Environmental assessment of utilizing date palm ash as partial replacement of cement in mortar

Investigating the Potential Use of Date Kernel Ash (DKA) as a Partial Cement Replacement in Concrete

The palm and date sector is one of the most important sectors in Saudi Arabia. The total number of fertile palm trees in Saudi Arabia is about 31 million. In the production of pitted dates, date molasses, date paste, and date confectionery, a considerable number of date kernels are usually discarded as waste. This study reports experimental investigations conducted to evaluate the potential of waste date kernel ash (DKA), obtained by the calcination of date pits at 800 °C, as a partial cement replacement in concrete. DKA has low silica oxide and does not qualify as a pozzolanic material. The effect of DKA partially replacing the cement and acting as a filler material in concrete was investigated, and its properties were compared with two pozzolanic materials, fly ash (FA) and natural pozzolan (NP). Twelve concrete mixes in which cement was replaced with different proportions of calcined DKA (5%, 10%, 15%, 20%, and 30%), NP (10%, 20%, and 30%), and FA (10%, 20%, and 30%) were investigated in the experimental program. The properties of DKA, FA, and NP concrete mixes were evaluated in fresh and hardened states, including the heat of hydration, mechanical characteristics, and thermal properties. The results show that replacing cement with 5% date kernel ash increases the compressive strength by 0.42%, 3.2%, and 2.5% at 3, 7, and 28 days, respectively, while the 28-day compressive strength decreases by 2.4%, 5.4%, 16.3%, and 26.69% when the cement is replaced with 10%, 15%, 20%, and 30% DKA, respectively. Date kernel ash concrete mixes with 10%, 20%, and 30% replacement levels demonstrated higher compressive and tensile strengths and lower thermal conductivity, density, and workability when compared to natural pozzolan and fly ash. DKA is a promising partial cement replacement material; nevertheless, additional research is required to assess the durability of DKA in concrete.

Electrolytic manganese residue disposal based on basic burning raw material: Heavy metals solidification/stabilization and long-term stability

Solidification/stabilization (S/S) is an option for the treatment of electrolytic manganese residue (EMR). Basic burning raw material (BRM) could successfully solidify/stabilize EMR, though heavy metals S/S mechanism and long-term stability remain unclear. Herein, Mn²⁺ and NH₄⁺ S/S behavior, hydrated BRM and S/S EMR characterization, Mn²⁺ long-term leaching behavior, phase and morphology changes for long-term leaching were discussed in detail to clarify these mechanisms. Mn²⁺ and NH₄⁺ leaching concentrations as well as pH value in S/S EMR were respectively 0.02 mg/L, 0.68 mg/L and 8.75, meeting the regulations of Chinese standard GB 8978-1996. Long-term stability of EMR was significantly enhanced after S/S. Mn²⁺ leaching concentration, Mn²⁺ migration, Mn²⁺ cumulative release, Mn²⁺ apparent diffusion coefficient and conductivity of EMR reduced to 0.05 mg/L, 5.5 × 10^-6 mg/(m²·s), ~ 9 mg/m², 6.30 × 10^-15 m²/s and 435 μs/cm. Mechanism studies showed that the hydration of BRM forms OH^-, calcium silicate hydrate gels (C-S-H) and ettringite. Therefore, during S/S process, NH₄⁺ was escaped as NH₃, Mn²⁺ was solidified/stabilized as tephroite (Mn₂SiO₄), johannsenite (CaMnSi₂O₆) and davreuxite (MnAl₆Si₄O₁₇(OH)₂), and Pb²⁺, Cu²⁺, Ni²⁺, Zn²⁺ were solidified/stabilized by C-S-H and ettringite via substitution and encapsulation. This study provides a good choice for EMR long-term stable storage.

Synthesis and SWOT analysis of date palm frond ash-Portland cement composites

Environmental threats posed by the cement manufacturing industry and agro-industrial waste discharge have shifted the direction of research towards building sustainable construction without compromising the technical merits of the developed binders. Date palm trees are one of the highest numbers of trees in the world whose generated wastes can be beneficially recycled and reused by the concrete industry. In this study, ordinary Portland cement (OPC) and date palm frond ash (DPFA)-based binders were synthesized by varying ratio of DPFA/(OPC + DPFA) between the range of 0 to 0.3 at an interval of 0.1. Both base materials were characterized by physical, chemical, and thermal techniques. The developed binders were assessed by flow, setting time, and compressive strength up to 360 days of curing. Scanning electron microscopy (SEM) was performed to complement the strength results. It is postulated that the DPFA/(OPC + DPFA) ratio of up to 0.2 outperforms the DPFA-free binder in terms of the overall performance. The properties of binders were negatively affected by the total precursor composition ratio of CaO/SiO₂ and Al₂O₃/SiO₂ below 2.06 and 0.18, respectively. The optimum synergy of OPC-DPFA resulted in superior microstructural density attributed to the uniform skeletal framework of gel products. Strengths, weaknesses, opportunities, and threats analysis of the use of DPFA in cementitious materials showed that there is a high potential for its use in terms of sustainability and economic benefits. However, various weaknesses and threats associated with the use of DPFA as a cementitious material need to be resolved.

