Enhanced copper recovery from low grade copper sulfide ores through bioleaching using residues produced by fermentation of agricultural wastes

Effects of residues produced by agricultural wastes fermentation(AWF)on low grade copper sulfide ores bioleaching,copper recovery,and microbial community were investigated.The results indicated that adding appropriate bulk of AWF made contributions to low grade copper sulfide ores bioleaching,which may be mainly realized through reducing the passivation layer formed by Fe3+hydrolysis.Improved copper recovery(78.35%)and bacteria concentration(9.56×10^(7)cells·mL^(−1))were yielded in the presence of 5 g·L^(−1)AWF.The result of 16S rDNA analysis demonstrated that microbial community was differentiated by adding AWF.Bacteria proportion,such as Acidithiobacillus ferrooxidans,Moraxella osloensis,and Lactobacillus acetotolerans changed distinctly.Great difference between samples was showed according to beta diversity index,and the maximum value reached 0.375.Acidithiobacillus ferrooxidans accounted for the highest proportion throughout the bioleaching process,and that of sample in the presence of 5 g·L^(−) AWF reached 28.63%.The results should show reference to application of agricultural wastes and low grade copper sulfide ores.

Preparation of Dicarboxyl Cellulose Nanocrystals from Agricultural Wastes by Sequential Periodate-Chlorite Oxidation

Agricultural waste straw is the renewable resource with the highest annual yield in the world.In value-added applications of agricultural waste,dicarboxyl cellulose nanocrystals(DCCs)are prepared from rice,wheat,and corn straw by sequential periodate-chlorite oxidation.In this study,DCCs from rice,wheat,and corn straw were characterized by transmission electron microscopy(TEM),Fourier transform infrared spectrometer,X-ray diffractometer(XRD),and thermal gravimetric analysis(TGA).The carboxyl content of the DCCs was also investigated.XRD results show that the crystallinity index decreased after sequential periodate-chlorite oxidation;however,the cellulose I structure was maintained.TEM results show that rod-shaped DCCs with an average length and width of 287.0 nm and 9.9 nm,respectively,were successfully prepared by sequential periodate-chlorite oxidation.The carboxyl content of the DCCs was around 3.9 mmol/g,and not affected by the type of straw.Experiments to study the removal of copper ions in aqueous medium were performed with the prepared DCCs.The adsorption capacities of copper ions were 131,162,and 144 mg/g for DCCs prepared from rice,wheat,and corn straws,respectively.The results show that DCCs prepared from rice,wheat,and corn straws by sequential periodatechlorite oxidation have potential for the removal of copper ions from aqueous medium.

Simulation Analysis of Stress Field of Walnut Shell Composite Powder in Laser Additive Manufacturing Forming

A calculation model of stress field in laser additive manufacturing of walnut shell composite powder(walnut shell/Co-PES powder)was established.The DFLUX subroutine was used to implement the moveable application of a double ellipsoid heat source by considering the mechanical properties varying with temperature.The stress field was simulated by the sequential coupling method,and the experimental results were in good accordance with the simulation results.In addition,the distribution and variation of stress and strain field were obtained in the process of laser additive manufacturing of walnut shell composite powder.The displacement of laser additive manufacturing walnut shell composite parts gradually decreased with increasing preheating temperature,decreasing laser power and increasing scanning speed.During the cooling process,the displacement of laser additive manufacturing of walnut shell composite parts gradually increased with the increasing preheating temperature,decreasing scanning speed and increasing laser power.

