Preparation and Adsorption Properties of Activated Carbon from Glutinous Rice Straw by KOH Method

[Objective] This study aimed to improve comprehensive utilization value of glutinous rice straw and to develop new raw material for preparation of activated carbon. [Method] Using potassium hydroxide as activator and glutinous rice straw as raw material, activated carbon was prepared. [Result] The optimum technological conditions for preparation of activated carbon from glutinous rice straw were as fol- lows： activator concentration of 2 mol/L, activation time of 60 min, activation tem- perature of 600 ℃ and carbonization temperature of 450℃. The adsorption values of methylene blue and iodine by activated carbon prepared from glutinous rico straw were 10.21 ml/0.1 g and 920.74 mg/g respectively under the optimal conditions. The quality of the prepared activated carbon met the grade two of water quality purifica- tion-using activated carbon quality standard. [Conclusion] This study will provide certain references for comprehensive utilization of glutinous rice straw and preparation of high-performance activated carbon.

Activated Carbon from Rice Husk with One-Step KOH Mechanical Mixing Activation as Adsorbent for Treating Phenolic Wastewater

This study investigates how large-surface-area biocarbons with high phenolic adsorption capacities can be obtained from cheap and abundant rice husk(RH).The RH is directly mixed with potassium hydroxide(KOH)and activated in a flowing N_(2) atmosphere,and the effects of the pyrolysis temperature and KOH to RH ratio on the structure of the obtained activated carbon adsorbents and their adsorption of p-nitrophenol and phenol are studied.The results show that the optimum pyrolysis temperature of RH is 750℃,whereby the highest surface area of 2047 m^(2)/g and best adsorption performance are obtained with a KOH to RH ratio of 3:1.Moreover,the obtained biocarbons achieve a maximum adsorption capacity of 175 mg/g for phenol and 430 mg/g for p-nitrophenol,which are higher than most previously reported data.

Adsorption of Phenol by Activated Carbon Prepared from Waste Rice Straw by Chemical Activation with (NH_4)_2HPO_4

Activated carbons,RS-1,RS-2,and RS-3,prepared from rice straw with(NH4)2HPO4 activation were used as adsorbents for removing phenols from aqueous solutions.The maximum adsorption capacities of phenol for RS-1,RS-2,and RS-3 were 163.9,172.9,and 200.0 mg/g,respectively.The equilibrium data were analyzed by the Langmuir,Freundlich,and Temkin models.It displayed that Langmuir isotherm fitted to the results best.The dimensionless parameter RL indicated the favorable nature of the adsorption of phenol.Otherwise,the kinetic rates were well explained by pseudo-second-order model.According to the results,activated carbon derived from waste rice straw can be a high-performance adsorbent for wastewater treatment.

Cost Effective Adsorption of Aluminium and Iron from Synthetic and Real Wastewater by Rice Hull Activated Carbon (RHAC)

The adsorption of aluminium(III) and iron(III) ions from their single and binary systems, by RHAC was investigated in a batch system. The activated carbon prepared from rice hulls was characterized by scanning electron microscopy and Fourier transformation infrared techniques. Batch adsorption experiments were performed under different operating conditions including pH (2 - 5), adsorbent dosage (0.5 - 2.0 g/l), initial ion concentration (5 - 100 mg/l), and contact time (30 - 240 min). The equilibrium time for maximum ions removal was found to be 180 min in single and binary ions systems. The kinetics of adsorption was evaluated using the pseudo-first order, pseudo-second order and Elovich kinetic models. The Langmuir, Freundlich and Temkin equilibrium models were applied to the adsorption experimental data. Real wastewater samples were collected from different locations to investigate the efficiency of rice hull activated carbon in treating real samples. The real wastewater samples were treated with the activated carbon prepared from rice hulls and a commercial activated carbon. The results showed that the activated carbon prepared in the present work was more efficient in the removal of aluminium and iron from real wastewater as compared to the commercial activated carbon which is more advantageous considering both economics and environmental parameters.

Effects of Carbon and Nitrogen Additions on Soil Microbial Biomass Carbon and Enzyme Activities Under Rice Straw Returning

