性较强的土壤则因有次生固磷作用,有效磷含量没有增加。     

天然沸石对磷、钾在红壤中迁移影响的室内模拟研究

为了寻求提高磷钾肥利用率的途径，该文采用恒温振荡试验初步研究了天然沸石对水溶性磷、钾在红壤中向无效态转化的影响。结果表明：添加沸石降低了水溶性磷、钾含量，增加了解吸钾量；解吸磷和有效磷在磷酸二氢钾低水平时比对照均降低；在磷酸二氢钾高水平时，前者降低而后者增加了9.6%～32.2%。在富磷的红壤中添加沸石提高了有效磷含量，降低了磷损失的可能性；沸石在红壤中作为钾库和钾源，可调节土壤钾水平。     

磁性斜发沸石对溶液中Pb2+的吸附性能

利用磁性斜发沸石作吸附剂,考察了含背景电解质溶液初始pH、吸附剂投加量、Pb2+初始浓度、吸附时间等对其吸附Pb2+的影响,通过动力学模型和等温吸附模型探讨了磁性斜发沸石吸附Pb2+可能的作用机制.结果表明,磁性斜发沸石能够有效去除水体中的Pb2+,最大吸容附量达136.1 mg/g.磁性斜发沸石对Pb2+的吸附平衡时间为48h,溶液pH =6.0左右时,吸附剂投加量增大有利于Pb2+的去除;随着溶液中NaNO3背景电解质浓度增大,磁性斜发沸石对Pb2+的吸附量显著降低;吸附行为符合准二级动力学模型及Langmuir等温吸附模型.推测磁性斜发沸石对Pb2+的吸附既有物理吸附又有化学吸附.     

斜发沸石的毒性试验研究

为了开发新的饲料添加剂，阐明其限量标准和安全性，本试验首次对延边经济研究所提供的斜发沸进行了急性毒性、蓄积毒性及毓毒性试验研究，结果表明：急性毒性试验LD50＞20g/kg，表明斜发沸石属实际无毒性物质；经20d蓄积毒性试验，小鼠均未见消瘦和死亡，表明斜发沸石蓄积毒性作用；经繁殖试验证明，2.5％剂量组小鼠的出生存活率、体重、哺育存活率和增重都明显高于其它试验组及对照组，但当大于5.0%剂量时，则对动物不利。     

紫外光下,卤离子对TiO_2/斜发沸石光降解酸性桃红的影响

本文研究了添加Cl-和I-后,在紫外光照射下,对TiO2/斜发沸石和P25光催化降解酸性桃红的影响.紫外可见光谱结果表明对于TiO2/斜发沸石催化剂,添加Cl-和I-后,反应速率变小;对于P25催化剂,添加Cl-后,反应速率变大,添加I-后,反应速率变小.COD测试结果表明对TiO2/斜发沸石和P25,添加I-后,矿化速率均变慢.还进行了H2O2和ESR(电子顺磁共振,Electron Spin Resonance)测试,与反应机理相联系,解释了反应现象.TiO2/斜发沸石寿命实验结果表明该催化剂循环使用4次以上,催化剂活性才开始下降,而且它更加易于从分散体系中沉降分离,是1个有应用前途的催化剂.     

Zinc‐bearing zeolite clinoptilolite improves tissue zinc accumulation in laying hens by enhancing zinc transporter gene mRNA abundance

A study was conducted to investigate effects of zinc‐bearing zeolite clinoptilolite (ZnCP), as an alternative for zinc sulfate (ZnSO₄), on laying performance, tissue Zn accumulation and Zn transporter genes expression in laying hens. Hy‐Line Brown laying hens were allocated to three treatments, each of which had six replicates with 15 hens per replicate, receiving basal diet supplemented with ZnSO₄ (control, 80 mg Zn/kg diet), 0.23% ZnCP (40.25 mg Zn/kg diet) and 0.46% ZnCP (80.50 mg Zn/kg diet) for 8 weeks, respectively. Compared with control, hens fed diet containing 0.23% ZnCP had similar Zn content in measured tissues (P > 0.05). A higher ZnCP inclusion (0.46%) enhanced Zn accumulation in liver (P < 0.05) and pancreas (P < 0.05). In addition, ZnCP inclusion increased blood iron (Fe) content (P < 0.05). ZnCP supplementation enhanced jejunal metallothionein‐4 (MT‐4) messenger RNA (mRNA) abundance (P < 0.05). ZnCP inclusion at a higher level (0.46%) increased mRNA expression of MT‐4 in pancreas (P < 0.05) and zinc transporter‐1 (ZnT‐1) in jejunum (P < 0.05). The highest ZnT‐2 mRNA abundance in jejunum was found in hens fed 0.23% ZnCP inclusion diet (P < 0.05). The results indicated that ZnCP reached a higher bioavailability as compared with ZnSO₄ as evidenced by enhanced tissue Zn accumulation and Zn transporter genes expression.     

Clinoptilolite Zeolite Influence on Nitrogen in a Manure-Amended Sandy Agricultural Soil

Zeolite minerals may improve nitrogen availability to plants in soil and reduce losses to the environment. A study was conducted to determine the influence of clinoptilolite (CL) on nitrogen (N) mineralization from solid dairy manure (224 kg N ha^?1) in a sandy soil. Clinoptilolite was added to soil at six rates (0 to 44.8 Mg CL ha^?1), each sampled during 11 sampling dates over a year. Over time, nitrate (NO₃)-N increased, ammonium (NH₄)-N decreased, but total inorganic N increased. Clinoptilolite did not influence the nitrification rates of initial manure NH₄-N or mineralization of organic N (ON) over time. It is possible that adsorption of manure-derived potassium (K) outcompeted the NH₄-N for CL exchange sites. The ON concentration was constant up to 84 days and then decreased by approximately 18% over the remaining time of the study across all treatments. Clinoptilolite use in this sandy soil did not alter mineralization of N from dairy manure.