Sands Processing Research Articles

Preparation process and performance study of desert sand autoclaved bricks

Desert Sand Autoclaved Brick(DSAB) represents a novel type of building wall material. To investigate the performance of this wall material in the high-intensity cold regions of Xinjiang, this study, based on the(GB/T 11945–2019) "Autoclaved sand-lime solid brick and solid block" standard, explores the impact of varying lime content, forming pressure, autoclaving time, and autoclaving temperature on compressive strength. The aim was to determine an appropriate preparation process for DSAB that meets meets MU15-grade requirements. Additionally, experimental research was conducted on the micro-pore structure, freeze-thaw durability, and carbonation performance of the manufactured MU15-grade DSAB. Furthermore, microscopic analysis methods were employed to analyze the mechanisms behind the changes in the strength of the DSAB throughout the various experiments. The research findings are as follows: The optimal preparation parameters for producing MU15-grade DSAB are a forming pressure of 20 MPa, an autoclaving time of 8 h, and an autoclaving temperature of 180 ℃. Mercury intrusion porosimetry(MIP) revealed that DSAB has a total porosity of 38.19%, an average pore diameter of 55.86 nm, total pore volume of 0.175 mL/g, and total pore area of 12.56 m2/g. The majority of pore spaces consist of harmful and more harmful pores. DSAB exhibits favorable freeze-thaw durability. After 30 freeze-thaw cycles, the strength loss rate is only 7.0%, and the mass loss remains within 1%. After carbonation, the newly formed CaCO3 and SiO2 fill the brick's pores, transforming pre-existing harmful large pores into harmless tiny pores. After complete carbonation, the carbonation coefficient reaches 1.17.

Electrocatalytic activation of peroxomonosulfate (PMS) under aerobic condition for the remediation of oil sands process water: Insight into one-pot synergistic coupling of PMS electro-activation and heterogeneous electro-Fenton processes

Alkaline industrial effluents possess a different challenge during treatment by advanced oxidation processes due to the reduction in redox potential of hydroxyl radical (•OH) in basic media. Herein, electrocatalytic peroxomonosulfate activation (EC-PMS), which synergistically couples an early-stage PMS electro-activation (E-PMS) with subsequent heterogeneous electro-Fenton oxidation (HEF) catalyzed by Fe-modified biochar (BC-Fe) was investigated for enhanced degradation and mineralization of organics in oil sands process water (OSPW). The EC-PMS was first studied for the degradation of surrogate naphthenic acids (NAs) (5-phenylvalveric acid, (PVA)) as a synthetic process water and complete degradation of 50 mg L−1 PVA solution was achieved within very short treatment time (0.5 h) with excellent mineralization (>70 % TOC removal) in 6 h. The efficiency of EC-PMS for PVA degradation was affected by the applied current density, PMS, and catalyst dosage. The organic degradation, electroparamagnetic resonance spectrometry, quenching and chemical probe experiments showed that sulfate radical (SO4•−) generated by E-PMS was the dominant radical oxidant for the degradation of PVA, contributing over 93 %, whereas •OH produced from BC-Fe decomposition of electrogenerated H2O2 in HEF was responsible for the mineralization of the organic solution at the later stage of the coupled process. The EC-PMS showed excellent reusability and was effective for the treatment of real OSPW, achieving complete degradation of real NAs in OSPW and relatively good mineralization of the water. Analysis of the EC-PMS treated OSPW did not simulate any response during the bioactivity assay test using a macrophage cell line, indicating the complete detoxification of the water.

