Granulation of finely crystalline ammonium sulphate using calcium oxide and sulphuric acid

Two types of finely crystalline ammonium sulphate (particle size distributions: white type 7% 2–3 mm, 45% 1–2 mm, 48% <1 mm; blue type 1% 2–3 mm, 8% 1–2 mm, 91% <1 mm) were granulated by adding calcium oxide and concentrated sulphuric acid using a rotating drum in the laboratory and pilot plant. The granules had satisfactory physical and chemical properties.The granules made in the pilot plant with 25 kg ammonium sulphate, 0.5 kg CaO, 1.26 litres of water and 0.9 to 1.125 litres of 98.5% H₂SO₄ had 80 to 97% of the granules within the size range of 1–3 mm, abrasion resistance of 0.4 to 0.8% <1 mm, crushing strength of 1.4 to 2.3 kg, critical relative humidity of 65–70%, pH 1.8 to 1.9 and N, S and Ca contents of 19, 24 and 1%. The quality of the granules when stored for 6 months alone or blended together with common fertilizers did not change.A glass house trial using barley demonstrated that the agronomic values of 4 prototype ammonium sulphate granules produced in the laboratory were similar to 3 standard granular ammonium sulphate fertilizers.The process of granulation which could easily be adopted in superphosphate manufacturing plants is recommended for plant scale testing.Provisional New Zealand Patent (No 236,025) applied for.     

Fate of Fertilizer15N applied as urea and ammonium sulphate in opium poppy (Papaver somniferum L.) grown under greenhouse conditions

Laboratory incubation and greenhouse experiments were conducted to investigate the comparative effectiveness of urea and ammonium sulphate in opium poppy (Papaver somniferum L.) using¹⁵N dilution techniques. Fertilizer treatments were control (no N), 600 mg N pot^–1 and 1200 mg N pot^–1 (12 kg oven dry soil) applied as aqueous solution of urea or ammonium sulphate. Fertilizer rates, under laboratory incubation study were similar to that under greenhouse conditions. A fertilizer¹⁵N balance sheet reveals that N recovery by plants was 28–39% with urea and 35–45% with ammonium sulphate. Total recovery of¹⁵N in soil-plant system was 77–82% in urea. The corresponding estimates for ammonium sulphate were 89–91%. Consequently the unaccounted fertilizer N was higher under urea (18–23%) as compared to that in ammonium sulphate (9–11%). The soil pH increased from 8.2 to 9.4 with urea whereas in ammonium sulphate treated soil pH decreased to 7.3 during 30 days after fertilizer application. The rate of NH₃ volatilization, measured under laboratory conditions, was higher with urea as compared to the same level of ammonium sulphate. The changes in pH of soil followed the identical trend both under laboratory and greenhouse conditions.     

Use of large granular urea (LGU) to improve efficiency of broadcast urea in wetland rice cultivation

Laboratory and greenhouse experiments were conducted to determine whether the efficiency of broadcast urea in wetland rice cultivation can be improved by using large granules which penetrate the puddled soil. In laboratory experiments the penetration increased with increasing granule size. Penetration was improved by having only a waterfilm on the soil and by the granules entering the soil with speed.In pot experiments with rice, N concentrations in the floodwater were lower with large granular urea (LGU, 6 to 8 mm diameter) dropped from a height of 2 m or shot with force into the puddled soil than with either prilled urea (PU) or LGU placed on top of the soil (+0cm). N concentrations in the floodwater were reduced even further by placement of LGU at 1 and 4 cm depths (–1 and –4cm, respectively). At all rates of N, the N uptake by grain plus straw increased with decreasing N concentrations in the floodwater. The apparent recovery of N in grain plus straw increased in an experiment on sandy soil from 61 to 85% in the order PU +0cm, LGU +0cm, LGU dropped, LGU –1cm, LGU shot and LGU –4cm. In an experiment on clay soil apparent recovery increased from 47 to 90% in the order PU +0cm, LGU +0cm, LGU dropped, LGU –0cm, LGU shot, LGU –1cm and LGU –4cm. LGU placed at –1 and –4cm resulted in significantly greater N uptake by grain plus straw than the other treatments.The experiments showed that the efficiency of broadcast urea is improved by using large urea granules, at least when conditions are favourable for penetration into the puddled soil.     

