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Abstract Ammonia is widely used in chemical industries to produce fertilizers, plastics, and explosives, resulting in high ammonia levels in industrial waste. Natural zeolites have been used as adsorbents for wastewater treatment because of their unique adsorption properties. These natural zeolites hold great potential in several applications. The characteristic properties of natural zeolite depend on the methods of surface modifications and their availability and location. This review is descriptive consolidation of the adsorption behavior of zeolites on the batch study with a detailed analysis of parameters like dosage, contact time, stirring speed/time, pH, the effect of ammonia concentration, and temperature that determine the capabilities of natural zeolite. Also, it covers the different techniques adopted for their surface modifications and applications with other properties and structures. All the critical parameters and physical properties have been elaborately discussed with the points for their improvement, emphasizing the impact of zeolite modifications. This enunciates a descriptive study of the evolution of natural zeolites from the past to the current developments and their applications.

This study investigated proximate composition and heavy metal concentration in wheat flour samples gathered from five districts of Haryana and Madhya Pradesh. The sample of Panchkula, Rohtak, Palwal, Dadri, Sirsa, Bhind, Neemuch, Bhopal, Khargone, and Anuppur are referred to as HR1, HR2, HR3, HR4, HR5, MP1, MP2, MP3, MP4, and MP5 respectively. The parameters such as moisture, total ash, acid insoluble ash, gluten, crude fibre, alcoholic acidity, and granularity were determined following Indian Standard (IS) 1155:1968. Several heavy metals such as lead (Pb), chromium (Cr), cadmium (Cd), arsenic (As), and mercury (Hg) in wheat flour, water, and soil were also determined by using inductively coupled plasma optical emission spectroscopy (ICP-OES). Results show that moisture, ash, acid insoluble ash, gluten, crude fibre, and alcoholic acidity ranged from 6.9 to 12.6 %, 1.1 to 1.89 %, 0.049 to 0.092 %, 9.4 to 12.4 %, 0.4 to 2.4 %, and 0.11 to 0.18 % respectively. Overall, all the samples were found to have acceptable values for proximate content, except alcoholic acidity, which exceeded the permissible limit. Heavy metal studies inferred that Pb content in wheat flour samples ranged from 0.38 to 3.5 μg/g while Cr content ranged from 1.9 to 6.2 μg/g. Heavy metal concentration in soil increased in the following order: Cr>Pb>As>Cd>Hg. Principal component analysis (PCA) and Hierarchical cluster analysis (HCA) indicated the Hg-Cd cluster, suggesting the same source of origin. Bioaccumulation factor (BAF) values obtained for all the samples are <1, indicating that heavy metal concentration in the wheat flour is less than in the soil. The total target hazard quotient (TTHQ) was greater than 1 for all wheat samples, indicating high health risk upon consumption.

Geopolymer materials, alternatives to cement that are synthesized using industrial byproducts, have emerged as some of the leading champion materials due to their environmentally friendly attributes. They can significantly reduce pollution by utilizing a plethora of waste products and conserving natural resources that would otherwise be used in the production of conventional cement. Much work is being carried out to study geopolymers’ characteristics under different conditions. Here, a geopolymer derived from fly ash (FA) was synthesized using a combination of sodium silicate and potassium hydroxide (KOH) (2.5:1 ratio) as an alkali activator (AA) liquid. The FA/AA ratios were optimized, resulting in distinct geopolymer samples with ratios of 1.00, 1.25, 1.50, and 1.75. By adjusting the contribution of alkaline liquid, we investigated the impacts of subtle changes in the FA/AA ratio on the morphology and microstructure using X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) techniques. The FESEM analysis illustrated a mixed matrix and morphology, with the sample with a ratio of 1.00 displaying consistently fused and homogenous morphology. The XRD results revealed the prevalent amorphous nature of geopolymer with a few crystalline phases of quartz, sodalite, hematite, and mullite. An electrical study confirmed the insulating nature of the geopolymer samples. Insulating geopolymers can provide energy-efficient buildings and resistance to fire, hurricanes, and tornadoes. Additionally, using KOH as a part of the alkali activator introduced a less-explored aspect compared to conventional sodium hydroxide-based activators, highlighting the novelty in the synthesis process.

Fly ash (FA)-based geopolymer was prepared using sodium hydroxide and sodium silicate (in 2.5ratio) as an alkali activator liquid (AL). The condition of FA/AL was optimized for achieving 1.00, 1.25, 1.5, and 1.75 ratios by varying the alkali concentrations, which are referred to as GP1, GP2, GP3, and GP4, respectively. The influence of slight variations in the FA/AL ratio on microstructure, morphology, functional groups, and composition was investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), X-ray fluorescence (XRF), and Fourier transform infrared spectroscopy (FTIR). FESEM detected a homogeneous fused matrix of fly ash and alkali activator solution up to 1.5 ratios; GP3 showed a dense morphology. FTIR confirmed that the formation of aluminosilicate gel induced a shift in the T–O (T = Si or Al) asymmetric stretching band, nearing a lower frequency. XRD showed an amorphous structure with phases, including quartz, mullite, hematite, and sodalite. The thermogravimetry and differential thermal analysis (TGA–DTA) indicated that the geopolymer samples were thermally stable. The electrical study concluded that the geopolymer possessed insulating properties.