Alkaline Residue Research Articles

Ecotoxicity of alkaline residue from the pulp and paper industry to soil faunal organisms

The increased production and expanding demand for cellulosic products have required companies to provide solutions for the proper disposal of generated residues without compromising soil quality. In this context, the current research aimed at evaluating the ecotoxicological impacts of dregs application in subtropical soils. The experiments were carried out with the earthworm Eisenia andrei, the springtail Folsomia candida, and the potworm Enchytraeus crypticus in two subtropical soils (Neosol and Cambisol) collected in the southern region of Brazil. The considerable differences in texture and organic matter content motivated the choosing of these soils. The reproductive rate of all organisms was influenced, with varying EC50 values depending on the soil type. However, more pronounced effects were observed for Neosol. The springtail F. candida proved to be the most sensitive to contamination (EC50 = 5.8 g kg−1 for Neosol and 48.5 g kg−1 for Cambisol), followed by the earthworm E. andrei (EC50 = 62.4 g kg−1 for Neosol and 129.5 g kg−1 for Cambisol) and the potworm E. crypticus (EC50 = 67.2 g kg−1 for Neosol and 230.4 g kg−1 for Cambisol). As a result, while dregs can be used to correct soil acidity, they have been shown to have negative effects on important organisms responsible for functions critical to maintaining ecosystem quality.

Efficient biodiesel production by sulfonated carbon catalyst derived from waste glycerine pitch via single-step carbonisation and sulfonation

Glycerine pitch is a highly alkaline residue from the oleochemical industry that contains glycerol and contaminants, such as water, soap, salt and ash. In this study, acidic heterogeneous glycerol-based carbon catalysts were synthesised for biodiesel production via single-step partial carbonisation and sulfonation using pure glycerol and glycerine pitch, producing products labelled as SGC and SGPC, respectively. Carbon materials were obtained by heating glycerol and concentrated sulfuric acid (1:3) at 200℃ for 1 h. The produced SGC and SGPC displayed high densities of sulfonic group (–SO3H), i.e. 1.49 and 1.00 mmol·g−1, respectively, alongside carboxylic (–COOH) and phenolic (–OH) acid. In the catalytic evaluation, excellent oleic acid conversions of 96.0 ± 0.4 % and 92.4 ± 0.5 % were achieved using SGC and SGPC, respectively, under optimised reaction conditions: 1:10 M ratio of oleic acid to methanol, 5 % (w/w) catalyst, 64℃ and 5 h. SGPC was found to be recyclable with 68.5 % conversion after the 6th cycle, which was attributed to the loss of –SO3H and catalyst deactivation by the deposition of oleic acid on its surface. Remarkably, despite the impurities present in the glycerine pitch, the obtained results demonstrated that the reactivity of SGPC is comparable to SGC and superior to that of commercial solid acid catalysts, which demonstrated that the presence of impurities appears to have minimal impact on the production of carbon materials and their properties.

Neutralização de Drenagem Ácida de Rochas com Lama Vermelha de Bauxita: Ensaios de Batelada em Laboratório

Acid Rock Drainage (ARD) is one of the world's most challenging environmental issues. Alkaline amendments to barriers for ARD prevention or direct ARD alkaline treatment have been routinely used for ARD management. In turn, bauxite red mud (BRM) is an alkaline residue from the alumina industry, with annual average production close to 120 million tons. So the use of BRM for ARD neutralization seems to be a good alternative and must be investigated. The main objective of this experiment is to assess suitable proportions of BRM to treat ARD under the perspective of waste management procedures. So, laboratory short-term batch equilibrium tests were carried out using different volumetric and mass proportions. The use of a volumetric approach was intended to simulate the mixture of BRM pulp with the ARD liquid solutions, while the mass approach refer to the mixtures of dewatered BRM and ARD. The pH and metal removal percentage, called here as extraction, were respectively used as neutralization and treatment efficiency parameters. The results have showed that BRM was efficient for ARD neutralization on BRM volumetric proportions greater than 60% and solid (BRM):liquid(ARD) ratio of 1:1.5. This ratio result on extraction values greater than 90% for most of the ARD chemicals.

