Performance evaluation of laterite soil embankment stabilized with bottom ash,coir fiber,and lime

In tropical regions,heavy rainfall induces erosion and shallow landslides on road embankments.Cement-based stabilization methods,common in these regions,contribute to climate change due to their high carbon footprint.This study explored the potential application of coir fiber-reinforced laterite soil-bottom ash mixtures as embankment materials in the tropics.The objective is to enhance engineered embankment slopes'erosion resistance and stability while offering reuse options for industrial byproducts.This study examined various mix designs for unconfined compressive strength(UCS)and permeability,utilizing 30%bottom ash(BA)and 1%coir fiber(CF)with varying sizes ranging from 10 to 40 mm,6%lime,and laterite soil(LS),followed by microstructural analyses.The results demonstrate that the compressive strength increases as the CF length increases to 25 mm.In contrast,permeability increases continuously with increasing CF length.Lime-treated mixtures exhibit superior short-and long-term strength and reduce permeability owing to the formation of cementitious materials,as confirmed by microstructural analyses.A lab-scale slope box was constructed to evaluate the surface erosion of the stabilized laterite soil embankment.Based on the rainfall simulation results,the LS-BA-CF mixtures show better resistance to erosion and deformation compared to untreated LS,especially when lime is added to the top layer.This study provides insights into a sustainable and cost-effective approach for slope stabilization using BA and CF,offering a promising solution for tropical regions susceptible to surface erosion and landslides.

Influence of the Granular Class of Crushed Granites on the Litho-Stabilization of Samo Laterites (South-East of Côte d’Ivoire)

Most of the laterites found in Ivory Coast do not meet the technical conditions to be used in their natural state for the design of road foundations. Also, to meet the growing needs for road materials, various amendments are made to them, including litho-stabilization. Thus, this study proposes to understand the influence of the granular class of natural aggregates on the performance of laterites. To achieve this objective, different proportions of crushed granites of class 0/5, 0/15 and 5/15 have been incorporated into the soils of southern Côte d’Ivoire, especially in Samo. This modified soil has been subjected to mechanical tests such as the modified Proctor and CBR test. The results obtained show that the dry densities of the incorporated laterites containing crushed granites increase with the content of natural aggregates and decrease with the increase in the water content. Likewise, the CBR bearing indices at 95% of the Modified Optimum Proctor of the different compositions (laterites + crushed granites) increase with the proportion of aggregates. The addition of coarse aggregates to the laterites therefore promotes the establishment of a framework which improves its bearing capacity. From 20% to 30% crushed granites respectively of class 0/15;0/5 and 5/15, the values of the CBR obtained are greater than those of 30% therefore these modified soils can be used as a foundation layer for traffic of T1, T2 and T3 type. Likewise, the laterites’ mixtures with at least 40% crushed granites of class 0/15 and 0/5 can also be used for the foundation and base layers.

Relative Dielectric Permittivity Variations during Compaction as a Mean of Compaction Quality Control: Case Study on Laterite Samples from Senegal

This study explores an alternative to the classical use of direct methods, as water content and dry density measurements, for compaction quality control. For this purpose, the dielectric properties of lateritic materials are determined by radar method and are compared with the permittivity determined from the Topp formula and from the CRIM model. This approach allowed to establish a relationship between the geotechnical properties determined during compaction such as dry density, water content or porosity with dielectric permittivity. The obtained results made it possible to determine an optimum dielectric permittivity corresponding to the optimum dry density and the optimum water content that could be used for non-destructive in situ compaction testing. Such an approach should improve the implementation and effectiveness of in situ compaction quality control of geotechnical infrastructures.

Effect of Polyethylene Terephthalate Plastic Waste on the Physico-Mechanical and Thermal Characteristics of Stabilized Laterite Bricks

The present work investigated the effect of polyethylene terephthalate (PET) plastic waste on the physico-mechanical and thermal properties of cement-stabilized laterite bricks to see the durability of the modified bricks (CSLB). Samples were formulated by mixing laterite, cement, and different percentages of PET (0%, 3%, 5%, and 7%) by volume. The bricks were produced using the M7MI Hydraform standard interlocking block and kept in the shade for a curing period of 28 days. The addition of 3% to 5% PET to the laterite stabilized with 10% cement results in a decrease in both dry and wet compressive strength, which is determined using the Controlab compression machine. However, the obtained results are in concordance with the standards. The thermal conductivity of CSLB, determined using the box method with the EI700 measurement cell, decreases as the PET content of the mixture increases. A decrease in bulk density from 1.67 to 1.58 g/cm3 was observed.

