Sulfur Oxidation Research Articles

Feasibility study of a process for the reduction of sulfur oxides in flue gas of fluid catalytic cracking unit using the riser reactor

In this work, a new process for achieving the recovery of elemental sulfur by utilizing a fluidized catalytic cracking (FCC) riser reactor for SOx treatment (FCC-DeSOx) is proposed. The process leverages the high temperatures and hydrocarbon concentrations in the FCC riser reactor to convert SOx into H2S. Subsequently, H2S, along with the cracked gas, is processed downstream to produce sulfur. Thermodynamic analysis of the key reduction reactions in the FCC-DeSOx process revealed that complete conversion of SOx to H2S is feasible in the dry gas (hydrogen-rich) prelift zone, as well as the upper and lower zones of the riser, upon achieving thermodynamic equilibrium. Experimental studies were conducted to replicate the conditions of these reaction zones using a low concentration of hydrogen gas as the reducing agent. Through process optimization, investigation of the minimum reaction time, and kinetic studies, the potential of this method for the complete reduction of SOx was further confirmed.

The role of halophyte-induced saline fertile islands in soil microbial biogeochemical cycling across arid ecosystems

Halophyte shrubs, prevalent in arid regions globally, create saline fertile islands under their canopy. This study investigates the soil microbial communities and their energy utilization strategies associated with tamarisk shrubs in arid ecosystems. Shotgun sequencing revealed that high salinity in tamarisk islands reduces functional gene alpha-diversity and relative abundance compared to bare soils. However, organic matter accumulation within islands fosters key halophilic archaea taxa such as Halalkalicoccus, Halogeometricum, and Natronorubrum, linked to processes like organic carbon oxidation, nitrous oxide reduction, and sulfur oxidation, potentially strengthening the coupling of nutrient cycles. In contrast, bare soils harbor salt-tolerant microbes with genes for autotrophic energy acquisition, including carbon fixation, H2 or CH4 consumption, and anammox. Additionally, isotope analysis shows higher microbial carbon use efficiency, N mineralization, and denitrification activity in tamarisk islands. Our findings demonstrate that halophyte shrubs serve as hotspots for halophilic microbes, enhancing microbial nutrient transformation in saline soils.

Yearly variations of water-soluble ions over Xi'an, China: Insight into the importance contribution of nitrate to PM2.5

Water-soluble inorganic ions (WSIIs) in PM2.5 play an important role in the formation of air pollution, which in turn affects climate change and human health. The formation pathways and factors influencing WSIIs have received extensive attention. Here, we analyzed the contents of nine WSIIs in PM2.5, collected from 2015 to 2021 in Xi'an City, China, with the aim of investigating long-term atmospheric pollution changes. Sulfate (SO42−), nitrate (NO3−), and ammonium (NH4+) together contributed to 66.8%–88.1% and Ca2+ accounted for 5.1%–13.1% of total WSIIs. The relative content of SO42− exhibited a gradually decreasing trend (from 49.80% in 2015 to 29.98% in 2021), whereas NO3− was increased in the same time period (from 13.96% in 2015 to 29.92% in 2021). In addition, the nitrogen oxidation rate showed an annual increase in this period, whereas the sulfur oxidation rate decreased, and their fitted curves intersected in 2019. The key finding of this study is that the air pollution pattern in Xi'an has changed from sulfate-dominated to nitrate-dominated particles, as evidenced by the feature importance results of the random forest model. We propose that more attention should be paid to vehicle emissions and road dust as pollution sources. Overall, the findings of this study serve as a useful reference to aid relevant authorities in devising more effective policies for controlling PM2.5 pollution at its source.

Oxyplasma meridianum gen. nov., sp. nov., an extremely acidophilic organotrophic member of the order Thermoplasmatales.

