3 PROJECT OBJECTIVES 1. Toneutralize spent acid using different materials2. To quantifythe neutralization process3. To performheat treatment4. Tocharacterize the iron oxide red pigment derived 2.1 RECYCLING OF SLUDGE GENERATED FROM STAINLESS STEELPICKLING PROCESSThis article by M. E.
Z. J.-x. C.
Y.-r. LI Xiao-ming,explains about recycling of sludge that is formed during pickling process.Recycling of stainless steel pickling sludge is very significant from botheconomic and environmental sides due to the presence of valuable elements suchas Ni and Cr.
There are several processes that are believed to be effectivemethods to dispose these wastes, but it comes along with both pros and cons,such as solidification/stabilization processes and pyro metallurgical andhydrometallurgical processes. By using methods such as research activities inthe field of sludge treatment and drying pickling sludge at differenttemperatures have resulted in pickling sludge has more metal oxides and a smallcontent of calcium sulphate compared to that of natural fluorspar. Sinteredsludge was charged into an electric furnace to check its ability. The recoveryof metal elements was calculated from the mass balance for each element and theresults shows that recovery of Ni, Cr and Fe is above 80%. In conclusion, therecycling of pickling sludge within ironmaking and steelmaking plant is themost promising way to treat these wastes. The recommended process would be:Pickling sludge ? (drying + sintering) ? BF/EAF.
By this method, the metalelements can be recovered efficiently, and the calcium oxides and fluorite canbe used properly 7. 2.2 RECOVERY OFZINC FROM INDUSTRIAL WASTE PICKLING LIQUORIn this journal, Abhisek, Anurag and Manindra explained thatin the last decade there is an upward trend for the global demand of zinc dueto increase in number of galvanizing lines and battery production linesworldwide, and the ore reserves for zinc are depleting gradually contributingto steep increase in cost of zinc.
To overcome the problem, zinc productionfrom secondary sources that have been increasing were explored, and the wastepickling liquor (WPL) generated during degalvanizing process is one of suchsecondary source of zinc that was researched. Methods such as below were used;1. Analysis of initial WPL Chemical analysis of WPL solution, before and afterprecipitation experiments, was done volumetrically by standard methods. The concentrations of zinc and iron were also determined byAtomic Absorption Spectroscopy (AAS) technique to recheck the chemical analysisresults.2. Precipitation experimentPerformed in two stages.
First stage, effect of varying thetemperature and stirring speed on Zn and Fe recovery efficiency was studied fora constant Zn ion. Second stage, effect of oxalic acid concentration and numberof reaction steps was examined at the precipitation conditions determined fromthe first stage experiment. All experiments in both stages were carried outusing 250mL WPL starting solution in standard lab glass beakers of 500mL.
Reaction time of 20 min was determined as optimum time for high zinc extractionefficiency with minimum iron extraction efficiency. 3. Characterization of precipitatesPrecipitates were dried at 110?C for 30min to removemoisture and characterized using X-ray diffraction (XRD). Results shows that Zinc recovery efficiency follows agradual increasing trend with increasing temperature and stirring speed. Figure 8 Effect of variation of oxalic acid concentrationand reaction steps on Zn and Fe Figure 9 XRD Pattern of Precipitates dried at 110?C Zinc is recovered with high efficiency from waste picklingliquor of galvanizing industry, by a two-step chemical precipitation methodusing oxalic acid as a precipitating agent. The optimum process parameters wereidentified as: temperature 25?C, stirring speed 100 rpm, and molar ration of Znion: oxalic acid = 1:1.4.
Efficiency of zinc recovery was estimated at 95%under optimized condition. The WPL after oxalic acid treatment can be reused aspickling liquor for more steel samples. This liquor with increased iron contentis consumed by iron oxide manufacturing industry to produce red oxide pigmentfor paint 8 This paper presents a wastewater treatment process andrecycling of iron sludge from wastewater treatment for iron oxide red production.Iron oxide red wastewater is a kind of typical acid wastewater. This wastewatercan decrease the pH of receiving waterbody leading to damage of growth ofaquatic organism. In addition, excess Fe2+ will change the appearance of water,and it can reduce the intensity of light and then hinder the photosynthesis ofaquatic plant.
The common way to treat this wastewater is alkalineneutralization. By adding alkali liquor and aerating, the Fe2+ can convert toFe3+ by oxidation and pH will increase, and increased pH results in greatquantity of brownish black sediment. Results shows that sludge from wastewater treatment processunder the operating parameters: 1.85 g/L of NaOH dosage, 10 mins of aerationwith flow rate of 1 L/min and 150 mins of sediment time is potential for seedcrystal preparation and excellent iron oxide red product can be obtained in thesecondary oxidation under condition of 85?C, 68h of reaction time and 150mL/min of airflow. Wastewater treatment jar test was experimented where thewastewater was taken into a beaker jar along with sodium hydroxide solution. Figure 10 pH effluent with different dosage of NaOH andaeration time.
The results based on Fig 9 is that, with the increase ofNaOH dosage, large amount of OH – was added to the wastewater, leading rinsingof primary pH of wastewater and effluent pH gradually increased after reactionof neutralization aeration, consuming certain amount of OH -. It can beconcluded by the 4 researches that not only wastewater was treated efficiently,but also sludge generating from the process was reused as the seed crystal toobtain excellent iron oxide red product. It is proved that the process iffeasible, economical and promising and cleaner production of iron oxide red canbe realized 10.