Physical Characterization of Laterite for the Formulation of Structural Concrete

This study presents another approach to the use of laterite as a common construction material for the development of a new type of concrete. Laterites are found all over the world and are used in various ways in road construction as sub-base, base course or wear courses. Being a material consisting in the raw state of sand and gravel, the study addresses its use for the formulation of structural concrete. The physical characterization made it possible to identify three granular classes distributed as follows: 28.26% passing at 80 μm, 32.12% sand (0.08/4 mm) and 39.62% nodule (4/25) mm. The absolute density of the aggregates varies from 2.73 and 2.82 from the sand to the nodules. The absorption rate varies from 3.01% and 5.71% respectively for sand and nodules. The granular compactness of the different granular classes studied varies from 0.580 to 0.630. The formulation of the concrete was made by the method of absolute volumes by varying the W/C ratio from 0.4 to 0.7, N/S from 2.2 to 2.8 and that of the cement dosage from 350 to 450 kg/m3. The results obtained show that the density of the concrete formulated based on these aggregates of lateritic origin have a density which varies between 2000 and 2300 kg/m3. With a cement content of 400 kg/m3, a W/C ratio of 0.4 and N/S of 2.8, concrete based on lateritic aggregates offers better mechanical performance in compression of approximately 21.23 ± 1.24 MPa at 28 days. This strength class obtained allows laterite concrete to be used as structural concrete in the structure of civil engineering works.

Rare Earth Elements Geochemistry of Sheikh-Marut Laterite Deposit,NW Mahabad,West-Azarbaidjan Province,Iran

Laterite deposit at Sheikh-Marut （NW occurred within middle-upper Permian carbonate Mahabad, West-Azarbaidjan province, Iran） rocks. It consists of seven stratiform and/or discontinuous lenticular layers extending over 4.2 km in length and having thicknesses ranging from 3 to 14 m. Mineralogical data show that the ores contain kaolinite and hematite as major and boehmite, diaspore, halloysite, amesite, anatase, and muscovite-illite as minor mineral phases. The computed Ce anomaly values in the ores range from 0.05 to 20.84. Conservative index （e.g., Eu/Eu＊） suggests that this deposit is a product of alteration and weathering of basaltic rocks. Rhythmic increment of EREE values of the ores with approaching to the carbonate bedrocks shows an in-situ occurrence of lateritization processes. Mass change calculations of elements indicate that two competing processes namely leaching and fixation were the major regulating factors in concentration variation of REEs （La-Lu） in this deposit. The obtained results show that pH increase of weathering solutions by carbonate bedrocks, existence of organic matters, and the degree of comlexation with organic ligands played remarkable role in distribution of REEs during lateritization. Further geochemical considerations revealed that secondary phosphates, Mn-oxides and -hydroxides, diaspore, and anatase were the potential hosts for REEs in this deposit.

Adsorption of mercury on laterite from Guizhou Province,China

The adsorption behaviors of Hg(Ⅱ) on laterite from Guizhou Province,China,were studied and the adsorption mechanism was discussed.The results showed that different mineral compositons in the laterite will cause differences in the adsorption capacity of laterite to Hg(Ⅱ).Illite and non-crystalloids are the main contributors to enhancing the adsorption capacity of laterite to Hg(Ⅱ).The pH of the solution is an important factor affecting the adsorption of Hg(Ⅱ) on laterite.The alkalescent environment (pH 7-9) ...