A mesophilic, hyperacidophilic archaeon, strain M1T, was isolated from a rock sample from Vulcano Island, Italy. Cells of this organism were cocci with an average diameter of 1 µm. Some cells possessed filaments. The strain grew in the range of temperatures between 15 and 52 °C and pH 0.5-4.0 with growth optima at 40 °C and pH 1.0. Strain M1T was aerobic and chemoorganotrophic, growing on complex substrates, such as casamino acids, trypticase, tryptone, yeast and beef extracts. No growth at expenses of oxidation of elemental sulphur or reduced sulphur compounds, pyrite, or ferrous sulphate was observed. The core lipids were glycerol dibiphytanyl glycerol tetraether lipids (membrane spanning) with 0 to 4 cyclopentane moieties and archaeol, with trace amounts of hydroxy archaeol. The dominant quinone was MK-7 : 7. The genome size of M1T was 1.67 Mbp with a G+C content of 39.76 mol%, and both characteristics were well within the common range for Thermoplasmatales. The phylogenetic analysis based on 16S rRNA gene sequence placed the strain M1T within the order Thermoplasmatales with sequence identities of 90.9, 90.3 and 90.5% to the closest SSU rRNA gene sequences from organisms with validly published names, Thermoplasma acidophilum, Thermoplasma volcanium and Thermogymnomonas acidicola, respectively. Based on the results of our genomic, phylogenetic, physiological and chemotaxonomic studies, we propose that strain M1T (=DSM 116605T=JCM 36570T) represents a new genus and species, Oxyplasma meridianum gen. nov., sp. nov., within the order Thermoplasmatales.

Enhanced photocatalysis by defect-engineered CeO2 with sulfite activation under visible light irradiation

Sulfite-based advanced oxidation processes (s-AOPs) have recently garnered significant attention due to their ability to generate highly oxidative sulfate radicals and eliminate contaminants from water. A state-of-the-art platform has been developed through the synergistic combination of s-AOP and photocatalysis under visible light as weak as ambient indoor daylight. This platform achieved an enhanced degradation efficiency for defect-engineered CeO2 nanocubes by using sodium sulfite instead of SO2, resulting in a synergy factor of up to 88%. The reaction pathways, intermediates, ion leaching and the possible influence of aqueous conditions during the methyl orange degradation have been investigated. The CeO2/Na2SO3/vis-light platform exhibits promising prospect as a system to enhance conventional s-AOP in wastewater treatment or disinfection. It demonstrates excellent performance in terms of pH sensitivity, anion influence, and resistance to leaching. This highlights its significant potential for practical applications and future process scale-up.

Groundwater quality in high-sulfur coal mining region of India: Spatial distribution, source control, and health risk assessment

The groundwater quality in the vicinity of the Makum coalfield, renowned for its high-sulfur coal deposits, was investigated. The oxidation of sulfur in the coal generates acid mine drainage (AMD), a global environmental challenge that contaminates natural resources. The region's high sulfur coal content intensifies AMD formation, necessitating a comprehensive assessment of its impact on human health and the environment. This study analyzes the water quality parameters such as pH, EC, TDS, Na+, Ca+2, Mg+2, K+, HCO3‐, SO4−2, F−, Cl -, and NO3− in groundwater, findings concerning low pH levels (5.8) and fluoride concentration (0.15 mg/L) compared to standards. Groundwater chemistry was analyzed to identify the sources controlling water composition through Gibbs diagrams, Piper diagrams, and saturation indices. The Gibbs diagram shows that rock weathering is the crucial factor controlling groundwater chemistry, while the Piper diagram indicates Ca-Cl as the Principal water type. Additionally, an in-depth analysis of groundwater chemistry reveals that carbonate dissolution primarily occurs due to minerals like calcite, dolomite, and gypsum, findings supported by saturation indices. The present study yielded an average water quality index of 40.19, indicating excellent to good water quality in 51 out of 52 samples analyzed. The average hazard index values for adults and children were 0.60 and 0.58, respectively, indicating that 49 of 52 samples pose negative non-carcinogenic risks associated with nitrate and fluoride contamination. The irrigation indices, graphical representations such as the Wilcox and Doneen classification, and the USSL diagram elucidate the suitability for irrigation purposes. Moreover, the Principal Component Analysis identified the sources of ions as originating from geogenic processes and mining activities. The study stresses environmental assessments, health risk management, and sustainable practices for groundwater in high-sulfur coal mining areas.