Solid State Reaction Yielding a Mineral Utilizing Silica Obtained from an Agricultural Waste

Wollastonite, a mineral of wide industrial applications was synthesised from rice husk ash silica and limestone. A number of raw batches consisting of these starting materials, in 1:1 molar ratio, were heat treated to produce it through solid state reaction from 900℃ to 1300℃. The conducted reaction was monitored by XRD step by step. Amount of Wollastonite formed at every temperature was also studied to some extent. Analyses of the obtained data indicated that the target mineral formation was quite effective and almost proportional to a rise in temperature up to 1200℃. The results from both, XRD and chemical analysis were found in fair agreement with one another

Synthesis and optimization of high surface area mesoporous date palm fiber-based nanostructured powder activated carbon for aluminum removal

Date palm fiber(DPF)derived from agrowaste was utilized as a new precursor for the optimized synthesis of a costeffective,nanostructured,powderactivated carbon(nPAC)for aluminum(Al3+)removal from aqueous solutions using carbonization,KOH activation,response surface methodology(RSM)and central composite design(CCD).The optimum synthesis condition,activation temperature,time and impregnation ratio were found to be 650℃,1.09 hour and 1:1,respectively.Furthermore,the optimum conditions for removal were 99.5%and 9.958 mgg 1 in regard to uptake capacity.The optimum conditions of nPAC was analyzed and characterized using XRD,FTIR,FESEM,BET,TGA and Zeta potential.Moreover,the adsorption of the Al3+conditions was optimized with an integrated RSMCCD experimental design.Regression results revealed that the adsorption kinetics data was well fitted by the pseudosecond order model,whereas the adsorption isotherm data was best represented by the Freundlich isotherm model.Optimum activated carbon indicated that DPF can serve as a costeffective precursor adsorbent for Al^(3+)removal.

The Energy Consumption of Heatingin the Northeast Rural Area of China from the Perspective of the Kang and Agricultural Waste

In China, the heating energy consumption patterns of rural housing are changing due to economic development. This study investigated domestic heating in rural areas of Dalian, a city in northeast China. In rural areas of the country, heating devices such as coal boiler, radiator, and/ or air-conditioner are typically used. The Kang, as the main heating system, has been used together with other heating methods for a long time in detached houses, one-story buildings, and quadrangles. Use of the Kang in collective housing is no longer observed. In addition to coal, agricultural wastes have been used to fuel the Kang; the associated CO2 emissions with agricultural fuels are lower than from other heating equipment. Even when a combination of the Kang and other equipment is used, with agricultural waste as fuel, CO2 emissions remain relatively low.

Transformation mechanism of nutrient elements in the process of biochar preparation for returning biochar to soil

Returning biochar to soil is a heavily researched topic because biochar functions well for soil improvement. There is a significant loss of nutrients, which occurs during biochar preparation before biochar is returned to soil,thereby seriously undermining biochar's efficacy. Therefore, the transformation mechanisms of biochar p H,mass, nutrients and metals during pyrolysis under different atmospheres and temperatures were studied such that the best method for biochar preparation could be developed. Several conclusions can be reached:(1) a CO_2 atmosphere is better than a N_2 atmosphere for biochar preparation, although preparation in a CO_2 atmosphere is not a common practice for biochar producers;(2) 350 °C is the best temperature for biochar preparation because the amount of nutrient loss is notably low based on the premise of straw transferred into biochar; and(3) transforming mechanisms of pH, N, P and K are also involved in the biochar preparation process.

Chemicals,Energy,and Biomaterials from Agricultural Waste Resources in South China

Owing to its subtropical or tropical environment and climate,South China is home to unique agricultural crops such as sugar cane,pineapple,banana,cassava,and rice,which generate a large amount of lignocellulosic agricultural wastes during agricultural as well as associated industrial processing.The efficient utilization of these wastes will have a significant impact on the economy and sustainable development of South China.This paper reviews the research investigations conducted both in China and elsewhere on the conversion of wastes from these subtropical or tropical agricultural crops into useful chemicals,energy,and biomaterials.The goal of this paper is to promote and summarize the extensive investigations on these agricultural wastes for the development of biorefinery.