Ozone in the boreal forest in the Alberta Oil Sands Region

Abstract. Measurements of ozone were made using an instrumented tower and a tethersonde located in a forested region surrounded by oil sands production facilities in the Athabasca Oil Sands Region (AOSR). Our observations and modeling show that the concentration of ozone was modified by vertical mixing, photochemical reactions, and surface dry deposition. Measurements on the tower demonstrated that when winds are from the direction of anthropogenic emissions from oil sand extraction and processing facilities, there is no significant increase in ozone mixing ratio compared to when winds are from the direction of undisturbed forest. This suggests that ozone is destroyed by reaction with NOx from oil sands extraction operations (as well as NO resulting from photolysis of NO2). Vertical gradients of ozone mixing ratio with height were observed using instruments on a tethered balloon (up to a height of 300 m) as well as a pulley system and two-point gradients within the canopy. Strong gradients (ozone increasing with height near 0.35 ppb m−1) were measured in the canopy in the evening and overnight, while morning and daytime gradients were weaker and highly variable. A 1D canopy model was used to simulate the diurnal variation of the in-canopy gradient. Model results suggest an ozone dry deposition velocity between 0.2 and 0.4 cm s−1 for this location. Sensitivity simulations using the model suggest that the local NO concentration profile and coefficients of vertical diffusivity have a significant influence on the O3 concentrations and profiles in the region.

Fingerprinting construction sand-supply networks for traceable sourcing

Globally increasing demand for construction sand needs to be met with transparent and responsible supply-networks. Currently, there are few scalable methods for tracing construction sand distribution without direct observation. He wee examined sand “fingerprinting” as a tool to trace construction sand supply-networks from “source to sink” in a case study from Texas, USA. Both natural bulk major element and optical petrography fingerprints are preserved through construction sand processing and transport such that sand can be tied back to its original mining source even at the final point of distribution. Additionally, we developed an image analysis model called sandID that is ~90% effective at determining the original mining source of sand in the study area. Our results demonstrate that sand fingerprinting, has untapped potential to support traceability and certification schemes and to support monitoring and enforcement in areas where there are concerns about illegal, illicit or simply unknown construction sand sourcing.

The Effect of Leaching Time on ZrO<sub>2</sub> Synthesis through Alkali Fusion and Acid Leaching

Zircon (ZrSiO4) is one of Indonesia's most abundant mineral reserves that have yet to be fully utilized since zircon mine production in Indonesia is only 110.000 tons/year while Australia produces zircon up to 500.000 tons/year. Indonesia has 167 million tons of zircon sand reserves, especially in West Kalimantan. One of the most efficient methods of zircon sand processing in terms of energy use and environmental pollution is the alkali fusion of NaOH. This study used zircon sand with NaOH, a stoichiometric ratio of 1:4 (excess 1.5), to be roasted in a muffle furnace at 600°C for 120 min. The following process is washing the frit with water, and the frit is dissolved with aquades with ratio frit: H2O=1g:10 ml at 30°C and stirring 300 rpm for 60 min. The frit leaching solution is filtered to obtain Na2ZrO3. The water-wash product is leached using HNO3 as the leaching agent with the ratio of water-wash product: HNO3=1:5, the acid concentration is 6 M, at 90°C, agitation use 260 rpm with the variation of time 60, 120, 180, 240, and 300 minutes. The pregnant leach solution is deposited with NH4OH and calcinated. According to the results of this experiment, the optimum time to obtain high Zr extraction is 240 minutes. This research produced single-phase zirconia with a cubic crystal structure containing 91.23% ZrO2 and 1.18% SiO2.

Study on screening process and segregation mechanism of wet sand and gravel particles based on discrete element method

Study on screening process and segregation mechanism of wet sand and gravel particles based on discrete element method

Polygenic gold mineralization in quartz-pebble formations on the Takyr-Kaljir site of the Southern Altai, East Kazakhstan Region