Study on Ship Exhaust Gas Denitrification Technology Based on Vapor-Phase Oxidation and Liquid-Phase Impingement Absorption

A system combining gas-phase oxidation and liquid-phase collision absorption for removing NO from marine diesel engine exhaust was proposed. This method was the first to utilize different physical states of the same mixed solution to achieve both pre-oxidation and impingement reduction absorption of exhaust gases. During the pre-oxidation stage, a mixture of (NH4)2S2O8 and urea solution was atomized into a spray using an ultrasonic nebulizer to increase the contact area between the oxidant and the exhaust gas, thereby efficiently pre-oxidizing the exhaust gas in the gas phase. In the liquid-phase absorption stage, the (NH4)2S2O8 and urea solution was used in an impingement absorption process, which not only enhanced gas–liquid mass transfer efficiency but also effectively inhibited the formation of nitrates. Experimental results showed that, without increasing the amount of absorbent used, the maximum NO removal efficiency of this method reached 97% (temperature, 343 K; (NH4)2S2O8 concentration, 0.1 mol/L; urea concentration, 1.5 mol/L; NO concentration, 1000 ppm; pH, 7; impinging stream velocity, 15 m/s), compared to 72% using the conventional liquid-phase oxidation absorption method. Additionally, this method required only the addition of a nebulizer and two opposing nozzles to the existing desulfurization tower to achieve simultaneous removal of sulfur and nitrogen oxides from the exhaust gas, with low retrofitting costs making it favorable for practical engineering applications.

Impacts of Climatic Changes and Air Pollution on Public health and Environment

Air pollution is an emerging highlight in developing countries in changing climate, it is considered one of the greatest concerns of public, individual, and environmental health. The rate of mortality and morbidity seems to increase due to air contamination. There are many types of air pollutants, some of the major air pollutants are particulate matter (PM), carbon monoxide (CO), nitrogen oxides (NOx), sulfur oxides (SOx), and lead (Pb). PM are minute suspended particles that can inhaled while breathing and cause cardiovascular and respiratory disorders, nervous system diseases, and cancer. High levels of CO inhalation cause poisoning in humans. Nitrogen oxides are latent greenhouse gases with high global warming potential and deplete the ozone layer. SOx causes intoxication when absorbed by the human body. When lead is absorbed by the human body by inhalation it may cause toxicity, chronic obstructive pulmonary disease, asthma, and lung cancer. Thereafter air pollution and changing climate lead to the spread of many infectious diseases. Hence, the way to manage this problem of air pollution is to make the public aware of impacts and management practices. The scientific and medical experts should conduct multidisciplinary research at the national and international level to sort out this problem in a sustainable way.

Environmental regulation and intermediate imports: Firm-product-level evidence

This study examines the effects of domestic environmental regulations on import activity. Using a panel of firm-product-level data and variations in regulatory stringency across products established by China’s Eleventh Five-Year Plan for Environmental Protection (covering 2006–2010), it reveals that tougher regulations on emission-intensive industries at home led to increases in downstream manufacturers’ imports of emission-intensive intermediate inputs. Specifically, a 1% increase in sulfur dioxide emission intensity resulted in a 0.026% increase in intermediate imports after the implementation of the regulation. A back-of-the-envelope calculation suggests that, although the regulation increased emissions in source countries, it reduced global emissions of sulfur oxides and carbon dioxide. This is because the increases in imports caused by the regulation mainly came from countries with lower emission intensity than China. The regulation did not disproportionately increase imports from or emissions in developing countries.