Activation pretreatment of limonitic laterite ores by alkali-roasting using NaOH

Activation pretreatment of Cr-containing limonitic laterite ores by NaOH roasting to remove Cr, Al, and Si, as well as its effect on Ni and Co extraction in the subsequent pressure acid leaching process was investigated. Characterization results of X-ray diffraction （XRD） and scanning electron microscopy/X-ray energy dispersive spectroscopy （SEM/XEDS） show that goethite is the major Ni-bearing mineral, and chromite is the minor one. Experimental results show that the leaching rates of Cr, Al, and Si are 95.6wt%, 83.8wt%, and 40.1wt%, respectively, under the optimal alkali-roasting conditions. Compared with the direct pressure acid leaching of laterite ores, the leaching rates of Ni and Co increase from 80.1wt% to 96.9wt% and 70.2wt% to 95.1wt% after pretreatment, respectively. Meanwhile, the grade of acid leaching iron residues increases from 54.4wt% to 62.5wt%, and these residues with low Cr content are more suitable raw materials for iron making.

Preparation of zeolite NaA for CO_2 capture from nickel laterite residue

Zeolite NaA was successfully prepared from nickel laterite residue for the first time via a fusion-hydrothermal procedure. The structure and morphology of the as-synthesized zeolite NaA were characterized with a range of experimental techniques, such as X-ray diffraction, scanning electronic microscopy, and infrared spectroscopy. It was revealed that the structures of the produced zeolites were dependent on the molar ratios of the reactants and hydrothermal reaction conditions, so the synthesis conditions were optimized to obtain pure zeolite NaA. Adsorption of nitrogen and carbon dioxide on the prepared zeolite NaA was also measured and analyzed. The results showed that zeolite NaA could be prepared with reasonable purity, it had physicochemical properties comparable with zeolite NaA made from other methods, and it had excellent gas adsorption properties, thus demonstrating that zeolite NaA could be prepared from nickel laterite residue.

Preparation of ferronickel from nickel laterite via coal-based reduction followed by magnetic separation

The sticking phenomenon between molten slag and refractory is one of the crucial problems when preparing ferronickel from laterite ore using rotary hearth fulnace or rotary kiln processes. This study aims to ameliorate sticking problems by using silicon dioxide （SiO2） to adjust the melting degree of file briquette during reduction roasting. Thermodynamic analysis indicates that the melting temperature of the slag gradually increases with an increase in the SiO2 proportion （SiO2/（SiO2 ＋ A1203 ＋ MgO） mass ratio）. Experimental validations also prove that the briquette retains its original shape when the SiO2 proportion is greater than 75wt%, and sticking problems axe avoided during reduction. A ferronickel product with 8.33wt% Ni and 84.71wt% Fe was prepared via reductive roasting at 1500~C for 90 min with a SiO2 proportion of 75wt% and a C/O molar ratio of 1.0 followed by dry magnetic separation; the corresponding recoveries of Ni and Fe reached 75.70% and 77.97%, respectively. The micro stxucture and phase txmlsformation of reduced briquette reveals that the aggregation and growth of ferroinckel particles were not significantly affected after adding SiO2 to the reduction process.

Generation process of FeS and its inhibition mechanism on iron mineral reduction in selective direct reduction of laterite nickel ore

Numerous studies have demonstrated that Na2SO4 can significantly inhibit the reduction of iron oxide in the selective reduction process of laterite nickel ore. FeS generated in the process plays an important role in selective reduction, but the generation process of FeS and its inhibition mechanism on iron reduction are not clear. To figure this out, X-ray diffraction and scanning electron microscopy analyses were conducted to study the roasted ore. The results show that when Na2SO4 is added in the roasting, the FeO content in the roasted ore increases accompanied by the emergence of FeS phase. Further analysis indicates that NaeS formed by the reaction of Na2SO4 with CO reacts with SiO2 at the FeO surface to generate FeS and Na2Si2Os. As a result, a thin film forms on the surface of FeO, hindering the contact between reducing gas and FeO. Therefore, the reduction of iron is depressed, and the FeO content in the roasted ore increases.

Application of response surface methodology in optimizaing thesulfation-roasting-leaching process of nickel laterite

Nickel was recovered from nickel laterite using a sulfation-roasting-leaching process and the effects of operation parameters in- cluding acid addition, roasting temperature, and roasting time on nickel extraction and iron dissolution were investigated using response sur- face methodology （RSM）. Two second-order polynomial models of high significance were presented to show the relationship between the responses and the variables. The analysis of variance （ANOVA） showed high coefficients of determination （R2） of 0.894 and 0.980 for the two models, respectively. Optimum areas of 〉-80% Ni extraction and 〈5% Fe dissolution were obtained by the overlaid contours. Verification experiments in the optimum areas were conducted and the results indicate a close agreement with the predicted values obtained from the models.