Purpose. The research purpose is to study the forms of gold occurrence in the Takyr graben alluvial-proluvial deposits in order to develop a low-waste resource-saving processing technology. Methods. At the first stage, in the course of field studies, the geological structure of the site is specified, samples are taken for mineralogical-technological analysis, which includes the following procedures: studying granulometric and mineral composition of detrital material; fractional gravitational beneficiation of the source material; fractional beneficiation of material pre-processed in the autogenous mill (AG mill); studying free (native) and bound gold in beneficiation products, their quantitative assessment. The samples are processed under the three-stage scheme using an autogenous mill for sample preparation. Findings. For the first time, the geological structure of the site has been specified with the identification of the deposits in the Turangi and Tuzkabak suites within its boundaries, as well as granulometric and petrographic composition of gold-bearing deposits, and the specifics of gold bearing. The detrital material, represented by quartz with a sharply subordinate amount of quartzite, quartz diorites and jasperoids, is practically identical in all fractions. Originality. For the first time, various types of gold mineralization have been identified in placer sands: clastogenic, newly-formed hypergene, newly-formed hydrothermal and residual. Fractional beneficiation makes it possible to estimate the gold content in each fraction and gravitational beneficiation products, as well as the ratio of free and bound native gold in different fractions. The largest amount of free native gold has been revealed in fractions of -0.25 + 0.1 mm (60%) and -0.074 + 0.044 mm (~40%). Gold is high-grade (96.5%) with an admixture of silver and iron. Together with gold, ilmenite, zircon, scheelite, native bismuth, as well as barite, galena, sphalerite, and dolomite have been identified. Practical implications. The research results make it possible to reassess the prospects of similar objects, to adjust the scheme and methodology for processing stream-sediment samples, to solve the issues of productive sand processing technology, as well as to improve the efficiency of geological exploration and eliminate the “underestimation” of gold deposits. The results obtained can be recommended for implementation by both domestic and foreign organizations specializing in the exploration and mining of gold deposits.

Life cycle triple bottom line sustainability assessment of coal mine overburden sand versus river sand

Crushed coal mine overburden (OB) waste rock has been found to be a promising, robust, and reliable alternative of river sand as fine aggregate in several construction applications. The processing of OB to application ready specification requires preprocessing that may cause negative environmental impacts. The environmental impacts have been quantified in previous studies. However, the economic and social impacts were not addressed, which has created confusion among practitioners and policy makers to take initiatives in promoting OB sand as a sustainable geomaterial considering the triple bottom line (environmental, economic, and social) approach. The present study uses Quantitative Assessment of Life Cycle Sustainability (QUALICS) framework that incorporates Analytical Hierarchy Process (AHP) and Integrated Value Model for Sustainable Assessment (MIVES) for integrated triple bottom line (environmental, economic, and social) assessment of processing of OB sand versus typical river sand. OB sand is found to cause relatively less impact in 6 out of 10 indicators in environmental assessment. High direct cost is neutralized by the monetized environmental benefit, direct benefits, and indirect benefits. The social score rating of OB sand is found to be relatively higher than river sand for all four criteria of social assessment (individual, community, socio-environmental, and socio-economic). The integrated sustainability indices for OB sand and river sand were determined to be 0.60 and 0.33, respectively, when equal weightage was given to all three triple bottom line aspects. These results clearly demonstrate that OB sand is a more sustainable option compared to river sand. Furthermore, conducting a sensitivity analysis with increased weightages assigned to the economic and social aspects reaffirmed that OB sand can be a sustainable replacement to river sand as fine aggregate.

Processing of Alluvial Deposit Sands with a High Content of Copper and Nickel Using Combined Enrichment Technology

The aim of the present research was to examine the process of bioleaching and the application of a combined process for the recovery of copper and nickel from industrial sand deposits. The investigated sample of sands finer than 0.1 mm in size contained 0.32% Ni and 0.22% Cu. Industrial sands were processed by bioleaching in flasks on a thermostatically controlled shaker. In addition, sand roasting experiments were carried out with ammonium sulfate. An attempt was also made to use a combined process, including low-temperature roasting of the sands mixed with ammonium sulfate, water-leaching of the roasted mixture, and subsequent biological after-leaching of the residue. In the process of roasting the industrial sands in a mixture including ammonium sulfate at a temperature of 400 °C, more than 70% of the non-ferrous metals were recovered. We examined the possibility of recovering non-ferrous metals using a combined process including low-temperature roasting of industrial sands and the additional recovery of non-ferrous metals by bioleaching using the Acidithiobacillus ferrivorans bacterial strain, which was found to increase the recovery of non-ferrous metals to up to 90%.