Enhanced Li bonds enable bidirectional sulfur catalysis by a molecular Co-N4 catalyst for lithium-sulfur batteries

Sulfur conversion catalysis is an effective strategy to tackle the inherent polysulfide shutting and fast capacity decay in lithium-sulfur batteries. Previous studies identified cobalt phthalocyanine as a unique molecular catalyst with Co-N4 active sites to promote sulfur reduction reactions. Herein, enhancing the Li bonds with the pyridinic N atoms on the phthalocyanine ligand is demonstrated to endow further catalytic activity in sulfur oxidation reactions. This is enabled by peripheral substitution with electron-donating methoxy groups that strengthens the electronegativity of the pyridinic N atoms. DFT calculations and metadynamics simulations identify the key role of Li bonds in reducing the energy barrier of Li2S dissociation. The highly lithiophilic methoxy groups also stabilize the dissociated Li cations in their solvation structure. The dissociated S anion can then be oxidized to higher-order polysulfides or radicals by electron donation to the Co-N4 center, which activates Li2S for subsequent oxidation. Meanwhile, the catalytic activity in sulfur reduction reactions is also improved by a more efficient electron transfer to adsorbed Li2S4, during which the strengthened Li bonds are beneficial in mediating the breakage of the bridging S-S bond. Significant performance improvements are achieved with the bidirectional catalyst under high areal sulfur loading and in Li-S pouch cells.

Effects of cable bacteria on vertical redox profile formation and phenanthrene biodegradation in intertidal sediment responded to tide

Periodic oxygen permeation is critical for pollutant removal within intertidal sediments. However, tidal effects on the vertical redox profile associated with cable bacterial activity is not well understood. In this study, we simulated and quantified the effects of tidal flooding, exposing, and their periodic alternation on vertical redox reactions and phenanthrene removal driven by cable bacteria in the riverbank sediment. Results show that electrogenic sulfur oxidation (e-SOx) mediated by cable bacteria during exposing process drove the vertical permeation of oxidation potential characterized by a decrease in Fe(II) and sulfide concentrations. The sulfate produced was observed in deep sediment (5–10 mm) and served as an electron acceptor for anaerobic oxidation, thereby triggering the functional succession of microbial community. About 78.2 % and 80.8 % of phenanthrene was degraded in deep sediment where cable bacteria grew well under exposing and tidal conditions. Anaerobic processes during tidal flood were also found to be important for the survival of cable bacteria. Higher cable bacteria abundance (up to 1.5 %) was observed under tidal conditions compared to that under continuous exposing conditions and flooding conditions. This might be attributed to lower oxidation stress and sulfide replenishment via sulfate reduction while flooding. Under tidal conditions, the cable bacteria interacted with sulfate reduction bacteria (e.g. Desulfobacca spp. and Desulfatiglans spp.) and maintained the dynamic balance of HS− and SO42− in sediment profiles. This HS−-SO42− cycle could serve as a “redox connector” that continuously delivers oxidation potential to deep sediments, resulting in the removal of organic pollutants. The findings provide preliminary evidence of the self-purification mechanisms within intertidal sediments and suggest a potential strategy for sediment remediation.

Experimental Investigation of Sulfur and Nitrogen Oxide Emissions and Corrosion Propensity During the Combustion of Coals and Biomass Fuels