Effect of urea granule size on ammonia volatilization from surface-applied urea

Urea powder and granules of varying size (1 to 8 mm diameter) were surface applied to a ryegrass/white clover pasture. Evolution of NH₃ was measured using a continuous air flow enclosure method. At 30 kg N ha^–1, the percentage of urea-N lost as NH₃ from powder or granules of 1–2, 3–4, 5.6 and 8 mm diameter was 18, 17, 20, 22 and 32 respectively. As the particle size increased, the rate of urea hydrolysis decreased and delayed the time at which the maximum rate of volatilization occurred. Mineral-N and soil surface pH measurements confirmed that during the period of volatilization, urea moved less than 30 mm from the application point.For the powder and 3–4 mm granule treatments, when the application rate was increased from 30 to 300 kg N ha^–1, the percentage of urea-N volatilized increased, but at any particular rate there was no significant difference in percentage loss between the powder and 3–4 mm granules.     

Acidic and basic binders for magnesite based aggregate in plaster of tundish

Binders are generally inorganic, organic or organomineral and have an important influence on the performance and corrosion resistance of slag line and deskulling. Since silicate and phosphate binders have some side effects, in this work sulphate binders such as sulphamic acid, H₂NSO₃H; aluminum sulphate, Al₂(SO₄)₃; ammonium sulphate, (NH₄)₂SO₄; magnesium sulphate, MgSO₄; calcium sulphate, CaSO₄; sodium sulphate, Na₂SO₄; and potassium sulphate, K₂SO₄, are investigated. Cold crushing strength at different heat treatments of room temperature, 110 °C, 1100 °C, 1400 °C is measured. Apparent porosity of samples without pulp and bulk density together with pH of the binder solution is evaluated and XRD and SEM studies are performed. Among these sulphate binders MgSO₄ was found to be the best. It is acidic in nature and develops strong bonds to the basic aggregate, MgO, at low temperatures. At high temperatures it dissociates from MgO(s) and SO₃(g) and the remained portion of MgO is the same as host oxide, with no corrosion and easy deskulling. Basic binders such as calcium sulphate, sodium sulphate and potassium sulphate could not strongly bond the MgO aggregates.     

Granulation of particulate oxide materials

Conclusions The improved technology for granulating particulate oxide materials using the grains of inoculator seeds makes it possible to reduce the period of granulation and to increase the yield of the final granules. The waste products obtained during production of flaky (platelike) corundum can be used as the inoculator grains. In order to obtain granules having an ellipticity not exceeding 0.5–0.7 mm, the optimum size of the inoculator grains is 1–2 mm.The inoculator grains obtained from the low-fired (undersintered) material has advantages over the densely sintered materials from the standpoint of improved internal structure of the granules. We established the optimum quantity of the inoculator grains for obtaining granules measuring (20±3) mm in diameter using a granulator having a diameter of 1000 mm with minimum irretrievable waste products during the initial period of granulation.We studied the growth kinetics during seedless granulation and during granulation with an inoculator. It was shown that densification of the granules occurs during granulation. We determined the main physical and mechanical properties of the granules obtained by granulating on the inoculator grains and by seedless granulation and established the optimum composition of the binding solution (binder) incorporating a phosphate-containing component as strengthening agent.Translated from Ogneupory, No. 6, pp. 10–13, June, 1989     

Effect of rates and sources of nitrogen application on yield and nutrient uptake of Citronella Java (Cymbopogon winterianus Jowitt)

Two field experiments were conducted for two crop cycles each of two years (1985–87 and 1986–88) on an entisols to study the effect of rate and sources of N application on yield and nutrient uptake of Citronella Java (Cymbopogon winterianus Jowitt). Fresh herbage and essential oil yields were significantly influenced by application of N up to 200 kg ha^–1 yr^–1, while tissue N concentration and N uptake increased only to 150 kg N ha^–1. The oil yields with Neem cake coated urea (urea granules coated with Neem cake) and urea super granules were 22 and 9% higher over that with prilled urea and urea supergranules were significantly increased up to 200 kg N ha^–1 while with Neem cake coated urea, response was observed only to 150 kg N ha^–1! Estimated recovery of N during two years from Neem cake coated urea, urea supergranules and prilled urea were 38, 31 and 21%, respectively.     