Isolation of Thermally Stable Cellulose Nanocrystals from Spent Coffee Grounds via Phosphoric Acid Hydrolysis

As the world's population exponentially grows,so does the need for the production of food,with cereal production growing annually from an estimated 1.0 billion to 2.5 billion tons within the last few decades.This rapid growth in food production results in an ever increasing amount of agricultural wastes,of which already occupies nearly 50%of the total landfill area.For example,is the billions of dry tons of cellulose-containing spent coffee grounds disposed in landfills annually.This paper seeks to provide a method for isolating cellulose nanocrystals(CNCs)from spent coffee grounds,in order to recycle and utilize the cellulosic waste material which would otherwise have no applications.CNCs have already been shown to have vast applications in the polymer engineering field,mainly utilized for their high strength to weight ratio for reinforcement of polymer-based nanocomposites.A successful method of purifying and hydrolyzing the spent coffee grounds in order to isolate usable CNCs was established.The CNCs were then characterized using current techniques to determine important chemical and physical properties.A few crucial properties determined were aspect ratio of 12±3,crystallinity of 74.2%,surface charge density of(48.4±6.2)mM/kg cellulose,and the ability to successfully reinforce a polymer based nanocomposite.These characteristics compare well to other literature data and common commercial sources of CNCs.

Hexavalent Chromium Adsorption from Aqueous Solution by Agricultural Waste Materials

Abilities of agricultural waste materials (walnut shell-WS, rice husk-RH, and peanut hull-PH) were tested as adsorbents for the adsorption of Cr(Ⅵ) from aqueous solution. Batch adsorption experiments were carried out to study the adsorption kinetics mechanism of Cr(Ⅵ) effect of adsorbent dosage, pH, contact time, and temperature. The best results are obtained at 15g/L adsorbent concentration, 60min contact time, 298K temperature, and 50mg/L adsorbate initial concentration at pH 2. The adsorption isotherms, using initial concentrations of Cr(Ⅵ) between 10 and 500mg/L for the Cr(Ⅵ) removal, show the maximum metal uptake capacities of adsorbent were 10.48, 6.71, and 8.54mg/g for WS, RH, and PH, respectively. And the adsorption data fitted well to the Langmuir adsorption isotherm for WS, RH, and PH with correlation coefficients of 0.9862, 0.9723, and 0.9714, respectively. Moreover, the FTIR analysis of WS, RH, and PH before and after adsorption of Cr(Ⅵ) suggested that Cr ions were combined to some functional groups of compounds contained in these materials.

Prediction and Analysis of Post-Treatment of Sustainable Walnut Shell/Co-PES Parts by Laser Sintering

In order to enhance the strength of sustainable walnut shell/Co-PES(WSPC)sintered parts,wax-filtrated posttreatment was carried out.The effects of treating fluid temperature,preheating time and immersion time on the bending strength of WSPC wax-filtrated parts were analyzed by single factor analysis method.To obtain an accurate model for predicting the bending strength of the WSPC wax-filtrated part,the experiments were involved by using Box-Behnken design(BBD).Main parameters,such as treating fluid temperature,preheating time and immersion time,and their interactive effects were analyzed through analysis of variance(ANOVA)and graphical contours.The results demonstrated that all parameters’direct effects were significant to bending strength of the WSPC wax-filtrated part.Its optimum value was 5.0 MPa when the treating fluid temperature of 70°C,preheating time of 50 min,and immersion time of 20 s.The predicted models effectively validated had good predicting accuracy.The WSPC wax-filtrated part using optimal processing parameters was processed by investment casting,and then the metal casting of dimensional stability and smooth surface was obtained.Investment casting was done using WSPC wax-filtrated parts under optimal process parameters and then metal parts with stable structure size and smooth surface can be obtained,which indicates that WSPC material can be used for investment casting.

Strength,porosity,and chloride resistance of mortar using the combination of two kinds of pozzolanic materials

This article presents a study on the resistance to chloride penetration, corrosion, porosity, and strength of mortar containing fine fly ash （FA）, ground rice husk-bark ash （RB）, and ground bagasse ash （BA）. Ordinary Portland cement （CT） was blended with a single pozzolan and two pozzolans. Strength, porosity, rapid chloride penetration, immersion, and corrosion tests were performed to characterize the mortar. Test results showed that the use of ternary blends of CT, FA, and RB or BA decreased the porosity of the mortar, as compared with binary blended mortar containing CT and RB or BA. The resistance to chloride penetration of the mortar improved substantially with partial replacement of CT with FA, RB, and BA. The use of ternary blends of CT, FA and RB or BA produced the mortar with good strength and resistance to chloride penetration. The resistance to chloride penetration was higher with an increase in the replacement level due to the reduced calcium hydroxide.