ABSTRACT The increasing use of biomass in Indonesian coal-fired power plants, mainly through co-firing, presents challenges due to different fuel characteristics, which can affect gas emissions, ash deposition, and combustion efficiency. This study assesses flue gas emissions (SO2 and NOx) and corrosion tendencies of various biomass types and coal. The study begins with characteristic testing and ash analysis of coal and biomass samples, including proximate, ultimate, and calorific value analyses, to determine their suitability as fuels. Preliminary calculations predict flue gas emissions and ash deposit formation, followed by laboratory-scale combustion experiments using a DTF to assess flue gas and ash deposit characteristics. The results show that sulfur in biomass is converted to the gas phase up to 99%, while in coal, it is converted up to 95% at high temperatures. NOx levels are primarily affected by the nitrogen contents of the fuels; for instance, Coal-B at 0.88 wt% produces less NOx than solid recovered fuel (SRF) and refused derived fuel (RDF) with 1.73 wt% and 1.51 wt%, respectively, yet still generates higher emissions than the other three biomass types. In general, wood chips (WC), rise husk (RH), and palm kernel shell (PKS) emit 30–80% less flue gas compared to coal. However, ash deposition results indicate that PKS, SRF, and RDF exhibit corrosion tendencies due to the dominance of albite (NaAlSi3O8) in the mineral phase. Additionally, the high chlorine content in SRF (0.544 wt%) and RDF (0.224 wt%) leads to the formation of sticky ash deposits, which potentially impact heat transfer surfaces. These findings contribute to identifying suitable biomass types for both co-firing or dedicated combustion in coal-fired power plants.

Mechanism study on quantification of sulfurization effect on methane decomposition with CuO oxygen carrier

The sulfur-containing impurity in natural gas, coal, and organic solid wastes generally exerts significant impacts on the dynamic evolution of sulfur oxides emission in atmosphere, and results in the degraded reaction performance of chemical looping process. Methane is the main component of natural gas and a typical pyrolysis and gasification product of solid waste, so it is of great significance to quantify the toxicological effects on the conversion of methane. this work realizes the accurate prediction of methane heterogeneous conversion in a multiscale kinetic model, and innovatively establishes a framework for quantifying the toxicological effect on the oxygen carrier particles. The kinetic parameters of methane oxidation over fresh and sulfurized oxygen carriers are calculated using density functional theory, and the sensitivity analysis of rate constant is conducted to forecast the priority of different reactions. Results indicate that the effect of residual sulfur in oxygen carrier is complex and not monotonically inhibited, and the sulfurization significantly limits the methane oxidation reactivity by reducing the reaction rate of the rate-limited dissociation step under the high-temperature condition. The multi-scale kinetic simulations reveal that the maximum instantaneous rate of sulfurized oxygen carrier is decreased by 7.45 %, which is deemed as the attenuation factor of 0.9255 derived from the toxicological effects of sulfurization.

Calcined pyrite accelerates sulfur metabolic and electron transfer in driving targeted microbial fuel cell denitrification

The sulfur powder as electron donor in driving dual-chamber microbial fuel cell denitrification (S) process has the advantages in economy and pollution-free to treat nitrate-contained groundwater. However, the low efficiency of electron utilization in sulfur oxidation (ACE) is the bottleneck to this method. In this study, the addition of calcined pyrite to the S system (SCP) accelerated electron generation and intra/extracellular transfer efficiency, thereby improving ACE and denitrification performance. The highest nitrate removal rate reached to 3.55 ± 0.01 mg N/L/h in SCP system, and the ACE was 103 % higher than that in S system. More importantly, calcined pyrite enhanced the enrichment of functional bacteria (Burkholderiales, Thiomonas and Sulfurovum) and functional genes which related to sulfur metabolism and electron transfer. This study was more effective in removing nitrate from groundwater without compromising the water quality.

SBA-15 Type Mesoporous Silica Modified with Vanadium as a Catalyst for Oxidative and Extractive Oxidative Desulfurization Processes.

One of the current challenges is the reduction of sulfur emitted into the atmosphere, usually in the form of sulfur oxides generated by fossil fuel combustion. To achieve this goal, the sulfur content should be reduced in fuel. In this context, vanadium-containing materials based on SBA-15 mesoporous silica supports and two different sources of vanadium were prepared, characterized, and applied as catalysts for oxidative desulfurization (CODS) and extractive oxidative desulfurization processes (ECODSs). The novelty of this work was the comparative study of vanadium-containing materials in two desulfurization systems. The properties of the catalysts, the concentration and state of vanadium species, and their role in the catalytic process were examined by low-temperature nitrogen physisorption, XRD, UV-Vis, XPS, and chemisorption of pyridine combined with FTIR spectroscopy. The catalytic performance of the material prepared using ammonium metavanadate was superior to that of the catalyst obtained using vanadium(IV) oxide sulfate, which was explained by a higher concentration of vanadium species on the surface of the support and their lower oxidation state in the former. Both types of catalysts showed high activity and stability in the ECODS process.