Improving the Characteristics of Less Active Geopolymer Binders Utilizing Ground Granulated Blast-Furnace Slag under Different Curing Conditions

In the current study, the influence of substitution of ground granulated blast-furnace slag (GGBFS) on the characteristics of less active geopolymer binders, including pumice and the waste material produced during the washing process of sand in aggregate industries (waste soil), is investigated. The aforementioned materials were examined individually and in hybrid form. In the hybrid mixes, less-active materials (pumice and the waste soil) were replaced with GGBFS at levels of 25%, 50%, and 75%. The evaluated properties consisted of compressive strength, modulus of rupture, sorptivity, rapid chloride ion migration coefficient, and the content of water absorption. Moreover, the effects of different curing conditions on the properties were investigated. The results indicate that partial replacement of the waste soil and pumice with GGBFS leads to enhanced durability and mechanical characteristics owing to the higher reactivity of GGBFS. The mixture denoted as P25S75 (with 75% GGBFS and 25% pumice) exhibited the best durability properties, surpassing even the S100 mixture (with 100% GGBFS). Substituting the waste soil with GGBFS had a greater enhancing effect compared to the mixtures containing the pumice mixes.

Effect of grain size distribution on the shear properties of sand

In this study, we investigated the effect of particle size distribution on the shear properties of sand. Direct shear tests were conducted using four types of sand samples with different particle size distributions obtained from standard sand produced by Xiamen ISO Co. Ltd. The results show that the influence of particle size distribution on the internal friction angle was significant. Typically, the internal friction angle increases with increasing the coefficient of non-uniformity (Cu) and decreasing the curvature coefficient (Cc). The discrete element results show that the initial particle size distribution significantly affects the porosity, coordination number, and particle slide fraction. In addition, the grey relation analysis revealed that the sliding fraction and coordination number have the greatest correlation with the internal friction angle. The research results of this study help to understand the changes in particle contact, internal stress, and particle sliding during the shear failure process of sand.

Experimental study on the reaction process and engineering characteristics of marine calcareous sand reinforced by eco-friendly methods

Calcareous sands are important building materials in ocean engineering. In order to ensure the stability of the island under the actions of wave and current, the marine calcareous sand was reinforced by two eco-friendly methods (Microbial and Enzyme induced carbonate precipitation, MICP and EICP). The concentrations of calcium and bacteria, shear wave velocity, global hydraulic conductivity, penetration resistance and microscopic characteristics of each test were evaluated systematically. The normalised shear wave velocity in EICP treated samples were smaller than those of MICP treated sand, but the response of EICP was faster at the same duration. The global hydraulic conductivity exhibited different degrees (46% of MICP and 28% of EICP) of exponential reductions with the increase of the time in dry environment. It exhibited less degrees (33% of MICP and 18% of EICP) of liner reductions in underwater environment. The cementation products of MICP in calcareous sand were mainly spherical calcium carbonate in both dry and underwater environments, and rhombohedral calcium carbonate also appeared in dry environment, leading to higher penetration resistance in P1-M than P2-M. For EICP-treated calcareous sands, calcium carbonate crystals in dry environment were mainly rhombic, and loose eggshell-like morphologies were formed in underwater environment. MICP was more suitable than EICP for the reinforcement of marine calcareous sands in underwater environments.

Coping with Pregnancy Loss through Sandtray Therapy

This case study explores the use of sandtray therapy interventions with an adult that experienced pregnancy loss. A description of the case will discuss how the use of the sand tray facilitated a client's processing of trauma and grief in the aftermath of an early pregnancy loss, becoming pregnant again, and coping with a new pregnancy after loss. Illustrations of the sand tray setup, prompts, themes, and processing questions will be provided.

Study of the Adsorption Efficacy of Cr(III) on a Metal Oxide-Based Material Derived from the Quartz Sand Enrichment Process

