Alkaline Wastewater Research Articles

Influence of industrial effluent treatment ettringite on the compressive and tensile strength and microstructure of soil-cement mixtures

It is increasingly important to find solutions for the problem of the aluminium anodising industry which generates a large amount of acid and alkaline wastewater, composed of high amounts of phosphates, sulphates, nitrates and aluminium. The sulphate removal trough ettringite precipitation is a simple process and involves a low-cost operating. The ettringite can be also formed during the cement hydration in soil-cement mixtures which causes several damages such as expansion. However, the effect of ettringite on the compressive strength, tensile strength and microstructure have few studies. This paper presents a novel experimental study on the influence of the industrial effluent treatment ettringite in resistance and microstructure of soil-cement mixtures. Experimental tests were performed using natural soil, soil mixed with 5% and 6% of cement and soil mixed with 5% and 6% of cement and ettringite for each material. The resistance of the materials was evaluated by unconfined compressive strength and indirect tensile strength, after 3, 7 and 14 days of cure. Additionally, several characterization tests and microstructure analysis were performed. Regarding the experimental results, the compressive strength and tensile strength decreases about 75% and 85%, respectively, when ettringite was added in soil-cement mixtures. The microstructure of natural soil, soil-cement and soil-cement-ettringite mixtures shows that the addition of cement and ettringite, simultaneously, increases the ettringite crystal formation mainly because the cement functions as a source of sulfate ions contributing with the formation of more crystals. Experimental results indicate that the incorporation of ettringite in soil-cement mixtures is not suitable for geotechnical applications.

Study of molecular mechanism and extraction performance evaluation for separation of phenolics from alkaline wastewater through synergistic extraction

ABSTRACT Phenols were a kind of pollutant in coal chemical wastewater with high concentration and difficult to decompose and have a significant impact on the subsequent biochemical treatment of the wastewater. In addition, phenols were a kind of weak electrolytes that partially dissociation oxidation under weakly alkaline conditions, making recovery more difficult. In order to solve this problem, phenols were extracted from weak alkaline wastewater with a synergistic solvent. First, the interaction between solvents and phenols and the solvent effect of solvents were calculated by quantum chemistry and the synergistic extractant cyclohexanone/1-pentanol was determined to have significant advantages. Moreover, the synergistic extractant was further analyzed through independent gradient model based on Hirshfeld partition analysis, atoms in molecule topology analysis, electrostatic potential analysis. Results indicated that the synergistic extract can provide multiple hydrogen bond interactions with phenol due to the double action sites of the C=O group of ketone and the -OH group of alcohol. In addition, the efficacy of the extractant was validated by multistage extraction, indicating partial dissociation oxidation of hydroquinone to benzoquinone under weakly alkaline conditions, with removal rates of 99.5% and 99.2% for phenol and hydroquinone, respectively. In general, the synergistic extractant can effectively remove phenols.

Application of electro oxidation process for treating wastewater from petrochemical with mixed metal oxide electrode

Petrochemicals require a large volume of water for their operation, which results in the production of a large volume of wastewater. Treatment of petrochemical wastewater is an important process before discharging it into the environment. This research examines the treatment of real petrochemical wastewater using the electrochemical oxidation process. Direct anodic oxidation is an effective advanced electrochemical oxidation process (AEOP), with different electrodes using a parallel plate electrochemical reactor. Four types of real wastewater were received from different petrochemical units were treated by AEOP. Real wastewater samples with chemical oxygen demand (COD) concentrations ranging from 20,450 to 52,300 mg/l. The main goal of this research is to make electrodes of Mixed Metal Oxide (MMO), which can reduce the treatment time and electricity consumption for oxidation, greater stability of the surface of the electrodes. Investigation of the rate constant kinetics shows that high COD removal efficiency can be achieved following the pseudo-second order reaction rate (R2 > 98%). When the wastewater pH is less than 5, COD removal efficiency is higher and the treatment process will be successful, which succeeded in removing 79% COD, but in alkaline wastewater, COD reduction efficiency was not satisfactory. The electricity consumption for 79% removal during 6 min was 117 kWh/m3. As a result, due to the very short time of the process (6 min), it can be used as one of the pre-treatment steps of petrochemical wastewater with acidic pH.