Fate of nitrogen (15N) from oxamide and urea applied to turf grass: A lysimeter study

Slow release N fertilizers are receiving increasing attention for use on turf grass, but their fate in the plant-soil system is still poorly understood. We aimed to quantify the uptake and recovery of N by a mixture of grasses when applied as either urea or oxamide in different diameter granules using a tracer technique (¹⁵N). The effects of the N source on soil biomass, root density and amount of readily available organic C in soil were also evaluated.In a first experiment oxamide in 4–5 mm diameter granules was compared with urea. The initial N absorption, 40 days after fertilization (d.a.f.), was higher for urea (23.5%) than for oxamide (12.1%), but after 64 days absorption efficiencies were about the same (11%) for both fertilizers. Fertilizer-derived N lost by leaching was much greater from the urea-fertilized soil (1.57 g), compared with losses from oxamide-fertilized soil (0.05 g). The total residual fertilizer N remaining in the system at the end of the experiment was 26.7% of applied urea N and 39.6% of applied oxamide N. Cumulated absorption efficiencies, calculated after dismantling the lysimeters, were 43.1% for urea and 54.8% for oxamide (roots included). A priming effect caused by a larger uptake of soil N because of the better root development was found in the oxamide-treated lysimeter. Fertilization with oxamide also caused an increase in the amount of soil microbial biomass.In a second experiment, the efficiencies and fertilizer N uptake rates from oxamide applied at two different granule sizes (1–2 mm and 5–10 mm) were evaluated. The amount of soil N taken up by the grass was linearly related to root density (r = 0.92).     

Obtaining granular NPK fertilizers from single superphosphate and urea

A laboratory study was conducted to elaborate methods for obtaining granular NPK fertilizers from mixtures of single superphosphate (SSP) with urea and potassium salts. Samples of products of various grades containing 32–39% fertilizer nutrients and some micronutrients (B, Cu, Co, Mo, Mn) were obtained and their characteristics determined. Instead of cured SSP the usage of a fresh den product was recommended to reduce environmental pollution. The best results were obtained by drying den superphosphate and neutralizing it with limestone before mixing it with other components. Granulation of mixtures should be carried out by the thermic method at 80–95°C, on account of the liquid phase from melting urea. The hardness of the granules obtained by this method, when stored in a dry room, remained satisfactory for 3 months.This paper is dedicated to the memory of Edgar Arumeel (1911–1993)     

Movement and transformations of fertigated nitrogen below trickle emitters and their effects on pH in the wetted soil volume

The movement and transformations of ammonium-, urea- and nitrate-N in the wetted volume of soil below the trickle emitter was studied in a field experiment following the fertigation of N as ammonium sulphate, urea and calcium nitrate. Effects on soil pH in the wetted volume were also investigated.During a fertigation cycle (emitter rate 2lh^–1) applied ammonium was concentrated in the surface 10 cm of soil immediately below the emitter and little lateral movement occurred. In contrast, because of their greater mobility in the soil, fertigated urea and nitrate were more evenly distributed down the soil profile below the emitter and had moved laterally in the profile to 15 cm radius from the emitter. The conversion of applied N to nitrate-N was more rapid when urea rather than ammonium-N was applied suggesting that the accumulation of large amounts of ammonium below the emitter in the ammonium sulphate treatment probably retarded nitrification.Following their conversion to nitrate-N, both fertigated ammonium sulphate and urea caused acidification in the wetted soil volume. Acidification was confined to the surface 20 cm of soil in the ammonium sulphate treatment, however because of its greater mobility, fertigation with urea (2lh^–1) resulted in acidification occurring down to a depth of 40 cm. Such subsoil acidity is likely to be very difficult to ameliorate. Increasing the trickle discharge rate from 2lh^–1 to 4lh^–1 reduced the downward movement of urea and encouraged its lateral spread in the surface soil. As a consequence, acidification was confined to the surface (0–20 cm) soil.     

Ammonia volatilization from urea and ammoniacal fertilizers surface applied to winter wheat and grassland

Ammonia volatilization from urea, diammonium phosphate, ammonium sulphate and calcium ammonium nitrate surface applied to winter wheat and grassland was determined with windtunnels. The fertilizers were applied at a rate of 8–12 g N m^–2 to plots on a non-calcareous sandy loam. Five experiments were carried out during March to June 1992, each experiment including 2 to 4 treatments with two or three replications. The daily ammonia loss rate was measured during 15 to 20 days. Cumulated daily loss of ammonia from urea followed a sigmoidal expression, while the cumulated ammonia loss from diammonium phosphate showed a logarithmic relationship with time from application. For ammonium sulphate and calcium ammonium nitrate no significant loss could be determined, because daily loss of ammonia were at the detection limit of the wind tunnels. Mean cumulated ammonia loss from plots receiving urea, diammonium phosphate, ammonium sulphate and calcium ammonium nitrate were 25%, 14%, <5% and <2%, respectively, during a 15–20 day measuring period.     