Dual-value utilization of calcium-silica slag: Sequestration of CO2 to recover high-purity vaterite with silica fertilizer as a by-product

Calcium-silica slag (CSS) is a highly alkaline residue, rich in calcium, generated during the chemical pre-desilication process of medium- and low-grade bauxite. Mismanagement of CSS can result in detrimental environmental impacts. This study developed a novel method that combines CO2 sequestration with CSS utilization, thereby achieving simultaneous dual-value enhancement of CSS and eliminating waste discharge. Under optimized Ca2+ leaching and carbonation conditions, a remarkable Ca2+ extraction efficiency of 96.93 % was attained, while the carbonation efficiency reached 99.37 %. Consequently, this process sequestered 301.7 kg of CO2 per ton of CSS. The leaching process of Ca2+ in NH4Ac solution was realized based on the unreacted shrinking core model, which accounts for internal diffusion and chemical reaction as factors influencing leaching. The resulting carbonated product exhibited outstanding characteristics: high-purity vaterite composed of 97.43 wt% CaCO3 with a whiteness level of 95.2 %. By regulating the carbonation temperature, the crystal particulate size distribution of CaCO3 was tailored to meet specific requirements for various applications. Furthermore, silicon content was enriched in the leaching residue, increasing the effective SiO2 content from 25.2 wt% to 53.12 wt% and reducing the pH from 12.23 to 7.34, rendering it a suitable silica fertilizer for agricultural production.

Rinse model implementation of alkaline detergent in clean‐in‐place process with gradual flow reduction for economy of water and effluent reduction

AbstractDemand for water savings in clean‐in‐place (CIP) process has increased due to the limited offer of this natural resource. Thus, this work investigated the CIP with variable flow in the rinse step in a stainless steel piping system contaminated with alkaline detergent residues compared to CIP with constant flow for rinse water (RW) saving purposes. In addition, the dynamics of the conductivity of the effluent of the CIP system, typically found in dairies, was investigated and water consumption estimated. For this purpose, a CIP prototype was used, which was subjected to cleaning with alkaline detergent (NaOH) at 70°C for 15 min and later rinsed, evaluating the flow reduction effect. The removal of alkaline residue was evaluated under steady state and variable conditions using computer simulation in software Matlab™/Simulink™. The dynamics of alkaline residue removal was modeled using the first order transfer function with dead time (FOPDT) and the gradual flow reduction strategy for rinsing was predicted using the interpolation of the models. The results showed that both strategies were significant for the residues of detergent removal. However, the reduction in spent RW volume was more significant for the variable flow, representing 35% of potable water savings compared to the conventional process with constant flow, what suggests an interesting strategy to reduce the environmental impact caused by the CIP process. Finally, the FOPDT models were effective in predicting the rinse dynamics and determining the time of the process.Practical applicationsStrategies to reduce rinse water consumption and to guarantee food safety are essential. Variable rinse flow can be used in dairy industries to improve economy of water and energy during rinse stage of a CIP process in comparison with the time spent considering the stationary flow process, commonly employed in dairy. In addition, this change is attractive, as it can be made with only adjustments to the control system, not necessarily requiring new equipment.

Behaviour of high-density concrete and low-density concrete in alkaline environment

Every year, various industries throughout the world create more than two billion metric tons of alkaline residue. The effectiveness and strength of concrete are significantly impacted by these leftovers. It's critical to comprehend how alkaline residues behave in concrete in order to minimize or lessen the issues they create. The purpose of the current research is to compare the strength characteristics of high- and low-density concrete in an alkaline environment. Various low-density aggregates, including pumice and vermiculite, are used to create low-density concrete mixtures. To create low-density concrete, one mixture substitutes pumice material for all of the typical coarse aggregate, while another substitutes vermiculite for 30% of the fine aggregate. Utilizing various high-density aggregates, such as barite and haematite, allows for the creation of high-density concrete mixtures. Barite and haematite are used as coarse aggregate in two distinct mixes to create high-density concrete by completely replacing the conventional coarse aggregate in each mix. Concrete examples are subjected to two distinct curing processes after casting. In one curing condition, concrete specimens are cured using regular water; in the other, they are cured using alkaline water after being cured in normal water for seven days. Using NaOH pellets, an alkaline solution with a pH of 13 is produced. Rapid Chloride Penetration, Split-Tensile Strength, Flexural Strength, and Compressive Strength To determine the impact of alkaline curing on concrete specimens, test results from specimens that were cured in an alkaline environment were compared to those of standard specimens.