The effects of different amounts of carbon and nitrogen sources on the soil microbial biomass carbon,dissolved organic carbon and related enzyme activities were studied by the simulation experiment of rice straw returning to the field,and the mechanism of the decomposition of rice straw returning to the field was discussed.Completely randomized experiment of the two factors of the three levels was designed,and a total of nine treatments of indoor soil incubation tests were conducted.Full amount of rice straw was applied to the soil in this simulation experiment and different amounts of brown sugar and urea were added in the three levels of 0(no carbon source and nitrogen source),1(low levels of carbon and nitrogen sources)and 2(high levels of carbon and nitrogen sources),respectively.The results showed that the addition of different amounts of carbon and nitrogen sources to the rice straw could increase the soil carbon content.Compared with T0N0,the microbial biomass carbon of T2N2 was increased significantly by 170.48%;the dissolved organic carbon content of T1N2 was significantly increased by 58.14%and the free humic acid carbon contents of T0N2,T1N1 and T2N0 were significantly increased by 56.16%and 45.55%and 47.80%,respectively;however,there were no significant differences among those of treatments at later incubation periods.The addition of different carbon and nitrogen sources could promote the soil enzyme activities.During the incubation period,all of the soil enzyme activities of adding sugar and urea were higher than those of T0N0 treatment.Therefore,the addition of different amounts of carbon and nitrogen sources to rice straw returning could improve soil microbial biomass carbon content,dissolved organic carbon and soil enzyme activities.

Rice Husk at a Glance:From Agro-Industrial to Modern Applications

Excessive waste production has led to the concept of a circular bioeconomy to deliver valuable by-products and improve environmental sustainability.The annual worldwide rice production accounts for more than 750 million tons of grain and 150 million tons of husk.Rice husk(RH)contains valuable biomaterials with extensive applications in various fields.The proportions of each component depend primarily on rice genotype,soil chemistry,and climatic conditions.RH and its derivatives,including ash,biochar,hydrochar,and activated carbon have been placed foreground of applications in agriculture and other industries.While the investigation on RH’s compositions,microstructures,and by-products has been done copiously,owing to its unique features,it is still an open-ended area with enormous scope for innovation,research,and technology.Here,we reviewed the latest applications of RH and its derivatives,including fuel and other energy resources,construction materials,pharmacy,medicine,and nanobiotechnology to keep this versatile biomaterial in the spotlight.

Analysis of graphene-like activated carbon derived from rice straw for application in supercapacitor

Activated carbons with large surface area, abundant microporosity and low cost are the most commonly used electrode materials for energy storage devices. However, activated carbons are conventionally made from fossil precursors, such as coal and petroleum, which are limited resources and easily aggregate large block in high temperature carbonization processes. In this novel work, we examined the use of rice straw as a potential alternative carbon source precursor for the production of graphene-like active carbon. A very slack activated carbon with ultra-thin two-dimensional （2D） layer structure was prepared by our proposed approach in this work, which includes a pre-treatment process and potassium hydroxide activation at high temperatures. The obtained active carbon derived from rice straw exhibited a capacitance of 255 Fig at 0.5 A/g, excellent rate capability, and long cycling capability （98% after 10,000 cycles）.

Single and Binary Dye Adsorption of Methylene Blue and Methyl Orange in Alcohol Aqueous Solution via Rice Husk Based Activated Carbon:Kinetics and Equilibrium Studies

The present work was mainly focused on the single and binary adsorption of methylene blue(MB)and methyl orange(MO)from alcohol aqueous solution over rice husk based activated carbon(RHAC).The study of single dye adsorption equilibrium experiments found that the Langmuir adsorption model was consistent with the adsorption behavior of RHAC on MB and MO,indicating that it was a single layer adsorption.The adsorption behavior con-formed to the pscudo-second-order kinetic model.The binary dye adsorption experiments showed that the Lang-muir-Freundlich model could be applied to describe the adsorption behavior of RHAC on MB and MO.Comparation with the single dye system,the adsorption capacity on the binary dye system was larger,and there was"competitive adsorption"and"synergistic adsorption"effects existed.Meanwhile,the pseudo-second-order kinetic model also fit for the binary dye adsorption behavior.

Removal of Cr(VI)from aqueous solution by Rice-husk-based activated carbon prepared by Dual-mode heating method

Rice husk-based activated carbon was prepared with the help of zinc chloride using microwave and electrical dual-mode heating.The pore characteristics and chemical properties of rice husk-based activated carbon(RH-AC)were characterized by BET,XRD,Raman spectra,FTIR and pHIEP(pH of isoelectric point).The specific surface area of RH-AC is 1719.32 m^(2)/g with a total pore volume of 1.05 cm^(3)/g.The performance of RH-AC for removing Cr(VI)from aqueous solution was examined considering the variation of the contact time(0-120 min),pH value(2.0-9.0),adsorbent dose(0.5-3.0 g/L),initial concentration(28-145 mg/L)and solvent temperature(15-45℃).The ideal pH for Cr(VI)removal is between 2.0 and 3.0 with the equilibrium time of 90 min,achieving the maximum adsorption capacity of 56.82 mg/g with the pH of 3.0.Comparable study on the established kinetic models and isotherms to simulate the removal of Cr(VI)by RH-AC was carried out to sort out the inherent mechanism of the absorption.Reasonable agreements could be obtained by the pseudo-second-order kinetic model and Langmuir,Freundlich and Tempkin isothermal models.Results from Body model simulation suggest that external mass transfer was the essential cause for rate-controlling in the adsorption process of Cr(VI).