The leaching and chemical transformations of surface-applied urea under flood irrigation

The depth of leaching and the rate of chemical transformation of surface-applied granular urea was studied in the field and in intact soil cores in the laboratory following the flood irrigation of a young barley crop. In the field, preferential flow of urea occurred to 300–400 mm depth with the application of 50 mm of irrigation, but the urea concentration remained greatest in the surface (0–50 mm) layer. In contrast, leaching of urea was dominated by miscible displacement under 100 mm of irrigation in the field. Little urea remained in the surface layer after irrigation and maximum urea concentration occurred at 200–400 mm depth. There was no apparent significant redistribution of urea or its hydrolysis products through the profile after the initial sampling. Urea leaching patterns in intact soil cores were different to those in the field and were largely unaffected by irrigation volume. Preferential water flow occurred through the soil cores, although most of the applied urea was by-passed and remained in the surface layer. Transformation rates of urea were similar in the field and in soil cores. Urea was transformed to ammonium within 48 h, with almost complete conversion of ammonium to nitrate within 192 h of application.     

Potassium availability with application of sewage sludge,and sludge and manure composts in field experiments

An experiment was conducted to determine the plant availability of K in organic wastes. Four materials: digested sewage sludge (DSS), digested irradiated sludge (DISS), digested, irradiated and composed sludge (DICSS), and composted livestock manure (CLM) were applied to farmland for two years at rates of 10, 20, 30, and 40 mg-solids ha^–1 yr^–1. Potassium fertilizer (KCl) was added to the control treatment (CT), to which no waste was applied, and to the low-rate waste applications, to meet crop K requirement. Equal yields within different treatments were obtained for the test crops lettuce and snap beans through application of available N at the levels balanced for crop economical production. Potassium from the wastes was evaluated based on the assumption that Crop K uptake/Available K applied was equal between the CT and waste treatments. The results indicated that, in general, K applied with wastes (waste K + fertilizer K) was equally available (101±7%) to fertilizer K (KCl), except for low rate application of DISS (10 Mg ha^–1), where the availability of K was low (89±1%).     

The effect of fertiliser type and application rate on denitrification losses from cut grassland in Northern Ireland

Denitrification losses were measured using the acetylene inhibition technique adapted for a coring procedure. Two soils under a cut ryegrass sward were used. One soil was a freely-drained clay loam receiving under 900 mm rainfall annually, the other soil being a poorly-drained silty clay receiving over 1100 mm rainfall annually. Swards at each site received up to 300 kg N ha^–1 yr^–1 of calcium ammonium nitrate (CAN), urea or a new fertiliser mixture GRANUMS (30% ammonium nitrate, 30% urea, 10% ammonium sulphate, 30% dolomite). For both soils the rate of denitrification exceeded 0.1 kg N ha^–1 day^–1 only when the air-filled porosity of the soil was < 30% v/v and soil nitrate was > 2 mg N kg^–1 in the top 10cm of the profile and when soil temperature at 10 cm was > 4°C. When the soils dried such that their air-filled porosity was > 30% v/v, denitrification rates decreased to < 0.08 kg N ha^–1 day^–1. Highest rates (up to 3.7 kg N ha^–1 day^–1) were observed on the clay soil following application of 94 kg N ha^–1 CAN to soil near field capacity in early summer 1986. Losses from CAN were approximately 3 times those from urea for a given application. Denitrification losses from the GRANUMS treatment were, overall, intermediate between those from CAN and urea but the daily losses more closely resembled those from the CAN treatment. The impeded drainage on the clay soil, where soil moisture contents remained close to field capacity throughout the year, showed denitrification losses roughly 3 times those observed on the more freely drained clay-loam for any given treatment. Over a 12-month period, N losses arising from denitrification were 29.0 and 10.0 kg N ha^–1 for plots receiving 300 kg N ha^–1 CAN and urea, respectively, on the well drained clay-loam and 79.0 and 31.1 kg N ha^–1 respectively, for identical plots on the poorly drained clay soil. Annual denitrification losses from control plots were < 1 kg N ha^–1 on both soils.     