Chemical, physical, and sensory properties of nixtamalized oat tortillas

AbstractBackground and ObjectivesWhile alkaline nixtamalization has historically been used for corn, this process may have application in other cereals. Drawbacks to wider use include the lengthy steep time, as well as the volume of alkaline wastewater produced. This study evaluated a novel, waste‐effluent‐free nixtamalization process for oat (Avena sativa) masa, and compared properties of oat masa and tortillas prepared with 1%, 1.5%, and 2% lime, with and without steeping.FindingsA minimal‐water‐addition, 45‐min simmering process, without steeping, was effluent‐free, and produced oat tortillas comparable to those produced using a traditional overnight steep. The pH increased significantly with increasing lime content (r = .982). Consumer overall‐liking scores did not significantly differ across treatments, though appearance scores were significantly higher for 2% lime samples (p < .05), which were significantly darker and more yellow, based on L* and b* values. Masa adhesiveness means ranged from 1.49 to 1.52 N, with no significant differences between the no‐steep treatments. Higher lime addition (1.5%–2%) in the no‐steep process significantly improved tortilla flexibility, based on extensibility and rollability scores, though tortilla rupture force did not vary significantly across treatments. Tortilla rollability scores at 3‐days were lowest ( = 1.1 + 0.31, indicating less cracking) for the 1.5%–2% lime no‐steep treatments, which were significantly better than the steeped treatment ( = 3.7 + 0.48). Consumers rated the steeped sample as significantly less flexible. B‐vitamins were negatively impacted by increasing lime, while calcium increased significantly with lime addition.ConclusionsThe no‐steep, effluent‐free nixtamalization process produced oat tortillas with good masa and tortilla texture, which were not significantly different in consumer liking than tortillas produced via a traditional process.Significance and NoveltyThis research suggests nixtamalization can be applied to other grains in a shorter, environmentally friendly process, with broader commercial applicability.

Efficient removal and transformation of Cr(VI) from alkaline wastewater to form a ferrochromium spinel multiphase via a modified ferrite process

Chromium-containing wastewater causes serious environmental pollution due to the harmfulness of Cr(VI). The ferrite process is typically used to treat chromium-containing wastewater and recycle the valuable chromium metal. However, the current ferrite process is unable to fully transform Cr(VI) into chromium ferrite under mild reaction conditions. This paper proposes a novel ferrite process to treat chromium-containing wastewater and recover valuable chromium metal. The process combines FeSO4 reduction and hydrothermal treatment to remove Cr(VI) and form chromium ferrite composites. The Cr(VI) concentration in the wastewater was reduced from 1040 mg L−1 to 0.035 mg L−1, and the Cr(VI) leaching toxicity of the precipitate was 0.21 mg L−1 under optimal hydrothermal conditions. The precipitate consisted of micron-sized ferrochromium spinel multiphase with polyhedral structure. The mechanism of Cr(VI) removal involved three steps: 1) partial oxidation of FeSO4 to Fe(III) hydroxide and oxy-hydroxide; 2) reduction of Cr(VI) by FeSO4 to Cr(III) and Fe(III) precipitates; 3) transformation and growth of the precipitates into chromium ferrite composites. This process meets the release standards of industrial wastewater and hazardous waste and can improve the efficiency of the ferrite process for toxic heavy metal removal.

Unraveling the atomic-scale mechanism of interfacial alkali ion close packing in nano glassy fibers driven by CO2-mediated attraction.