稻壳一步活化联产白炭黑和超级电容器用活性炭的研究

以稻壳(husk rice,HR)为生物质碳源,碳酸钾(K2CO3)为活化剂,通过一步活化的方法同时制备活性炭与白炭黑,研究工艺参数碱炭比、活化温度等参数以及碱煮过程对活性炭物化特性和电化学性能的影响。结果表明,碳酸钾作为活化剂对活性炭蚀刻造孔能力优秀,可以大幅改善活性炭的孔隙结构;碱煮对于活性炭影响不大,同时可以联产制备高品质的白炭黑。最佳的工艺参数下制得的A-RHAC,碘吸附值达1282.9 mg/g,亚甲基蓝吸附值达440.4 mg/g,比表面积达1410.9 m^(2)/g,介孔率达30.28%,应用于超级电容器中,A-RHAC的比电容可达177.454 F/g,充放电循环5000次后的比电容保持率达到95.11%,20000次循环后仍达到75.86%,倍率性能和循环稳定性优秀。

Multiple Functional Biomass-Derived Activated Carbon Materials for Aqueous Supercapacitors, Lithium-Ion Capacitors and Lithium-Sulfur Batteries

Biomass-derived activated carbon electrode materials have been synthesized by carbonization and KOH activa- tion processes from an agriculture waste - rice husk, composed of organic compound and silica. The surface area of activated carbon reached 1098.1 m2/g mainly including mesopores and macropores due to the template effect of sil- ica in rice husk. Owing to the existence of mesopores and macropores, the as-obtained activated carbon materials can be used in aqueous supercapacitors, lithium-ion （Li-ion） capacitors and lithium-sulfur （Li-S） batteries. In KOH electrolyte, fast rate performance （as high as 2 V/s） was obtained due to the existence of ideal electrical double layer capacitance. In organic electrolyte, high voltage （2.5 V） was achieved. Activated carbon electrode for Li-ion capac- itor also showed capacity of 17 mAh/g at 100 mA/g with the high voltage range of 2.5 V. The capacities of sul- fur-activated carbon in Li-S batteries were 1230 and 970 mAh/g at the current densities of 0.1 and 0.2 C. The pre- sent results showed that activated carbon materials with mesopores were good host to immobilize polysulfides.

化肥减量配施生物有机肥对水稻产量、土壤结构和土壤固碳增汇能力的影响

为了探究减氮配施生物有机肥对水稻产量、土壤结构和土壤固碳增汇能力的影响,分别设置无氮肥对照(CK)、常规施肥(T1)、减氮10%配施生物有机肥(T2)和减氮20%配施生物有机肥(T3)4个处理。结果表明,与T1处理相比,减氮配施生物有机肥(T2和T3)处理对水稻产量和稻米品质没有显著影响,但是显著增加了土壤有机质含量和水稻氮利用效率。与T1处理相比,T2和T3处理显著增加了≥0.25 nm土壤团聚体(大团聚体)的比例,降低了<0.25 nm土壤团聚体(小团聚体)的比例,并显著增加了不同粒径团聚体中的有机质含量。同时,T2和T3处理显著增加了土壤中颗粒有机碳的含量和比例,增加了矿物结合态有机碳的含量,但是降低了其在土壤中的比例。T2和T3处理同时增加了土壤中脲酶和蔗糖酶活性、微生物生物量碳和氮含量、细菌和固碳菌的丰度。因此,水稻生产中可通过施加生物有机肥来减少氮肥施加、维持水稻产量和保持土壤地力水平。

由稻壳制备高比表面积活性炭

以稻壳为原料 ,KOH为活化剂制备了高比表面积活性炭 ,其比表面积超过 30 0 0 m2 /g,且孔径均一 。

耕作措施对长期免耕双季稻田土壤碳库的影响

针对南方稻田长期免耕存在的主要问题，本研究选择湖南省双季稻区连续7年免耕稻田，进行了不同耕作措施对土壤的总有机碳、活性有机碳的变化情况及其对土壤碳库影响的研究，以期为建立合理的轮耕周期提供理论依据。结果表明：0～20cm平均总有机碳和活性有机碳含量均为旋耕〉连续免耕〉翻耕。与连续免耕相比，旋耕有利于提高土壤活性有机碳含量（比连续免耕提高了5．08％），翻耕则会促进土壤活性有机碳分解（比连续免耕降低了2．73％）。晚稻收获时0～20cm平均碳库管理指数也表现为旋耕〉连续免耕〉翻耕，其中翻耕使碳库管理指数整体上显著降低（比连续免耕降低了21．7％）；旋耕略有提高（比连续免耕提高了3．9％），但未达到显著水平（P〈0．05）。总之，与连续免耕相比，翻耕可促进土壤活性有机碳分解，进而显著降低碳库管理指数；但旋耕差异不显著（P〈0．05）。