Kinetics of H2S removal using alkaline residue as in-bed sorbent in fluidized bed gasification of biomass and wastes

The use of alkaline residue from the acetylene industry (carbide slag, CS) as in-bed sorbent to remove H2S from syngas from biomass/waste fluidized bed (FB) gasification was investigated. Measurements were conducted in a laboratory FB applying differential conversion technique, tracking the reaction using both gas measurements and solid analysis. Apparent reaction kinetics was obtained, without external mass transfer limitations, for different gas mixtures containing CO2, H2O, CO, H2 and CH4, having relatively low H2S concentration (500–1000 ppm). The addition of CO2 and H2O to an N2-H2-H2S mixture showed that the reaction rate was reduced in the presence of these species. Varying the H2 concentration between 7 and 14% in simple (N2-H2-H2S) reactive gas mixtures did not affect the results, while both CO and H2 potentially affected the reaction rate if also CO2 was present in the gas. Other operating parameters, such as sorbent particle size, sulfidation- and calcination temperature also affected the CaO sulfidation rate, which increased with temperature between 800 and 900 °C and was enhanced by higher calcination temperature. Specific surface area and pore size distribution of the calcined CS was measured before and after the sulfidation reaction, showing that CS maintained a large fraction of its original pore volume even after most of the CaO had been converted into CaS. The sulfidation rate of calcined limestone was also measured for comparison showing that the reaction rate using CS was slightly lower, but similar to that using limestone, showing that CS is a promising alternative to conventional calcium-based sorbents for high temperature H2S removal, contributing to promote the circular economy, while avoiding the current stacking of CS at the acetylene production sites.

A New Promising Plant Defense Stimulator Derived from a By-Product of Agar Extraction from Gelidium sesquipedale

Stimulation of plant defenses by elicitors is an alternative strategy to reduce pesticide use. In this study, we examined the elicitor properties of a by-product of the industrial extraction of agar from the red alga Gelidium sesquipedale. Agar extraction process leads to the formation of an alkaline residue which is poorly valorized. This by-product has been analyzed for its chemical composition. It contains 44% minerals and, among the organic compounds, sugars are the most represented and encompass 12.5% of the dry matter. When sprayed on tomato plants, this by-product enhanced the levels of defense markers such as peroxidase or phenylalanine ammonia lyase activities. Furthermore, this treatment increased the expression levels of the pathogenesis-related gene, PR9 encoding peroxidase. A field trial conducted on grapevine revealed that spraying treatment with this by-product resulted in a reduction of the macroscopic disease symptoms induced by Plasmospora viticola, with 40 to 60% efficacy. These results indicate that this agar extraction by-product could be used as a plant defense stimulator.

Analyzing the phenolic enriched fractions from Nixtamalization wastewater (Nejayote) fractionated in a three-step membrane process

Nejayote is recognized as the main by-product resulting from the nixtamalization process of maize kernels, which is categorized as an alkaline residue with a chemical composition based on carbohydrates (37.8–55.7%), fiber (22.8–25.5%), protein (4.9–7.4%), and lipids (0.4–1.5%). In addition, Nejayote has an extensive content of simple (e.g., phenolic acids) and complex phenolic compounds (e.g., anthocyanins), which are responsible for the pigmentation and antioxidant activity of maize; therefore, there is a need of their identification depending on the type of maize. The current research has focused on the efficient extraction and identification of the phenolic acids contained in Nejayote after the processing of different types of maize. The target of this work was to fractionate Nejayote from white (NWM), red (NRM), and purple maize (NPM), using three different membranes, such as microfiltration (MF with a pore size of 1 μm) and ultrafiltration (UF100 and UF1 with a molecular weight cut-off of 100 kDa and 1 kDa, respectively), which were strategically applied to extract phenolic acids while retaining other molecules. Such a membrane system exhibited a retention in the first stage of almost all carbohydrates (MF-Retentate: ca. 12–19 g GE/L), while second stage (UF100-Permeate) a concentration of phenolic components was recovered ranging from 768 to 800 mg GAE/L. Finally, in the third stage (UF1-Permeate), 14 phenolic acids were identified, including ferulic and p-coumaric acids, derived from caffeic and ferulic acids, along with other molecules (e.g., glucose and fructose).

Influence of Brewer's Spent Grain Compounds on Glucose Metabolism Enzymes.