The poor alkali resistance of nano-glassy fiber (NGF) hinders its application in aggressive alkaline environments like cement and alkaline wastewater. This study introduced a potential strategy to enhance the alkali resistance of NGF based on the distinct atomic-scale interactions between CO2 molecules and NGF ions at high temperatures. The short-range structure in the NGF-CO2 system was elucidated through the pair distribution functions and coordination numbers of ion-oxygen pairs and second-nearest-neighbor ion-ion pairs. High-mobility Na ions were observed to exhibit a strong interaction with CO2, penetrating through the melt skeleton and accumulating at the interface. The enrichment of Na ions as network modifiers enhanced the alkali resistance of NGF, with the maximum thickness of the enrichment layer reaching ∼5 Å at 1173 K. These findings present a straightforward production approach for alkali-resistant NGF, not requiring additional costly materials or processes.

Environmentally responsible production of lime from recycled gypsum and weakly alkaline wastewater

Benefits associated the treatment of wastewater from a returnable glass bottle-washing process as applied in this study. Our result transforms wastewater treatment into resource recovery, producing lime in an environmentally responsible manner.

“Gray Carbon” in Sewage Treatment Plants: A Neglected Carbon Sink

This study introduces the concept of “gray carbon,” emphasizing its critical role in carbon sequestration in sewage treatment. By focusing on recalcitrant dissolved organic carbon (RDOC) in sewage effluents and its subsequent transformation in marine environments, we underscore the significant impact of sewage-derived organic carbon on the efficiency of carbon sequestration. Through analysis of carboxylic-rich alicyclic molecules, this study illuminates the convergence in the molecular compositions of RDOC across various aquatic systems. Dark-culture experiments reveal marked variations in the microbial community structures of the aforementioned molecules, indicating that these changes may play an important role in the degradation and subsequent transformation of organic matter in marine environments. These insights lay the groundwork for advancing technologies designed to enhance wastewater alkalinity, which will improve the sustainability of wastewater treatment and preserve marine ecosystems. Enhancing sewage alkalinity can influence microbial processes and chemical equilibria, potentially affecting the formation and accumulation of gray carbon. Further investigation is necessary to understand the potential effect of alkalinity enhancement on the microbial communities and biochemical pathways involved in gray carbon formation. Our findings support the integration of gray carbon strategies into broader carbon neutrality initiatives, providing a scientific and technological blueprint for enhancing global carbon management and mitigating climate change.

Strong acid-mediated Ca2+ extraction–CO2 mineralization process for CO2 absorption and nano-sized CaCO3 production from cement kiln dust: Simultaneous treatment of CO2 and alkaline wastewater

Increasing yearly stockpiles of cement kiln dust (CKD) and the associated high landfilling cost require innovative solutions to utilize CKD. This study proposes a strong acid-mediated extraction–mineralization process that utilizes CO2. The process comprises the extraction of Ca2+ from CKD using strong acids, mineralization of CO2 using extracted Ca2+ and alkaline wastewater, and production of Ca carbonate. High Ca2+ leaching efficiency, high Ca2+ extraction efficiency, and high-purity nano-sized CaCO3 production from CKD were achieved under normal operating conditions in an in-situ strong acid solution. The process feasibility was primarily tested via an individual extraction process using aqueous HCl and HNO3 solutions from typical CKD and mineral carbonation experiments using Ca(OH)2 and alkaline wastewater obtained from the extraction process. The process had a Ca2+ leaching efficiency of 94.73%, Ca2+ extraction efficiency of 93.54%, and CaCO3 yield of 1.45 ton/ton CKD in the aqueous HCl solution. Polymorphism and crystal structure analyses showed that CaCO3 obtained after CO2 mineralization was mainly present as calcite. Alkaline wastewater acted as a pH buffer, enhanced the reactivity with CO2, accelerated the conversion of CO2(g) to CO32-(aq), and acted as an accelerator that promoted the nucleation growth of CaCO3 by OH- ions during the mineralization process. The effect of the nucleation and growth of CaCO3 on the particle and crystallite size is highly dependent on the system pH. These results can be applied to CO2 utilization processes by industrial by-products.