Effects of Na_2SO_4 on iron and nickel reduction in a high-iron and low-nickel laterite ore

This study investigates the reactions of Na2SO4 and its effects on iron and nickel reduction in the roasting of a high-iron and low-nickel laterite ore through gas composition, X-ray diffraction, and scanning electron microscope analyses. Results showed that a reduction reaction of Na2SO4 to SO2 was performed with roasting up to 600℃. However, no clear influence on iron and nickel reductions appeared, because only a small amount of Na2SO4 reacted to produce SO2. Na2SO4 reacted completely at 1000℃, mainly producing troilite and nepheline, which remarkably improves selective reduction of nickel. Furthermore, the production of low-melting-point minerals, including troilite and nepheline, accelerated nickel reduction and delayed iron reduction, which is attributed to the concurrent production of magnesium magnetite, whose structure is more stable than the structure of magnetite. Reduction reactions of Na2SO4 resulted in weakening of the reduction atmosphere, and the main product of Na2SO4 changed and delayed the reduction of iron. Eventually, iron metallization was effectively controlled during laterite ore reduction roasting, leading to iron mainly being found in wustite and high iron-containing olivine.

Extraction and separation of nickel and cobalt from saprolite laterite ore by microwave-assisted hydrothermal leaching and chemical deposition

Extraction and separation of nickel and cobalt from saprolite laterite ore were studied by using a method of microwave-assisted hydrothermal leaching and chemical deposition. The effects of leaching temperature and time on the extraction efficiencies of Ni2＋ and Co2＋ were investigated in detail under microwave conditions. It is shown that the extraction efficiencies of Ni2＋ and Co2＋ from the ore pre-roasted at 300℃ for 5 h were 89.19% and 61.89% when the leaching temperature and time were about 70℃ and 60 min, respectively. For the separation process of Ni and Co, the separation of main chemical components was performed by adjusting the pH values of sulfuric leaching solutions using a NaOH solution based on the different pH values of precipitation for metal hydroxides. The final separation efficiencies of Ni and Co were 77.29% and 65.87%, respectively. Furthermore, the separation efficiencies of Fe of 95.36% and Mg of 92.2% were also achieved at the same time.

Feasibility of co-reduction roasting of a saprolitic laterite ore and waste red mud

Large scale utilization is still an urgent problem for waste red mud with a high content of alkaline metal component in the future.Laterite ores especially the saprolitic laterite ore are one refractory nickel resource,the nickel and iron of which can be effectively recovered by direct reduction and magnetic separation.Alkaline metal salts were usually added to enhance reduction of laterite ores.The feasibility of co-reduction roasting of a saprolitic laterite ore and red mud was investigated.Results show that the red mud addition promoted the reduction of the saprolitic laterite ore and the iron ores in the red mud were co-reduced and recovered.By adding 35wt%red mud,the nickel grade and recovery were 4.90wt%and 95.25wt%,and the corresponding iron grade and total recovery were 71.00wt%and 93.77wt%,respectively.The X-ray diffraction（XRD）,scanning electron microscopy,and energy dispersive spectroscopy（SEM-EDS）analysis results revealed that red mud addition was helpful to increase the liquid phase and ferronickel grain growth.The chemical compositions＂Ca O and Na_2O＂in the red mud replaced Fe O to react with Si O_2 and Mg Si O_3 to form augite.

A green process for recovering nickel from nickeliferous laterite ores

A novel process was proposed for recovering nickel from nickeliferous laterite ores.First of all,silicon and magnesium were removed from lateritic ore by high concentration sodium hydroxide leaching and carbonation respectively,so as to enrich nickel. Then the method of ammonia carbonate leaching was adopted to recover nickel from the carbonized slag,and the remaining residue was used as a raw material for recovering iron.The effects of temperature,ammonia carbonate concentration,liquid/solid ratio and stirring speed on the recovery of nickel were examined.When the leached residue reacted with ammonia carbonate(6 mol·L- 1)in a ratio of liquid-to-solid of 5-1 at 60℃for 150 min at the stirring speed of 300 r·min- 1,approximate more than 95%nickel was recovered.During the whole process,there was no contamination produced and the chemical raw materials were recycled,thus the process was a green technology that having good social benefit.