With a yearly production of about 39 million tons, brewer’s spent grain (BSG) is the most abundant brewing industry byproduct. Because it is rich in fiber and protein, it is commonly used as cattle feed but could also be used within the human diet. Additionally, it contains many bioactive substances such as hydroxycinnamic acids that are known to be antioxidants and potent inhibitors of enzymes of glucose metabolism. Therefore, our study aim was to prepare different extracts—A1-A7 (solid-liquid extraction with 60% acetone); HE1-HE6 (alkaline hydrolysis followed by ethyl acetate extraction) and HA1-HA3 (60% acetone extraction of alkaline residue)—from various BSGs which were characterized for their total phenolic (TPC) and total flavonoid (TFC) contents, before conducting in vitro studies on their effects on the glucose metabolism enzymes α-amylase, α-glucosidase, dipeptidyl peptidase IV (DPP IV), and glycogen phosphorylase α (GPα). Depending on the extraction procedures, TPCs ranged from 20–350 µg gallic acid equivalents/mg extract and TFCs were as high as 94 µg catechin equivalents/mg extract. Strong inhibition of glucose metabolism enzymes was also observed: the IC50 values for α-glucosidase inhibition ranged from 67.4 ± 8.1 µg/mL to 268.1 ± 29.4 µg/mL, for DPP IV inhibition they ranged from 290.6 ± 97.4 to 778.4 ± 95.5 µg/mL and for GPα enzyme inhibition from 12.6 ± 1.1 to 261 ± 6 µg/mL. However, the extracts did not strongly inhibit α-amylase. In general, the A extracts from solid-liquid extraction with 60% acetone showed stronger inhibitory potential towards a-glucosidase and GPα than other extracts whereby no correlation with TPC or TFC were observed. Additionally, DPP IV was mainly inhibited by HE extracts but the effect was not of biological relevance. Our results show that BSG is a potent source of α-glucosidase and GPα inhibitors, but further research is needed to identify these bioactive compounds within BSG extracts focusing on extracts from solid-liquid extraction with 60% acetone.

Effect of Carbonation on the Leachability of Solidified/Stabilized Lead‐Contaminated Expansive Soil

Lime, fly ash, and alkaline residue are used widely as effective binders to solidify/stabilize heavy metal‐contaminated expansive soil. Carbonation, however, may influence the effectiveness of solidification/stabilization (S/S) by decomposing hydration products and decreasing pH, which would seriously damage the long‐term durability of stabilized soils. This study focused on the variation of leaching characteristics of solidified/stabilized lead‐contaminated expansive soils before and after accelerated carbonation under the leachant of pH 3 and 5 by the semidynamic leaching test. After semidynamic leaching, leaching indexes such as the effective diffusion coefficient (De), leachability index (Lx), and slope (rc) were used to reveal the ion leaching mechanism. The results indicated that the amount of Pb2+ and Ca2+ leached out under different pH conditions increased after carbonation, which confirmed that carbonate on solidified/stabilized lead (Pb) had a negative impact. Additionally, the De values of Pb2+ and Ca2+ varied in the range of 1.16E − 10 cm2/s to 1.71E − 07 cm2/s, which demonstrated that ion migration was low. The contaminated soil solidified by lime and AR could be used in “controlled utilization” as Lx was higher than 9, and the leaching process was controlled by a dissolution reaction according to the analysis of rc. Moreover, the strong acidic leachant (pH = 3) resulted in more ions leaching out and lower pH in leachate compared with a mildly acidic leachant. Finally, with literature and experimental results, we found that the main reason for the increase of lead ion filtration of the carbonation reduced the pH value of the matrix and made the hydration products denatured and decomposed.

Constructed wetlands for the treatment of bauxite residue leachate: Long term field evidence and implications for management

Alkaline leachate from bauxite residue disposal areas is likely to require treatment for post-closure. Traditional treatment methods are not attractive in the long-term due to management requirement, energy input and operational logistics and passive approaches offer an alternative approach. Constructed wetlands are widely cited as a potential treatment option but there is limited data on long term field-scale applications.Treatment of alkaline residue leachate was assessed over a 52 month period and showed effective pH reductions from ca. pH 11.2 (inflow) to 7.2 (outflow). Trace element content measured during the 4th year of operation demonstrated effective reduction in trace element (Al 17,256 μg/l to 330 μg/l; V 140 μg/l to 13 μg/l) with no evidence of toxicity in test species Vibrio fischeri, Skeletonema costatum, Tisbe battagliai and Oncorhynchus mykiss in the wetland outflow. Sediment analysis found some increases in trace element content but no evidence of accumulation in Phragmites was found in vegetation sampling.Longevity and management requirements for constructed wetland treating alkaline bauxite residue leachate are more likely to be impacted from increases in soil Na and pH. Increases are more evident in front sections of wetland but it is proposed that loading to wetlands can be decreased by incorporation of other passive technologies within the overall treatment approach and by feeding different sections of the wetlands on a cyclical basis.