由稻壳灰制备活性炭的工艺及应用研究

对利用稻壳灰与碱反应制备活性炭、水玻璃及白炭黑的工艺条件进行了研究 ,通过单因素实验和正交实验 ,筛选出了反应的最佳工艺条件 :稻壳灰与KOH配比为 1∶0 .2 2 ,反应时间 4h ,反应压力 0 .6MPa。在此条件下二氧化硅的溶出率为 95 % ,硅酸钾的模数为 2 .8～ 3.2 ,白炭黑的白度在 90 %以上。提出了提高产品质量的有效方法 ,对产品的应用性能也作了分析。实验结果表明采用炭化稻壳为原料生产的活性炭、白炭黑及水玻璃质量完全达到了相应的国家标准 。

磷酸活化稻秆制备中孔活性炭的研究

以稻秆为原料,通过磷酸法活化制备得到了中孔活性炭,并采用氮气吸附、元素分析和扫描电镜对其进行了表征分析。实验结果表明:稻秆制备活性炭的工艺条件为10 g稻秆,浸渍比3∶1(质量比),在140℃下预活化60 min,活化温度450℃,活化时间60 min。在此条件下制备得到的活性炭得率为25%,亚甲基蓝吸附值215 mg/g,碘吸附值835 mg/g,A法焦糖值110%,灰分3.03%,其比表面积为967.7 m2/g,总孔容为1.12 cm3/g,平均孔径为4.6 nm,中孔率可以达到84.8%。

碱炭比及活化温度对稻壳活性炭极微孔的影响

采用N2吸附、CO2吸附和热重红外联用等技术手段,考察了在KOH活化稻壳炭的过程中碱炭比和活化温度对活性炭极微孔的影响。结果表明：在不同碱炭比（0.6︰1~3︰1）和活化温度（640~780℃）下制备的稻壳活性炭,极微孔主要分布在0.42~0.70 nm。当碱炭比增加时,极微孔孔容先增大后减小;而当活化温度升高时,极微孔孔容呈降低趋势。极微孔率随碱炭比或活化温度的升高而单调递减。在活化温度为640℃、碱炭比为1：1时,可得极微孔孔容为0.149 m L/g、极微孔率达36.3%的微孔活性炭。活性炭的极微孔孔容与其在104 Pa时的CO2吸附量高度线性相关。

微波辐照稻杆制造活性炭

研究了微波辐照经氯化锌浸渍的稻杆制造活性炭。实验结果表明 ,经微波辐照 8min ,所得活性炭的亚甲基蓝脱色力为 15mL/ 0 .1g ,为国家标准一级品 (LY 2 16- 79)的 1 2 5倍 ,时间仅为传统方法的 1/ 45。

稻草秸秆基活性炭对苯酚和亚甲基蓝的吸附性能研究

[目的]研究稻草秸秆基活性炭对苯酚和亚甲基蓝的吸附性能。[方法]选用(NH4)2HPO4为活化剂,利用农业废弃物——稻草秸秆为原料,通过化学活化法制得3种稻草秸秆基活性炭RN-1、RN-2和RN-3。通过N2吸附-脱附等温曲线和Boehm滴定法对其表面的物理和化学性质进行表征。[结果]结果表明,预氧化处理不仅会改变活性炭表面含氧基团的含量,也对其比表面积有影响。将活性炭应用于水中的亚甲基蓝和苯酚吸附,活性炭吸附苯酚和亚甲基蓝符合拟二级动力学方程。RN-3(187.7 mg/g)具有最大的苯酚吸附量,对亚甲基蓝的最大吸附量RN-3(166.35 mg/g)和RN-1(161.00 mg/g)相近。说明活性炭对亚甲基蓝的吸附受比表面积和含氧基团的共同影响,含氧基团量的升高不利于其对亚甲基蓝的吸附。[结论]该研究为稻草秸秆的合理利用提供科学依据,以达到以废制废的目的。

稻壳制活性炭及其对污水中铬的吸附能力研究

研究了以稻壳为原料用磷酸活化法制备粉状活性炭的条件,并探讨了稻壳活性炭对水中铬离子的吸附性能。结果表明废弃稻壳在氮气保护下,以每分钟升温10℃的速率加热到400℃进行预炭化,再在800℃条件下活化所制备的活性炭对废水中重金属铬离子具有较强的吸附性能。这为稻壳的综合利用、提高农副产品的价值及解决环境污染提供了一条途径。