STUDIES ON TUNG OIL COATED REGENERATED CELLULOSE FILMS WITH WATERRESISTANCE

Regenerated cellulose films with water-resistance were obtained by an improved method ofpreparing cellulose cuoxam solution from pulps of agricultural wastes (linters, wheat straw, reedand Bamao). Experimental results showed that the mechanical properties of both the dry. and wetfilms were excellent. Data from IR, SEM and tensile strength measurements implied that thesignificant improvement of water-resistance of the films was due to the cohesion between the thinTung oil covers with hydrophobicity and the regenerated cellulose films. The films werecompletely biodegraded after being buried in soil for 100 days. The transmittance of the filmsderived from linter and reed in visible band range were 80-90%.

Recent Advance on Torrefaction Valorization and Application of Biochar from Agricultural Waste for Soil Remediation

With the increase of global proportion of soil pollution and the number of areas at risk,researchers have sought to develop various pathways to repair or relieve the pollutants in soil.Among them,biochar represents one multi-dimensional soil amendment which has got great deal of attention on its physicochemical properties towards the removal or mitigation of contaminants in soil.A variety of agricultural wastes like straw and manure prepared from different torrefaction process have been employed as feedstock for the production of biochar,which can be applied to the contaminated soil to facilitate the growing environment for crops,and to improve soil fertility and microbial environment.In addition,the utilization of biochar for soil remediation is also considered as a pro-cess of carbon sequestration.The purpose of this review is to summarize the latest research progress in torrefac-tion processes and mechanism of agricultural waste,the effects of different torrefaction methods on the formation and properties of biochar were explained,coupled with the effects of process parameters.Especially,the conver-sion and mechanisms of biochar prepared from agricultural wastes composed mainly with lignocellulosic material were discussed,and the characteristics of biochar prepared for improving soil physical and chemical character-istics,microbial community characteristics,nutrients,and the stability and relief of soil pollutants,especially heavy metals,are compared.Finally,this work discussed the application and future technical challenges of soil remediation based on agricultural waste derived biochar.

Review of Microbial Inoculation Agent Used in Composting

Microbial inoculation agent has been widely used in waste disposal and waste recycling. In this paper, the principle of fermentation in the composting of agricultural waste and the impact of microbial inoculation agent on composting were reviewed.The research and the application of microbial inoculation agent were also introduced. Based on the trend of the research, the promising prospect of microbial inoculation agent was discussed.

Current Situation and Suggestions for Energy Utilization of Agricultural Waste in Hubei Province

Energy utilization is high-value use pattern of agricultural waste, and is main development direction of agricultural biomass energy industry in China. Planting and breeding industry in Hubei Province occupies important position in whole country. Agricultural waste resources are rich, and it has huge potential for developing agriculturel biomass energy. By statistical data during 2000 -2011, we analyzed current situation and problem for energy utilization of agricultural waste in Hubei Province, and put forward several countermeasures and suggestions, vigorously promoting energy utilization of agricultural waste.

Characterization of Peanut Shells for Their Valorization in Earth Brick

Peanut shells from Burkina Faso were characterized using mineralogical, microstructural and chemical methods to perform its possibility to be used as reinforce in adobe bricks. It consists of cellulose (48 wt%), hemicellulose (3 wt%) and lignin (28 wt%). The peanut shells were characterized by high porosity and showed water absorption around 198% at 72 hours. Its chemical composition is essentially composed of silica, iron oxides, alumina and calcium oxide. Its microstructure showed that the peanut shells were a compilation of microfibers with high porous of borders. In watery solution, the peanut shells released polyphenols. Thermal conductivity of peanut at 25 °C was 0.155 ± 0.021 W/mK. The physico-chemical characteristics of peanut shells were similar to those found with agricultural by-products used in adobe reinforce.