Application of KOH modified seaweed hydrochar as a biosorbent of Vanadium from aqueous solution: Characterisations, mechanisms and regeneration capacity

Abstract Vanadium exists as a mobile and toxic trace metal in many alkaline residue leachates. Its removal and recovery not only reduces a global environmental risk but is also critical to the emergence of innovative technologies and the circular economy. In parallel, the use of treated biomass feedstock is receiving increased attention as a low cost adsorbent for toxic metals in wastewater. This study investigated the adsorption of Vanadium (V) from aqueous solution by KOH modified seaweed (Ascophyllum nodosum) hydrochar (HCKOH). The results showed that HCKOH is an effective V(V) adsorbent, achieving maximum uptake of 12.3 mg g−1 at solution pH 4, 60 min contact time and temperature 293 K. The kinetics followed a pseudo second order model with film diffusion controlling the overall adsorption rate. The type I adsorption isotherm was well fitted to a Langmuir model (qm = 12.3 mg g-1, R2 = 0.970, RMSE = 0.66) and a thermodynamic study indicated that the V(V) adsorption was both exothermic and spontaneous. The low enthalpy change (-10.97 kJ mol−1) indicated a weak binding of V(V) to HCKOH pointing to the possibility of V recovery. The impact of co-existing cations on V(V) uptake was negligible for Na(I) and Ga (III) but was reduced slightly for Al(III). Desorption and re-adsorption results (3 cycles) indicated that HCKOH has reusable potential to remove and recover V(V) from waste leachates.

Floatable magnetic aerogel based on alkaline residue used for the convenient removal of heavy metals from wastewater

The present work introduces a novel strategy for preparation of a recyclable aerogel absorbent for heavy metal purification of industrial wastewater. The absorbent (Fe3O4/SA-AR) is based on a combination Fe3O4, alginate (SA) and industrial alkaline residue (AR) waste, forming a cost-efficient and easily recyclable spherical aerogel. The magnetic aerogel spheres of the Fe3O4/SA-AR are light-weight with a loose porous structure and a mechanical strength 10 times that of conventional SA aerogels, thus sustaining up to 20 cycles of compression-relaxation. This excellent structure stability guarantees long-term integrity and floatability of the aerogel spheres in water. Adsorption experiments on the heavy metal Cd(II) suggested that equilibrium was approached within 2 h. The maximum adsorption capacity was 38.83 mg/g, higher than reported for conventional SA aerogel absorbents. After 5 cycles of adsorption–desorption, the aerogel spheres still maintained an adsorption efficiency of 90%, and had good stability and reusability. Studies on kinetic and adsorption isotherm models showed that the adsorption of Cd(II) to Fe3O4/SA-AR correlated well with the pseudo-second-order kinetic model and the Langmuir isotherm model. FTIR, SEM-EDS and XPS analyses indicated that the adsorption of Cd(II) to the Fe3O4/SA-AR aerogel was mainly driven by formation of OH complexation, electrostatic adsorption and ion exchange. In summary, this work suggests a new route for synergetic resource utilization of value-less and pollutive alkaline residual for the removal of heavy metals in wastewater.

Simultaneous Enhancement of Volatile Fatty Acids Production and Dewaterability of Waste-Activated Sludge Using Calcined Alkaline Residue

Abstract This study reported a novel and resource-economical strategy for enhancing volatile fatty acids (VFAs) production and sludge dewaterability from sludge anaerobic digestion via codigesting ...

Research on pavement performance of mixed filler with alkaline residue-expansive soil

The expansive soil, a special clay, can cause crack, bulge, landslides and other accidents in the highway subgrade. To reduce the harm of expansive soil and realize the resource utilization of alkaline residue which is industrial solid waste, different ratio of alkaline residue and expansive soil with medium expansive potential are mixed as subgrade filling. A series of experiments are carried out for the pavement performance of the mixture. The results show that the swelling ratio of the mixture decreases significantly with the mixing rate. The longer the curing time is, the lower the swelling ratio will be. And the expansibility is completely eliminated in 28 days. The unconfined compressive strength(UCS) heightens with the growth of mixing rate, and when the mixing rate reaches 30%, the increasing level gradually stabilizes. Similarly, the curing time has an obvious effect on the unconfined compressive strength. After cured for 14 days, the UCS of samples is twice of that not cured. And the cohesion goes up in first stage, then decreases, and peaked as the mixing rate reaches to 30%. However, the internal friction angle changes little. The CBR increases with the increase of mixture ratio and the curing time. In addition, the mechanism of alkali residue modifying curing expansive soil is mainly based on the substitution effect of alkali residue, coagulation reaction and ion exchange of alkali residue - expansive soil.