In the present study, the efficacy of chromium removal from water media was studied. For this purpose, a metal oxide based material, derived from the enrichment process of quartz coastal sand was used as possible adsorbent of chromium (III) ions. Following additional modification of the adsorbent, the effect of operational parameters including pH, contact time and Cr(III) concentration were studied according to one-factor-at-a-time procedure. Adsorption efficacy was assessed by the measurement of the remaining chromium concentration in solution, after adsorption. Atomic absorption spectroscopy technique, with flame atomization was used for the determination of chromium concentration in solution. Obtained results revealed that selected material exhibited higher adsorption efficacy in alkaline solution (pH = 6-9). The maximum removal efficacy (>93%) was achieved after 180 minutes of contact time, with an adsorbent dosage of 5 g/L and initial chromium concentration 20 mg/L. The adsorption process for Cr(III) follow the Freundlich isotherm and gives high correlation coefficient R². Calculations performed based on the Langmuir isotherm showed that the maximum adsorption efficiency of Cr³⁺ in the natural metal-oxide material has resulted 10 mg/g or 10000 μg/g. Pseudo second order reaction kinetics has provided a realistic description for removal of Cr(III) from solution with high correlation coefficient R² of (0.999). The adsorption isotherms were better described by the Freundlich equation (R² = 0.934). Adsorption of trivalent chromium ions onto selected material followed the pseudo second order model (R² = 0.996). Hence, the residual materials derived from the enrichment processes of quartz sand can be used as alternative adsorbent for the removal of trivalent chromium ions from aqueous solutions.

Aeolian sand cover affects the soil hydrothermal state and permafrost degradation on the Qinghai-Tibet Plateau

Aeolian sand significantly affects permafrost degradation, but the effect of the aeolian sand on the permafrost on the Qinghai-Tibet Plateau remains unknown. The sand layer thickness is critical to its role. However, little quantitative research has been conducted on the effect of the sand layer thickness on its role. In this study, using CoupModel, we investigated the differences in the impact of the aeolian sand cover on the hydrothermal state of permafrost with 20 different sand layer thicknesses (10 ∼ 200 cm, 10 cm increment) and analyzed the mechanisms that explain the different impacts. The results reveal that the active layer is where the aeolian sand has the most impact on the permafrost. The aeolian sand layer accumulates precipitation into the soil below the sand, thereby significantly drying the shallow soil layer of the current stratum. Moreover, the thicker the sand layer, the more water accumulates in the underlying soil layer. In the middle-upper active layer, the initial soil heat storage, soil heat flow interception, and liquid water and ice contents govern the soil temperatures that increase in cold seasons and decrease in warm seasons as the sand layer thickens. Near the bottom of the active layer, the initial soil heat storage and soil heat flow interception control the soil temperatures that increase in cold seasons but fluctuate between sand layer thicknesses of 50 cm, 70 cm, and 120 cm in warm seasons as the sand layer thickens. Permafrost degradation is enhanced by sand layers thinner than 150 cm and retarded by sand layers thicker than 150 cm, respectively. The thermal state, soil properties, and accumulation process of the aeolian sand also contribute to this effect of the aeolian sand on the permafrost. In the plateau aeolian deserts, the sparse vegetation promotes permafrost degradation and the thinner seasonal snow cover protects permafrost. Moreover, under the different climate during the geological history period, the island or discontinuous permafrost might be formed due to the pluvial-radiation talik caused by the thicker sand layer or dunes.

Enhanced bitumen extraction from oil sands using CO2-responsive surfactant combined with low-salinity brine: Toward cleaner production via CO2 utilization

With a recent concern on more sustainable production, oil sands as an affordable energy resource requires more efficient and cleaner technology to extract bitumen from its deposits. Recent study conceptualized the combination of greener bitumen recovery and CO2 utilization, which shows promising potential. Using CO2-responsive surfactants that could ‘switch’ the bitumen-water interfacial behavior, oil-water separation process can be greatly improved, although its workability in bitumen aeration stage and co-presence with brines are not yet fully examined. In the current study, influence of a combination of CO2-responsive surfactant and NaCl brine fluids to bitumen liberation and aeration stages were investigated. Two interfacial phenomena (i.e., bitumen-water interfacial tension and bitumen-water-substrate contact angle) were studied as dominant parameters to oil sands processing. Although an ultra-low interfacial tension at high mixture concentration (6 mM surfactant + 500 mM NaCl) promises an advantage for bitumen extraction via a spontaneous bitumen pinch-off, some bitumen residual was left unproduced on substrate. While the low-salinity brine at the same surfactant concentration (6 mM surfactant + 10 mM NaCl) resulted in a much-reduced bitumen-substate contact area, which could practically enhance bitumen liberation. Furthermore, CO2-responsive surfactant suggests a good switchability in such a high-salinity environment for bitumen-water demulsification, owing to the CO2-induced acidification. In aeration stage, CO2 bubble was found a greater ‘attachability’ to bitumen surface compared to typical air bubble. This observation suggests a promising CO2 utilization as an alternative flotation gas carrier for bitumen aeration. The findings in the current study provide fundamental guidance on bitumen extraction process enhanced by both surfactant and brine fluids. The study also confirms a holistic improvement for the whole extraction process with CO2 utilization toward a cleaner production that couples both climate action and affordable energy sustainable goals.