Ammonia release characteristics during desulfurization wastewater evaporation: Mechanisms and implications

This study investigated the mechanisms of ammonia release during desulfurization wastewater evaporation and its potential environmental impacts. A single droplet evaporation device (SDD) assessed the wastewater evaporation and ammonia release characteristics. Approximately 8.5 % of ammonia was released during the free water evaporation period (0–35 s). As the droplet underwent shell inflation-deflation and core-shell drying, the remaining ammonia was mainly released due to increased vapor pressure and poor thermal stability of ammonium salts. The wastewater properties, especially pH value, greatly influenced the release of ammonia. Alkaline wastewater exhibited a significantly higher ammonia release rate. Ammonia migration and transformation were studied in a 600 MW power plant. Approximately 9.2–11.7 % of ammonia was released, while the rest was retained in solid form within the evaporation product. Characterization techniques and DFT simulations showed that the released NH3 probably combines with fly ash due to the water vapor, HCl, SO3, and other acidic gases in the flue gas. Risk analysis suggested that ammonia release during evaporation would not significantly increase ammonia concentration in flue gas or hinder fly ash comprehensive utilization. However, when handling desulfurization wastewater with high-concentration ammonia, it was essential to consider the potential corrosion of downstream equipment caused by released ammonia.

Electrocatalytic Degradation of Rhodamine B on the Sb-Doped SnO2/Ti Electrode in Alkaline Medium.

To realize efficient electrocatalytic degradation of organic compounds in alkaline wastewater, an Sb-doped SnO2/Ti electrode was fabricated and employed for the removal of Rhodamine B (RhB), and the electrocatalytic oxidation performance of this electrode was assessed in an alkaline medium. In an alkaline solution (pH 11), the complete fading of 50 mg·L-1 RhB could be achieved after 150 min of degradation, the removal efficiency of the chemical oxygen demand reached 56.1% at 300 min, and the degradation process of RhB followed the pseudo-first-order kinetic model very well. Under the attack of hydroxyl radicals, partial RhB was degraded to low-molecular-weight organic acids through N-demethylation and the destruction of the conjugated chromophore. Various techniques including scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and cycle voltammetry were used to examine the changes in the morphology and structure, as well as the activity of the Sb-doped SnO2/Ti electrode before and after use. The Sb-doped SnO2/Ti electrode could be reproduced in batches, and each electrode was reused up to eight times without a significant decrease in degradation ability; the leaching amount of antimony was significantly lower than the national emission standard. The electrocatalytic oxidation of the dye wastewater sample was also performed with the desired results, indicating that electrochemical oxidation is a very promising technology for the treatment of alkaline dye wastewater using a Sb-doped SnO2/Ti electrode.

Ionization‐engineered two‐dimensional confined channels in GO membranes for highly efficient OH− separation

AbstractOH− sieving membranes provide a valuable means for treating alkaline effluents but their development presents several challenges. In this study, the concept of ionization engineering is applied to two‐dimensional (2D) laminated membranes to facilitate OH− separation. This concept is demonstrated through the stacking of the self‐designed sulfonated graphene oxide (SGO) nanosheets to fabricate 2D membranes. The SGO membranes enhance synergistically the OH− dialysis coefficients and separation factors when treating simulated NaOH/Na2WO4 alkaline wastewater, compared with the performance of 2D GO membranes and commonly adopted polymeric cation exchange membranes. Furthermore, the separation factor achieved by the SGO membranes is considerably higher than that of most of the existing alkali recovery membranes. Results of molecular dynamics simulations indicate that the high efficiency of OH− separation in the 2D SGO confined channels is attributable to dehydration effects and intensified electrostatic repulsion. Overall, this research provides an alternative strategy for achieving rapid OH− sieving through the ionization of 2D confined channels.