Properties and Interfacial Bonding Enhancement of Oil Palm Bio-Ash Nanoparticles Biocomposites

The effect of incorporating different loadings of oil palm bio-ash nanoparticles from agriculture waste on the properties of phenol-formaldehyde resin was investigated in this study. The bio-ash filler was used to enhance the performance of phenol-formaldehyde nanocomposites. Phenol-formaldehyde resin filled with oil palm bio-ash nanoparticles was prepared via the in-situ polymerization process to produce nanocomposites. The transmission electron microscope and particle size analyzer result revealed that oil palm bio-ash nanoparticles had a spherical geometry of 90 nm. Furthermore, X-ray diffraction results confirmed the formation of crystalline structure in oil palm bio-ash nanoparticles and phenol-formaldehyde nanocomposites. The thermogravimetric analysis indicated that the presence of oil palm bio-ash nanoparticles enhanced the thermal stability of the nanocomposites. The presence of oil palm bio-ash nanoparticles with 1% loading in phenol-formaldehyde resin enhanced the internal bonding strength of plywood composites. The scanning electron microscope image revealed that phenol-formaldehyde nanocomposites morphology had better uniform distribution and dispersion with 1% oil palm bio-ash nanoparticle loading than other phenol-formaldehyde nanocomposites produced. The nanocomposite has potential use in the development of particle and panel board for industrial applications.

Sandcastle worm-inspired phytic acid and magnesium oxychloride cement copolymerization for performance enhancement

The development of magnesium oxychloride cement (MOC) can convert wastes in the potash industry into valuable products and reduce CO₂ emission. The use of acid radicals has the potential to enhance the water resistance of MOC. However, because of the internal stress formed during the crystallization process, the occurrence of cracks accompanied by a significant decrease in the mechanical properties is inevitable. Inspired by the sandcastle worm and organic-inorganic copolymerization, a novel strategy was proposed, which employed phytic acid (PA) to copolymerize with phase 5 crystals to reduce the internal stress and prevent crack generation. XPS and TG-DSC analyses revealed that organic-inorganic copolymers were successfully produced. Furthermore, the compressive strength (CS) and water resistance of MOC-PA were significantly enhanced. The enhanced properties were associated with the coordination bonds and high tension of the rigid rings in phytic acid, which was sufficient to overcome the internal stress. Additionally, the repeated hydrolysis of rod-like phase 5 generated a gel-like phase from the outside inward, enhancing their water resistance. Compared with MOC-0, MOC-0.6 showed a 17.8% increase in CS and a 102.3% increase in water resistance. The microscopic mechanisms of the enhanced CS and water resistance of high-performance greener cements were proposed.

Recycling hazardous textile effluent sludge in cement-based construction materials: Physicochemical interactions between sludge and cement

The textile industry produces a large amount of textile effluent sludge (TES). Many studies have explored the potential use of TES in cement-based materials. However, the physicochemical interactions between the TES and ordinary Portland cement (OPC) have rarely been studied. In this study, the effects of increasing dosage (0-20% by OPC) of TES on the performance of OPC-TES blends were investigated in terms of hydration progress, mechanical strength, microstructure evolution and metal leachability. The results showed that TES markedly delayed the OPC hydration at the early age, and increasing dosages of TES decreased the portlandite content at 7 and 28 days' age. Compared to the reference, the OPC-TES mortar exhibited seriously degraded mechanical strength; when using 20% TES, the decrease in compressive and flexural strength reached up to 71% and 42% respectively at the age of 28 days. Scanning electron microcopy and mercury intrusion porosimetry found the inclusion of TES introduced more weak interfaces in the cement mortar, thus increased the total porosity especially the macropores. But leachability tests revealed all the toxic metals in the TES were stabilized after the incorporation of OPC and exhibited very low metal mobility in the OPC-TES mortar, which posed no environmental risk.

Date palm ash-MgAl-layered double hydroxide composite: sustainable adsorbent for effective removal of methyl orange and eriochrome black-T from aqueous phase

Date palm ash (DPA) and MgAl-layered double hydroxide (LDH) composites were synthesized by the co-precipitation method and characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), X-ray diffraction (XRD), and Brunauer-Emmett-Teller (BET). The DPA-MgAl-LDH (DPA/MgAl) composites were employed for the removal of methyl orange (MO) and eriochrome black-T (EBT) from aqueous phase. Incorporation of 33.33% (w/w) DPA into the layers of MgAl increased the surface area from 44.46 to 140.65 m²/g, which leads to the improved adsorption performance. The maximum adsorption capacity of DPA/MgAl (1:2) at 298 K was 242.98 and 425.16 (mg/g) for MO and EBT, respectively. The adsorption data of dyes were adequately fitted by a pseudo-second-order and Langmuir isotherm model. The composite showed excellent reusability performance up to three cycles. Addition of DPA into MgAl-LDH resulted in an effective low-cost adsorbent for decontamination of dyes from wastewater. Graphical abstract ᅟ.