Influence of Traditional Food Processing Systems on Food Safety, Chemical Compositions, and Functional Properties of Pumpkin (Cucurbita pepo L) Seed Flour

Background: Plant foods contain almost all of the essential mineral and organic nutrients for human, as well as several unique organic phytochemicals that have been linked to the promotion of good health. This study investigated the influence of traditional food processing systems on the food safety, chemical compositions, and functional properties of pumpkin (Cucurbita pepo L) seed flour.
 Methods: Fresh mature pumpkin fruits were procured from the laboratory. The pumpkin seed was divided into three different portions and subjected to traditional sand toasting, germination, and processing into flour. The samples were analyzed for proximate composition, minerals, heavy metals, vitamins, functional properties, and microbial safety.
 Results: The result of proximate composition analyses revealed that raw and traditionally processed pumpkin seed flour had 33.75-39.63% protein, 43.65-36.36% fat, 7.38-5.89% moisture, 4.85-6.04% ash, 1.89-2.25% fiber, and 5.94-14.49% carbohydrate. The mineral and heavy metal content were in the range of 7.17-4.13 mg/100 Iron, 117.88-221.55 mg/100 g Potassium, 7.41-9.01 mg/100 g Calcium, 45.67-55.65 mg/100 g Phosphorus, 0.89-4.67 mg/100 g Iodine, and 7.39-6.33 mg/100 g Zinc. The toxic/deleterious elements values for Hg, Pb, As, and Cd were 0.018-0.004 mg/100 g; 0.021–0.062 mg/100 g, 0.013–0.092 mg/100 g, and 0.0011-0.0051 mg/100 g, respectively. Cyanide, Nitrate, Phytate, and Oxalate contents of the pumpkin seed flour were 0.72-0.32 mg/100 g, 2.77–1.00 mg/100 g, 35.56–14.56 mg/100 g, and 0.073–0.030 mg/100 g, respectively. An appreciable amount of vitamins (Beta-carotene, vitamin C, and thiamine) were recorded with excellent functional properties. The microbial count was within the limit of national and international standards showing the processed pumpkin seed flour to be safe. 
 Conclusion: It can be concluded that subjecting pumpkin seeds to traditional processing methods enhanced their nutritional properties and food safety quality. Therefore, adopting this traditional processing approach can be used in rural community nutrition and nutrition in emergency feeding programs in developing countries.

Structural characterization, in vivo toxicity and biological activity of two new pyro-type diterpenoid alkaloids derived from 3-acetylaconitine