Enhanced conversion from H2O2 to 1O2 on Cu–N centers: Investigation of mechanisms and application in alkaline wastewater treatment

Heterogeneous Fenton-like systems using H2O2 as an oxidant have been extensively investigated in acidic and neutral conditions, but usually, they become ineffective under alkaline conditions. In this study, a cuprous graphitic carbon nitride material (Cu–CN) was prepared that can generate singlet oxygen (1O2) from H2O2. The results demonstrate that at pH 11, 95 % of 50 mg/L p-chlorophenol (4-CP) can be effectively eliminated within 120 min. Through semi-quantitative analysis and density functional theory calculations, it has been confirmed that 1O2 is the dominant reactive oxygen species in this system under alkaline conditions. The main pathway for 1O2 generation involves the formation of a complex between ·O2– and Cu(II)-N sites, and the subsequent intramolecular electron transfer. To enhance the stability and separation performance of this catalyst, polyethylene glycol (PEG) was employed as a binder to combine Cu–CN with Fe3O4. The terminal hydroxyl groups in PEG were cross-liked by metals, thus forming a solid and magnetic composite (CuFe@PEG). Compared to Cu–CN, CuFe@PEG exhibited remarkable performance with 93 % retention of its original capacity for 4-CP removal at pH 11. Furthermore, after seven cycles, the degradation efficiency only decreased by 6.36 %. This study introduces a novel approach for utilizing Fenton-like reactions in treating alkaline wastewater.

Co single-atom C2N3 activates peroxymonosulfate for efficient degradation of sulfamethoxazole at 4 °C: A combined experimental and density functional theory study

The Fenton-like reactions for antibiotic degradation become very slow at low temperatures. To overcome this inadequacy, we prepared a rare CxNy allotrope, C2N3, by pyrolysis of HNO3 pretreated melamine and loaded with ultrahigh-density Co single atom (SA) to activate peroxymonosulfate (PMS) to remove sulfamethoxazole (SMX). Results showed that the removal rate of SMX reached 100 % at 4 °C within 8 min. The Co/C2N3-650 + PMS system achieved excellent degradation efficiency for simulated wastewater experiments and various interference factors. The catalyst could efficiently degrade a variety of antibiotics, and achieved more efficient degradation rate in alkaline wastewater. Electron paramagnetic resonance (EPR) measurements and quenching tests confirmed the primary role of singlet oxygen (1O2) in SMX degradation with PMS. Density functional theory (DFT) calculation verified the binding energy of CoN3 site and activation pathway for the different oxygen sites of PMS. The linear sweep voltammetry (LSV) and chronopotentiometry analysis revealed that the electrons of PMS were transferred to the CoN3 sites to form SO5•- intermediates, and proved the generation of 1O2 via the SO5•- self-reaction. This work reveals a new mechanism for the formation of 1O2 and opens up novel approach for SA heterogeneous catalysts in advanced oxidation processes (AOPs).

NiCo layered double hydroxides/NiFe layered double hydroxides composite (NiCo-LDH/NiFe-LDH) towards efficient oxygen evolution in different water matrices

Engineering robust non-noble metal electrocatalysts towards efficient impure water (e.g., seawater, wastewater) oxidation is a prospective approach to achieve carbon neutrality via accelerating green hydrogen energy development. Herein, a NiCo layered double hydroxides (LDH)/NiFe LDH composite (NiCo-LDH/NiFe-LDH) was developed for oxygen evolution reaction (OER) via a hydrothermal process-electrodeposition method. The optimal NiCo-LDH/NiFe-LDH-30 composite only needed an overpotential (η) of 240 mV to drive 100 mA/cm2 in alkalized freshwater, with a low Tafel slope of 16.6 mV/dec and good stability for over 90 h. Further analyses suggested that the strong interface interaction between NiCo-LDH and NiFe-LDH accelerated the oxygen gas bubble evolution and boosted interfacial charge transfer, and the formed built-in electric field and higher oxidation state species (metal oxyhydroxides) contributed to the high intrinsic catalytic activity. The NiCo-LDH/NiFe-LDH-30 composite also held excellent OER activities in different impure water environments, including alkaline 0.5 M NaCl solution (η100 = 333 mV), alkaline lake water (η100 = 345 mV), and alkaline wastewater treatment plant (WWTP) effluent (η100 = 320 mV). More importantly, the potential effects of Cl− and CO32− in impure water were revealed during the OER process. This work elaborates on the role of built-in electric field and the strong coupling interaction in composite catalysts, which pave the way for the design of cost-effective catalysts with excellent adaptability in different water environments.