Transition to the New Green Maritime Era—Developing Hybrid Ecological Fuels Using Methanol and Biodiesel—An Experimental Procedure

The conventional utilization of fossil fuels precipitates uncontrolled carbon dioxide and sulfur oxides emissions, thereby engendering pronounced atmospheric pollution and global health ramifications. Within the maritime domain, concerted global initiatives aspire to mitigate emissions by 2050, centering on the adaptation of engines, alteration of fuel compositions, and amelioration of exhaust gas treatment protocols. This investigation pioneers experimentation with marine gas oil augmented by methanol, a practice conventionally encumbered by prohibitively expensive additives. Successful amalgamation of methanol, animal-derived biodiesel, and marine gas oil (MGO) is empirically demonstrated under meticulously controlled thermal conditions, creating a homogeneous blend with virtually zero sulfur content and reduced carbon content, featuring characteristics akin to conventional marine gas oil but with no use of expensive emulsifiers. This new blend is suitable for employment in maritime engines utilizing Delaval technology, yet with significantly lower energy requirements compared to those necessitated using conventional very low sulfur fuel oil (VLSFO) with a maximum sulfur content of 0.5% w/w.

Effect of Organic, Nano, and Inorganic Zinc Sources on Growth Performance, Antioxidant Function, and Intestinal Health of Young Broilers.

The study aimed to determine the effects of different zinc sources on growth performance, antioxidant function, and intestinal health of broilers. In total, 240 Ross 308 male broilers with similar weight were randomly assigned to 4 treatments, including zinc sulfate, methionine zinc (Zn-Met), glycine zinc (Zn-Gly), and nano-zinc oxide (ZnO-NPs), with 80mg zinc/kg diet supplementation. The experiment lasted for 21days. Results showed dietary supplemental Zn-Gly and Zn-Met increased average daily gain during 1-14days (P = 0.011), and Zn-Gly, Zn-Met, and ZnO-NP supplementation decreased the ratio of feed to gain during 1-21days (P = 0.003) compared to zinc sulfate. ZnO-NPs supplementation tended to increase total SOD activity (P = 0.068) and had higher serum IgA content and lower MDA level than the other three groups (P < 0.05). Compared with zinc sulfate, Zn-Met and ZnO-NP supplementation decreased TNF-α mRNA expression (P = 0.048). However, serum biochemical indices, intestinal morphology, and mRNA expressions of tight junction proteins were not affected by different zinc sources (P > 0.05). A differential trend was observed in the beta diversity of bacterial communities among four groups (P = 0.082). The LEfSe analysis showed that bacterial genera Blautia, Ruminococcaceae, Clostridia, Anaerostipes, Eubacterium_ventriosum, Merdibacter, and Oscillospira were enriched in the ZnSO4 group, and the genera Eubacterium_hallii and Anaerotruncus were enriched in the Zn-Gly group. The genera UCG-009 and UCG010 were enriched in ZnO-NPs and Zn-Met groups, respectively. It should be stated dietary supplemental Zn-Met improved growth performance, ZnO-NPs promoted IgA production and reduced occurrences of oxidative stress and inflammation, and different zinc sources enriched different jejunal bacteria genera.