Nitrogen transformations near urea in soil: Effects of nitrification inhibition,nitrifier activity and liming

A laboratory incubation experiment was conducted to gain a better understanding of N transformations which occur near large urea granules in soil and the effects of dicyandiamide (DCD), nitrifier activity and liming. Soil cores containing a layer of urea were used to provide a one-dimensional approach and to facilitate sampling. A uniform layer of 2 g urea or urea + DCD was placed in the centre of a 20 cm-long soil core within PVC tubing. DCD was mixed with urea powder at 50 mg kg^–1 urea and enrichment of soil with nitrifiers was accomplished by preincubating Conestogo silt loam with 50 mg NH ₄ ⁺ -N kg^–1 soil. Brookston clay (pH 5.7) was limited with CaCO₃ to increase the pH to 7.3. The cores were incubated at 15°C and, after periods of 10, 20, 35 and 45 days, were separated into 1-cm sections. The distribution of N species was similar on each side of the urea layer at each sampling. The pH and NH ₄ ⁺ (NH₃) concentration were very high near the urea layer but decreased sharply with distance from it. DCD did not influence urea hydrolysis significantly. Liming of Brookston clay increased urea hydrolysis. The rate of urea hydrolysis was greater in Conestogo silt loam than limed Brookston clay. Nitrite accumulate was relatively small with all the treatments and occurred near the urea layer (0–4 cm) where pH and NH ₄ ⁺ (NH₃) concentration were high. The nitrification occurred in the zone where NH ₄ ⁺ (NH₃) concentration was below 1000µgN g^–1 and soil pH was below 8.0 and 8.7 in Brookston and Conestogo soils, respectively. DCD reduced the nitrifier activity (NA) in soil thereby markedly inhibiting nitrification of NH ₄ ⁺ . Nitrification was increased significantly with liming of the Brookston soil or nitrifier enrichment of the Conestogo soil. There was a significant increase in NA during the nitrification of urea-N. The (NO ₂ ^– + NO ₃ ^– )-N concentration peaks coincided with the NA peaks in the soil cores.A practical implication of this work is that large urea granules will not necessarily result in NO ₂ ^– phytotoxicity when applied near plants. A placement depth of about 5 cm below the soil surface may preclude NH₃ loss from large urea granules. DCD is a potential nitrification inhibitor for use with large urea granules or small urea granules placed in nests.     

粘结剂对核桃壳基炭分子筛空分性能的影响

考察了三种粘结剂对产品炭分子筛空分性能的影响，表明在煤焦油粘结剂中添加少量造纸浆废液或聚乙烯醇有助于改善炭分子筛空分性能，并能减少其颗粒表面含尘量。     

Efficiency of some modified urea fertilisers for wetland rice grown on a permeable soil

Split broadcast applications of prilled urea, deep point-placed urea supergranules (USG), and broadcast sulfur-coated urea (SCU) were compared as nitrogen sources for wetland rice (Oryza sativa L.) in two field experiments on a sandy soil (Typic Ustipsamment) with a high percolation rate (approx. 110 mm/day) in the Punjab, India. The USG was consistently less effective than the split urea and averaged 1 ton ha^–1 less rice yield at the highest nitrogen rate (116 kg N ha^–1). SCU produced the highest grain yields in both experiments; it averaged 1.7 ton ha^–1 more than did the split urea at the highest N rate.The fertilisers were then compared in field microplots; percolation was permitted or prevented so that the cause of the poor performance of USG could be elucidated. USG gave higher grain yield and N uptake in microplots that were not leached than in those that were leached. In leached microplots, the grain yields were higher from prilled urea than from USG treatments provided the placement pattern of the USG matched that of the field plots. Yields were not higher from treatments in which the USG were more closely spaced. In microplots in which leaching was prevented, the broadcast prilled urea was less effective than the deep-placed USG, which gave yields approximately 60% greater than those from split urea and the same as those from SCU. Broadcast prilled urea in undrained microplots caused high levels of ammonium (40 ppm) to develop in the floodwater where high pH (8.9) and high alkalinity (4.9 meq l^–1) may have led to extensive ammonia volatilisation. The use of USG and SCU in undrained microplots reduced floodwater ammonium levels to less than 3 ppm.Urea and ammonium leaching losses measured in fallow soil columns in the laboratory were much greater from USG than from prilled urea. Leaching losses from SCU were negligible. The data suggest that SCU is the preferred N source for rice soils having a high percolation rate and that USG is a poor alternative to split applications of prilled urea.     