Valorization of phenolic compounds from brewery wastewater: Performances assessment of ultrafiltration and nanofiltration process with application of HPLC coupled with antioxidant analysis tool

Phenolic-rich brewery alkaline wastewater sustainable valorization with membrane technology was investigated. Intensified process of preselected ceramic 15 kDa ultrafiltration and 200 Da nanofiltration membranes was studied at pH 4, 6.5, 10 and 13.5 to prospect the best operation conditions of phenolic compounds (PC) recovery and water reclamation process regarding fouling inclination, productivity and selectivity performances. Flux-limiting phenomena propensity according to pH were investigated. HPLC coupled with online antioxidant capacity innovative analysis was used to assess PC selectivity behavior and its subsequent impact on antioxidant properties of concentrated wastewater. Flux-limiting phenomena consisted of PC, carbohydrates and proteins pore blocking and cake layer during ultrafiltration and was corroborated to pH acidity. Osmotic pressure due to ions concentration polarization was predominant during nanofiltration and was lower during pH 4 and 13.5 due to membrane characteristics. PC selectivity by ultrafiltration and nanofiltration membranes was determined with compounds size and chemistry, along with pH effect on molecules and membrane charges. The chemical structure of single PC led to differential segregation through the valorization process, and thus to modification of the antioxidant profile of concentrated wastewater. pH 13.5 showed controlled fouling development and advantageous selectivity and productivity performance, and nanofiltration yielded concentrated PC retentate for resource recovery and clarified permeate for water and alkalis reclamation.

Three-dimensional fluorinated pyrazinium-based cationic organic polymers with high charge density for enhanced ReO4− removal

Ultrafast separation of hazardous and radioactive anions from strongly alkaline nuclear wastewater is urgently needed for both the public health and environment, but also extremely challenging. Herein, we report a 3D fluorinated pyrazinium-based cationic organic polymer (TBPM-Fpz) with high charge density for ultrafast and selective removal of ReO4−. Using fluorinated pyrazine as the linker and rigid tetraphenylmethane as the building block, a high charge density and relatively hydrophobic diamond-like topology skeleton of TBPM-Fpz was constructed, which is beneficial to improve the affinity for ReO4− and promote thorough exposure of active sites. Batch sorption experiments revealed that TBPM-Fpz is a rare example that can integrate ultrafast sorption kinetics (equilibrium within 3 min), high capacity (833.01 mg g−1), and excellent selectivity towards ReO4− (92.34% in 1000 times excess of SO42−) in one adsorbent. In addition, TBPM-Fpz achieve high ReO4− removal efficiency in simulated Savannah River Site High-Level Waste stream (95.32%, solid-to-liquid ratio: 40:1) and simulated Hanford Low Activity Waste wastewater (89.76%, solid-to-liquid ratio: 1:1). Experimental and computational results indicate that the superior performance is attributed to fluorination that increases charge density and decrease the steric hindrance. This study shows the enormous potential of fluorinated cationic organic polymer for enhanced ReO4− removal from strongly alkaline wastewater, providing valuable insights into designing high-performance cationic organic polymers for alkaline nuclear waste treatment.