Developing and Testing Standards to Assess Atmospheric Corrosion of Silver Witness Coupons

Silver witness coupons are used to assess the corrosivity and chemistry of an ambient environment. The formation of silver corrosion products such as silver chloride is highly dependent on local conditions. However, the mechanisms that are responsible for these corrosion products are not well-understood, and there is a lack of standards used to compare and assess the quality of observations.The goal of this study is to synthesize silver corrosion film standards with known thickness and morphology. Compounds of interest include silver chloride, silver oxide, silver sulfide, silver sulfite, and silver sulfate. These compounds were generated electrochemically by oxidizing the silver in the presence of the anion of interest (chloride, sulfite, or sulfate), chemically by submerging the silver in a solution containing the anion, and chemically by dipping the silver in molten silver salts. The surface chemistry of these films was then analyzed using galvanostatic reduction, x-ray diffraction, x-ray photon spectroscopy, Raman spectroscopy, and energy dispersion spectroscopy. The films generated from each method were compared against each other to determine the optimal film thickness and morphology. In the future, these results will be compared against the surface chemistry of silver films formed by testing in laboratory chambers or by exposure in field environments. Figure 1

Chalcopyrite bioleaching efficacy by extremely thermoacidophilic archaea leverages balanced iron and sulfur biooxidation

Factors that contribute to optimal chalcopyrite bioleaching by extremely thermoacidophilic archaea were examined for ten species belonging to the order Sulfolobales from the genera Acidianus (A. brierleyi), Metallosphaera (M. hakonensis, M. sedula, M. prunae), Sulfuracidifex (S. metallicus, S. tepriarius), Sulfolobus (S. acidocaldarius), Saccharlobus (S. solfataricus) and Sulfurisphaera (S. ohwakuensis, S. tokodaii). Only A. brierleyi, M. sedula, S. metallicus, S. tepriarius, S. ohwakuensis, and S. tokodai exhibited significant amounts of bioleaching and were investigated further. At 70–75 °C, Chalcopyrite loadings of 10 g/l were leached for 21 days during which pH, redox potential, planktonic cell density, iron concentrations and sulfate levels were monitored, in addition to copper mobilization. S. ohwakuensis proved to be the most prolific bioleacher. This was attributed to balanced iron and sulfur oxidation, thereby reducing by-product (e.g., jarosites) formation and minimizing surface passivation. Comparative genomics suggest markers for bioleaching potential, but the results here point to the need for experimental verification.

Assessment of zinc sources and levels for urea coating to achieve higher productivity and soil fertility in spring maize (Zea mays)

An experiment was conducted during 2021 and 2022 at the research farm of ICAR-Indian Institute of Maize Research, Ludhiana, Punjab to study the efficacy of zinc oxide and zinc sulphate for urea coating to achieve higher productivity in maize (Zea mays L.). Experiment was laid out in a randomized block design (RBD) comprised of 11 treatments, viz. no Zn; 0.05% of Zn through ZnO; 0.12% of Zn through ZnO; 0.24% of Zn through ZnO; 0.47% of Zn through ZnO; 0.95% of Zn through ZnO; 0.26% of Zn through ZnSO4; 0.52% of Zn through ZnSO4; 1.03% of Zn through ZnSO4; 2.07% of Zn through ZnSO4; and 4.15% of Zn through ZnSO4, replicated thrice. Results indicated that grains/cob and cob weight/plant recorded higher with 1.03%, 2.07% and 4.15% of Zn through ZnSO4 compared to no Zn. Zn at 2.07% (5.68 and 6.36) and 4.15% (5.71 and 6.37) through ZnSO4 recorded higher grain yield followed by 0.95% of Zn (5.50 and 6.23) through ZnO and 1.03% (5.42 and 6.25) of Zn through ZnSO4 in 2021 and 2022. A higher Zn content in grain was registered with 4.15% (27.70 and 27.87 mg/kg) and 2.07% (26.33 and 27.67 mg/kg) of Zn through ZnSO4. Overall, Zn at 2.07% through ZnSO4 was found suitable for urea coating to enhance productivity, soil enzymatic activities and residual soil fertility in spring maize.