Investigations on Engineering Properties of Solidified/Stabilized Pb‐Contaminated Soil Based on Alkaline Residue

Solidification/stabilization (S/S) has been considered as one of the most effective techniques for remediation of the heavy metal‐contaminated sites. Among various binders adopted in S/S, alkaline residue (AR) could be considered as a new binder to treat heavy metal‐contaminated soil due to its strong adsorptive capacity for heavy metal ions. So in this paper, the strength, leaching, and microstructure characteristics of the solidified/stabilized Pb‐contaminated soil by using alkaline residue are systematically investigated. Test results present that the unconfined compressive strength (UCS) of the treated soil will increase, while the leached Pb2+ concentration will decrease, with the increase of the alkaline residue content in the specimen. The UCS increases significantly with the curing time increasing during the initial 28 days, after which the UCS of the specimen becomes stable. The leached Pb2+ concentration decreases significantly at the initial 28 days followed by a stable trend with curing time increasing. The UCS decreases and the leached Pb2+ concentration increases with the increase of the initial Pb2+ concentration in the specimen. The microstructural analysis performed by scanning electron microscope (SEM) showed that the increase of the alkaline residue content and curing time will result in more hydration products and densified microstructure, which could effectively improve the engineering properties of the specimen.

Local properties of filter cakes formed from pH-adjusted bauxite residue slurries

Abstract Solid-liquid separation of bauxite residue is a topical issue in the alumina industry, not least due to the great quantity and problematic properties of this highly alkaline residue. The objective of this contribution is to provide deeper knowledge about the solid–liquid separation of pH-adjusted (pH 11) bauxite residue by investigating the local filtration properties of filter cakes produced with a piston press. Two bauxite residue samples having different particle size distribution were investigated. Measured local data of the hydrostatic pressure and solidosity was used together with flow rate data to calculate local specific filtration resistance as well as compressibility data. For the investigated pressure range (0.2–2 MPa) it was found that the residue formed slightly/moderately compressible filter cakes with a specific cake resistance between 5·1011 to 1.5·1012 m/kg. The sodium recovery and final cake solidosity were strongly dependent on the applied pressure, but only to a minor extent on the particle size reduction obtained by the applied mechanical treatment. The filter cakes formed from the mechanically treated samples did, however, display a somewhat higher pressure dependence for the local specific filtration resistance compared to the non-ground samples.

Corrective Potential of Alkaline Residue (Dregs) from Cellulose Industry in an Acid Soil Cultivated Under No-tillage

ABSTRACTThe use of alkaline residues from cellulose industry can increase soil fertility and crop productivity, but some of these residues, such as dregs, can also reduce soil physical quality. This study aimed to evaluate the effects of the dregs compared to lime as corrective for soil acidity applied on the surface under no-tillage. The treatments applied, half in 2004 and half in 2006, were: without corrective; dregs rates of 3.25, 6.5 and 13 Mg ha−1 and dolomitic lime rates of 5.25 and 10.5 Mg ha−1. After 5.5 years since the first application, soil chemical and physical attributes were determined, as well as soybean yield in 2010 and bean yield in 2011. Positive effects were observed on the soil chemical attributes with the application of dregs or lime, such as increased pH, calcium content, cation exchange capacity, and base saturation, and decreased the aluminum saturation. However, it was observed increase in sodium content and calcium/magnesium ratio with the application of dregs, however without impairing the soil physical quality. The soybean and bean yield increased in a similar way using dregs or lime. These results indicate the possibility of using dregs as corrective of soil acidity.

Study on Application of Alkaline Residue Stabilized Soil in Pavement Subbase

To analyze physical properties and chemical composition of alkaline residue from Weifang and detect on the feasibility used in subbase of secondary and under secondary level road. Alkaline residue is firstly added to varieties of materials such as clay, lime, fly ash etc, forming alkaline residue stabilized soil. Then, alkaline residue stabilized soil of the different ratio is proceeded on indoor compaction test, unconfined compression test, triaxial shear test. Different ratio tests show that alkaline residue soil added to lime or lime-fly ash should perfectly improve unconfined compressive strength and shear strength and meet the specification requirements. Alkaline residue applying to the road pavement base is feasible.