Pretreatment study on chloridizing segregation and magnetic separation of low-grade nickel laterites

The chloridizing segregation and magnetic separation of low-grade nickel laterites from Yunnan province of China was investigated.The nickel laterites were characterized by microscopic investigations,using X-ray diffractometry(XRD)and energy dispersive spectrometry(EDS)techniques.The pellets,which were prepared with magnesium chloride and coke as chloride agent and reductant respectively,were heated to a high temperature,and the pellets after cooling were crushed for magnetic separation.A series of experiments were conducted to examine the effect of chlorinating agent dosage,reductant dosage,chloridizing temperature and chloridizing time on enrichment grade of Ni and Co.The results indicate that the four factors have significant effects on the extractions of Ni and Co.The optimum conditions are as follows:the amounts of magnesium chloride and coke are 6%and 2%,respectively,chloridizing temperature is 1 253 K,and chloridizing time is 90 min.Under the conditions,extractions of Ni and Co reach 91.5%and 82.3%,respectively.

Thermal behaviors and growth of reduced ferronickel particles in carbon-laterite composites

The thermal behaviors of single laterite ore and graphite-laterite mixtures were investigated by thermogravimetry （TG）, derivative thermogravimetry （DTG）, and differential thermal analysis （DTA）. Four mass loss steps maximized at about 78, 272, 583, and 826℃ are observed for the laterite ore, representing the vaporization of free water, the dehydroxylation of goethite, the decomposition of serpentines, and the second dehydroxylation of serpentines, respectively. The reduction reactions of the graphite-laterite mixtures start at around 700℃ and can be divided into three major temperature regions. Coal-laterite composites with an addition of 10 wt.% CaO were roasted at 1100-1350℃ for 30 min, and the reduced samples were characterized by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The results indi- cate that the reduction reactions proceed more completely at higher temperatures. The growth of the reduced ferronickel particles is greatly influenced by the roasting temperature, Obvious growth of the reduced ferronickel particles appears with the formation of worm-like crystals for the sample reduced at 1250℃ and spheric particles are observed for the sample reduced at 1300℃. When the reduction temperature increases to 1350℃, the reduced ferronickel particles agglomerate to ferronickel granules of 3-8 mm in diameter. The main elements in the granules include iron, nickel, chromium, carbon, and sulfur, with the content of nickel and that of iron of 9.08 wt.% and 85.21 wt.%, respectively.

Evolution of ferronickel particles during the reduction of low-grade saprolitic laterite nickel ore by coal in the temperature range of 900–1250℃with the addition of CaO–CaF_(2)–H_(3)BO_(3)

The method of producing ferronickel at low temperature(1250–1400℃)has been applied since the 1950s at Nippon Yakin Kogyo,Oheyama Works,Japan.Limestone was used as an additive to adjust the slag composition for lowering the slag melting point.The ferronickel product was recovered by means of a magnetic separator from semi-molten slag and metal after water quenching.To increase the efficiency of magnetic separation,a large particle size of ferronickel is desired.Therefore,in this study,the influences of CaO,CaF_(2),and H_(3)BO_(3) additives on the evolution of ferronickel particle at≤1250℃were investigated.The experiments were conducted at 900–1250℃with the addition of CaO,CaF_(2),and H_(3)BO_(3).The reduction processes were carried out in a horizontal tube furnace for 2 h under argon atmosphere.At 1250℃,with the CaO addition of 10 wt%of the ore weight,ferronickel particles with size of 20μm were obtained.The ferronickel particle size increased to 165μm by adding 10 wt%CaO and 10 wt%CaF_(2).The addition of boric acid further increased the ferronickel particle size to 376μm,as shown by the experiments with the addition of 10 wt%CaO,10 wt%CaF_(2),and 10 wt%H_(3)BO_(3).