ObjectiveThe transformations that occur in diterpenoid alkaloids during the process of sand frying for Chinese herbal medicine preparation have yet to be clarified. This study investigated the structural changes that take place in 3-acetylaconitine during a simulation of heat-processing and evaluated the toxicity and biological activity of the pyrolysis products. MethodsThe diterpenoid alkaloid 3-acetylaconitine was heated at 180 °C for 15 min to simulate the process of sand frying. The pyrolysis products were separated using column chromatography, and their structures were investigated using high-resolution electrospray ionization mass spectroscopy and nuclear magnetic resonance spectroscopy. Further, in vivo cardiotoxicity and acute toxicity of 3-acetylaconitine and its pyrolysis products were compared, and the aconitine-induced arrhythmia model was employed to evaluate the antiarrhythmic effect of the pyrolysis products. ResultsTwo new diterpenoid alkaloids, pyroacetylaconitine and 16-epi-pyroacetylaconitine, a pair of epimers at C-16, were isolated. After comparing the structures of these compounds, possible transformation pathways were proposed. Compared with the prototype compound, 3-acetylaconitine, the cardiotoxicity and acute toxicity of the heat-transformed products were significantly decreased. In the biological activity assay, the two pyrolysis products exhibited an effective increase in ventricular premature beat latency, a reduction in the occurrence of ventricular tachycardia, as well as an increase in the rate of arrhythmia inhibition, implying strong antiarrhythmic activity. ConclusionCompared with 3-acetylaconitine, its pyrolysis products displayed lower toxicity and good antiarrhythmic effects; thus, they have potential for being developed into antiarrhythmic medicines.Please cite this article as: Wang YJ, Wang Y, Tao P. Structural characterization, in vivo toxicity and biological activity of two new pyro-type diterpenoid alkaloids derived from 3-acetylaconitine. J Integr Med. 2023; 21(3): 302–314.

Study on the Adsorption Characteristics of Calcareous Sand for Pb(II), Cu(II) and Cd(II) in Aqueous Solution

The adsorption characteristics of calcareous sand for heavy metals Pb(II), Cu(II) and Cd(II) have been studied by batch testing in this study. The influence of the solid–liquid ratio, initial pH0 value, ionic strength, reaction time, temperature and initial concentration on adsorption has been investigated. Test results indicate that the initial pH and the solid–liquid ratio have a significant influence on the removal efficiency. At T = 30 °C, r = 1.0 g/L, and C0 = 1000 mg/L and for 12 h of reaction, the removal efficiencies of Pb(II), Cu(II) and Cd(II) are 97.6%, 88.15% and 65.72%, respectively. The adsorption quantity is more than 80% of the maximum adsorption quantity within 60 min, and the equilibrium adsorption can be reached within 120 min. The pseudo-second-order kinetic model is suitable to simulate the dynamic adsorption process of calcareous sand, and the isothermal process is found to obey the Langmuir model. Calcareous sand has a very high adsorption capacity for Pb(II), Cu(II) and Cd(II), with a maximum adsorption quantity Qm reached 1052.95 mg/g, 1329.84 mg/g and 1050.56 mg/g, respectively. Thermodynamic test results indicate that the adsorption process is spontaneously exothermic and that low temperature is favorable to the adsorption reaction.

Identification Fluidity Method to Determine Suitability of Weathered and River Sand for Constructions Purposes

At present, in order to comply with the development of the “the Belt and Road Initiatives”, the country is accelerating the pace of construction and increasing the demand for construction river sand. However, the quality of construction river sand is uncontrollable, and its shape is very similar to that of weathered sand. Therefore, using inferior weathered sand and mixed sand as inferior substitute sand in the market is prohibited, resulting in an increase in the difficulty coefficient of quality control of concrete fine aggregate in actual projects. This lays hidden dangers for the construction quality of the project. It is urgent to improve the quality control, testing, and detection process of river sand. Due to the long-term weathering of weathered sand, its density is small, and there are many pores, which leads to the material’s water absorption rate is higher than that of standard sand and river sand during fluidity tests. This paper takes this as a breakthrough point, reveals the variation law of fluidity loss under different variables, and explores a method for effectively screening low-quality sand and gravel. Through the silt content test (screening and washing method), the low-quality sand is preliminarily screened out, the mortar ratio is designed, and the fluidity test is carried out to compare the difference in fluidity loss of different types of mortar; determine the loss threshold range (mobility loss ≤ 15 mm) according to the mobility test results of the control group, and determine the qualification standard by comparing the measured mobility loss of the unknown sample with the loss threshold range. When the mobility loss is within the loss threshold range, the sample is qualified river sand. Otherwise, it is weathered sand or chowder sand. This method establishes a complete detection scheme for distinguishing weathered sand and river sand through mud content tests and mobility loss tests, solves the difficult problem of river sand quality control in engineering applications, and effectively eliminates the phenomenon of using low-quality weathered sand as river sand in the sand and gravel material market, thus avoiding congenital defects in concrete homogeneity.