Valorization of Agricultural Waste: Theoretical Estimation and Experimental Biomethane Yield from Cashew Nut Hulls

Biomethane potential production from cashew nut hulls, an agricultural waste, was carried out using old and fresh hulls as substrates. Samples were taken from old hulls (around 8 years old) and fresh hulls produced in cashew scale transformation units at Bobo Dioulasso/Burkina Faso. Physicochemical parameters showed that cashew hulls can be a good candidate for anaerobic digestion. But high acidity, total phenols and lignin tenor could be a constraint for anaerobic bacteria. Theoretical biochemical methane potential showed high value of 666.937 CH4 L. (Kg VS)-1 and 526.206 CH4 L. (Kg VS)-1 for crushed fresh and powdered old hulls, respectively. Experimental biochemical methane potential showed significantly low potential of 1.982 CH4 L. (Kg VM)-1 and 46.840 CH4 L. (Kg VM)-1 for fresh and hold hulls, respectively. Pretreatment for optimization, chemical composition and co-digestion system must be expected for a better anaerobic digestion performance.

Effect of Partial Replacement of Ordinary Portland Cement (OPC) with Ghanaian Rice Husk Ash (RHA) on the Compressive Strength of Concrete

The cost of cement has made concrete production expensive such that the housing deficit in developing countries is on the rise despite all the efforts by governments and other stakeholders to produce affordable housing units for the populace. Ashes of agricultural products such as rice husk, known as mineral admixtures may have pozzolanic characteristics which would be more beneficial to the housing industry in terms of strength gain and economy than being pollutants to the environment. Rice Husk Ash (RHA), because of its finely divided form and very high silica content and amorphousness, proved to be useful for strength gain of Rice Husk Ash Concrete (RHAC). Rice husk ash was manufactured by uncontrolled burning, ground, sieved and replaced with cement at 0%, 5%, 10%, 15%, 20% and 25% in mass for the mixes C20, C25, C30 and C35 where their compressive strengths were verified at 3, 7, 14, 21, 28, 56, 90 and 180 days. The X-ray diffraction pattern list indicated amorphous as well as diffused peak of about 8000 counts of SiO2 representing crystalline structures identified as cristobalite. A physical examination of the RHA showed very fine appearance, grey color and specific gravity of 2.06. The chemical analysis also revealed the existence of oxide content to be 55.8% representing 0.78% of Fe2O3, 54% of SiO2 and 1.06% of Al2O3 representing 20.23% lower than the minimum value of 70% required for pozzolans. Generally, the compressive strength values decreased as the RHA content in the mixes increased but when compared to the control concrete the optimum replacement percentage of Ordinary Portland Cement (OPC) with RHA at 5% showed an increase above the control concrete for C20 mix. The increase in the RHA in the mixes resulted in the high demand for water in all the mixes.

Experimental Investigation on the Thermal Properties of Gypsum Plaster-Rice Husk Ash Composite

This experimental investigation aims at evaluating the thermal properties of rice husk ash (RHA)—filled gypsum plaster composite for potential applications, as insulating materials. The thermal conductivities of composites of gypsum plaster reinforced with RHA at 0%, 10%, 20%, 30%, and 40% volume fractions were determined experimentally using Lee’s disc method. The experimental results show that integrating RHA reduces the thermal conductivity of gypsum plaster and improves its insulation capacity. The results obtained from the experiments were compared with the Rule of Mixture Model, Maxwell Model, and Russell Model. It was observed that the thermal conductivities obtained from experiments and the theoretical models decreased with an increase in the volume fraction of RHA. The errors associated with the models with respect to experimental results are on the average of 28.7% for Mixture Rule, 31.6% for Russel Model, and 18.8% for the Maxwell Model. An agricultural waste like RHA can be beneficially used for the preparation of composites and, due to improved insulation capability, these composites can be used for applications such as insulation boards and sheathing, hardboard, ceilings of roofs, decorations, etc.