Recovery of lignosulphonate from a calcium bisulphite pulp mill effluent by ultrafiltration

An investigation has been carried out on the recovery of lignosulphonate from the spent liquor from a calcium bisulphite wood pulping mill. The mill uses mainly Eucalyptus wood and the spent liquor contains 16% total dissolved solids rich in lignosulphonate, sugars and acetic acid.The lignosulphonates and saccharides are both potentially useful components and in any water reclamation scheme, recovery of these constituents could be an important aspect.This paper is primarily concerned with the use of ultrafiltration for the recovery of lignosulphonate. Exploratory tests were carried out on a laboratory flat sheet rig.A range of ultrafiltration membranes with different molecular mass limits was used. The lignosulphonate liquor however, tends to throw down a dynamic membrane which effectively alters the ‘normal’ separation characteristics of the membrane chosen.In all cases, there was a dramatic drop in flux due to the components of the liquor. This was followed by a slower decline related to concentration. However, tests showed that lignosulphonates can be recovered from spent liquor by ultrafiltration and the ratio of sugars and acetic acid to total solids in the starting feed can be increased significantly in the permeates. Concentrations of over 300 gl⁻¹ total dissolved solids were achieved at reasonable flux rates.The precipitation of ellagic acid and calcium sulphite during the course of filtration must be allowed for in operating procedures.Conventional membranes should be available in suitable module forms such as plate and frame or tubular forms. These modules are more suitable to an effluent which is likely to deposit solids during separation.     

Effect of nitrification inhibitors on herb and essential oil yield of Japanese mint on sandy soil

Pyrethrum (Chrysanthemum cinerariefolium) flowers have been observed to have insecticidal properties and could be used as an indigenous nitrification inhibitor for increasing N-use efficiency. A field experiment was conducted at the Central Institute of Medicinal and Aromatic Plants, Lucknow, India during 1988 and 1989 to evaluate the relative performance of pyrethrum flower waste and Dicyandiamide (DCD) as nitrification inhibitors applied with prilled urea (PU) to Japanese mint (Mentha arvensis L.). The results revealed that application of the nitrification inhibitors with prilled urea significantly increased the herb and essential oil yield of the crop compared to that of prilled urea alone. Addition of Dicyandiamide and pyrethrum flower waste gave 30 and 23% more herb yield than prilled urea alone, the corresponding increase in oil yield being 27 and 22%, respectively. Application of nitrogen at 200 kg ha^–1 in dicayndiamide or pyrethrum flower waste treated soil significantly enhanced the herb and essential oil yields and N-uptake by the crop to more than that for 300 kg N ha^–1 with prilled urea. Both the materials improved the N use efficiency by one and half time as compared to that with PU at 100 kg N ha^–1. The results indicate pyrethrum flower dust can be effectively used as a potential nitrification inhibitor.     

Calcium sulfoaluminate cement blended with OPC: A potential binder to encapsulate low-level radioactive slurries of complex chemistry

Investigations were carried out in order to solidify in cement a low-level radioactive waste of complex chemistry obtained by mixing two process streams, a slurry produced by ultra-filtration and an evaporator concentrate with a salinity of 600 gxL^− 1. Direct cementation with Portland cement (OPC) was not possible due to a very long setting time of cement resulting from borates and phosphates contained in the waste. According to a classical approach, this difficulty could be solved by pre-treating the waste to reduce adverse cement–waste interactions. A two-stage process was defined, including precipitation of phosphates and sulfates at 60 °C by adding calcium and barium hydroxide to the waste stream, and encapsulation with a blend of OPC and calcium aluminate cement (CAC) to convert borates into calcium quadriboroaluminate. The material obtained with a 30% waste loading complied with specifications. However, the pre-treatment step made the process complex and costly. A new alternative was then developed: the direct encapsulation of the waste with a blend of OPC and calcium sulfoaluminate cement (CS̄̄A) at room temperature. Setting inhibition was suppressed, which probably resulted from the fact that, when hydrating, CS̄̄A cement formed significant amounts of ettringite and calcium monosulfoaluminate hydrate which incorporated borates into their structure. As a consequence, the waste loading could be increased to 56% while keeping acceptable properties at the laboratory scale.