Physicochemical characterization and antioxidant capacity of popcorn nejayote

The pursuit of reusing agribusiness residues towards decreasing their environmental impact has led to the study of its components to know their possible applications. The nejayote is the alkaline wastewater of different food products of nixtamalized corn. This study characterized the physicochemical properties of popcorn nejayote (NP) and determined its total phenolics content (TP) and antioxidant capacity by standard synthetic assays (ABTS and DPPH) and physiologically relevant ones (reducing power -RP-, hydroxyl radical scavenging activity -OH-, and iron chelation IRON). NP antioxidant capacity determined by ABTS, and DPPH methods were 387.9±0.7 and 419.3±2.9 mM Trolox equivalents (mM TE)/mL, respectively. The NP showed 296% RP compared to a control solution of coumaric acid (0.1 M). Also, the NP was obtained at 143% IRON compared to a control solution of caffeic acid (0.1 M). In the case of OH, values ranged from 27% to 45% compared with control solutions. TP was 0.26±0.006 μg gallic acid equivalents/mL (mg GAE/mL). Pearson's correlation analysis found that TP is correlated to the OH, IRON, and DPPH, while IRON activity correlates with OH and ABTS. And finally, OH correlated with DPPH. To the best of our knowledge, this study is NP's first antioxidant capacity report.

Effective reduction and recovery of As(III) and As(V) from alkaline wastewater by thiourea dioxide: Efficiency and mechanism.

For alkaline wastewater with high arsenic concentration, the traditional lime precipitation inevitably produces large amounts of hazardous waste. Herein, a heat-activated reduction method employing thiourea dioxide (TDO) as the reductant was proposed to efficiently remove and recover As(III)/As(V) from alkaline wastewater in the form of valuable As(0). More than 99.9% of As(III)/As(V) (2-400mM) were reduced to As(0) with a high purity of more than 99.5 wt% by TDO within 30min. The highly reductive eaq- and SO2- radical generated during TDO decomposition contribute to the arsenic reduction, and the contribution ratios of eaq- and SO2- radical were estimated to be approximately 57.6% and 42.4% for As(III) removal and 62.2% and 37.8% for As(V) removal, respectively. The arsenic reduction was greatly improved by increasing pH and temperature, which could accelerate the cleavage of C-S bond in TDO for the eaq- and SO2- formation. The presence of dissolved oxygen, which can not only scavenge eaq-/SO2- but also directly oxidize SO22-, had a negative effect on the arsenic removal. The presence of CO32- slightly suppressed the arsenic removal due to the eaq- scavenging effect while SiO32-, PO43-, Cl-, SO42- and NH4+ had negligible effects. The proposed method was a potential technology for the efficient removal and reduction of arsenic in alkaline wastewater.

Utilization of Various Industrial Wastes in Ordinary Concrete Under Normal Manufacturing Conditions

The main objective of the present work is to evaluate using alkaline wastewater from pot factories (recycled NaOH solutions with variant concentrations and pH values) along with waste powders possessing pozzolanic properties, such as supplementary cementitious materials and stone waste dust in concrete under normal manufacturing conditions. An extensive analysis of the chemical components and the physical properties of the used materials was achieved. Both supplementary cementitious materials and stone waste dust materials were used as 0%, 10%, 20%, or 30% partial cement replacements using either tap water or alkaline wastewater to make samples for physical, mechanical, and microstructure testing. Thermodynamic modeling was used to evaluate the effect of the flushed alkaline industrial water and the powders on the hydration products. The results showed an increase in the workability of the mixes made with alkaline wastewater, an increase in water absorption for samples made with alkaline wastewater at the age of 28 days, and a relative decrease in compressive strength at 3 and 28 days, respectively. Despite the reduction in mechanical strength, most samples made with alkaline wastewater and 10%, 20% supplementary cementitious materials, or stone waste dust materials gave an accepted concrete grade. The microstructure analysis showed a slight change in pores distribution, pores values, and hydration products at 3 and 28 days. The thermodynamic analysis provided insight into data on the effect of supplementary cementitious materials, stone waste dust materials, and alkaline wastewater on hydration products. Finally, the combination of these wastes in concrete production showed satisfactory conclusions.