To obtain fine red powder of iron oxide, there are number ofimportant procedures to be followed correctly. From selecting raw materials,the type of equipment used and the precisions. The below steps would be a brief explanation on how thetesting should take place. Collect waste (Spent Pickle Liquor) from factory, (it isalready available in lab), ensure the waste is Hydrochloric Acid (HCL) with amixture of FeCl2 and H2O because those are what that makes up spent acid. It isimportant to check the density and specific gravity of the materials. Neutralize collected spent pickle liquor (SPL) with SodiumHydroxide (NaOH). The product of this neutralization would be Iron (II)Hydroxide, Sodium Chloride and Water.
While this neutralization process takesplace, the pH value should be monitored constantly to ensure the experiment tobe stopped when pH value reaches 8. Below is the neutralization processequation;FeCl2 + HCl + H2O + NaOH ? Fe (OH) 2 + NaCL + H2OWhen the FeCl2 volume varies, the volume of NaOH used variestoo. Therefore, constant monitoring on the variable is vital. After the neutralization process, Iron (II) Hydroxide,Sodium Chloride and Water are formed. To separate these compounds, a filtrationprocess will take place. The steps for filtration process would be:1.
Iron (II) Hydroxide will be the insoluble solid whereasSodium Chloride and Water will be the liquid in thebeaker. 2. These solution and solvent will be poured into a conicalflask through a filter paper.3. The filter paper filters out the Iron (II) Hydroxide(mixture).4.
The filtered liquid, or known as filtrate will be NaCland H2O. Now, the mixture, Iron (II) Hydroxide (Fe (OH) 2) will bedried either outside under hot sun or inside a lab drying oven at about 100 ?Cfor 3 to 4 hours until it is not like a wet slurry anymore. Dried mixture willbe blended using a blender until fine powder is achieved.
After it has dried, the residue will be placed in a volatileporcelain high temperature rectangular crucible that is available in the lab.Upon placing the dried (Fe (OH) 2) in a crucible, the crucible is then placedinside an Electric Furnace for Oxidation purpose. The dried mixture will becalcined for several hours in the porcelain crucible at 600 ?C 7. As thetemperature increases upon placing the crucible, the shading/color of the finepowder changes from red color to darker red. Now, after the oxidation, Iron(II) Hydroxide turns into Iron (III) Oxide (Fe2O3). After that process, theproducts will be sifted through a mesh screen. Figure 16 Electric Furnace, Crucible, and Mesh Screen Before placing the fine powder in a transparent packet, thepowder’s color should be checked using a Chroma meter. Chroma meter is a portable measurementinstrument designed to evaluate the color of objects.
Steps to use it issimple, press the ON button, point the circle screen on an object, and therewill be a data that appears on the screen. The data such as ‘L’ and ‘a’ valueneed to be searched in the lab color ball measurement . For example, if the ‘L’value shows +5, then it is L+ (White section, at the top section of thesphere). After collecting all the data and results, they should besent to Research Department (RD) at UPM to do XRD (X-Ray Diffraction) testing10. The scattering of X-rays by the regularly spaced atoms of acrystal, useful in obtaining information about the structure of the crystal.
After the neutralization process FeCl2 + HCl + H2O + NaOH ?Fe (OH) 2 + NaCL + H2O, the residue was dried in filter funnel to filtrate outthe water and sodium chloride leaving only Iron (II) Hydroxide as the residue.It was dried in the filter paper for 3 days under hot sun and the final productwas a rough powder which was dried in oven for 50 minutes at 100 ?C beforeblended into fine particle. The process explanation for the Figure 1 below areas follow: Blended Iron (II) Hydroxide was calcined at differenttemperatures in the furnace for oxidation purposes in order to obtain Iron(III) Oxide. Calcination of the powder took place at 6 different temperatures,they are 500?C, 600?C, 700?C, 800?C, 900?C and 1000?C at 1 hour with overnightof cooling down in furnace. Based on visual inspection, hematite phase can berecognized by its distinct red colour 1 for calcination at 500, 600 and 700degree Celsius. The specimen was identified with X-ray diffraction using CuK? radiation ranging from drive axis of Theta-2Theta, scan range 20? to 80? ata scanning rate of 4?/min. Figure below shows the X-ray Diffraction patterns ofthe Iron (II) Hydroxide before being calcined in the furnace.
The superfine Fe2O3 powders were successfully prepared andsynthesized by neutralizing spent acid with sodium hydroxide and final productof red iron oxide pigment (hematite) was obtained. The temperature has a veryimportant influence on synthesis, and in this experiment, calcination at(700?C, 1 hour in furnace and 24 hours of cooling down in furnace) gives abrighter red colour Iron (III) Oxide powder compared to oxidation at othertemperatures. As for the Chroma meter reading, it was observed that the higherthe calcination temperature, the lower the L*a*b* values (darker colour, almostdark maroon-purplish towards 1000?C of oxidation in furnace). This study has proven that it is possible to convert rawspent pickling waste into colour pigment with fine particle size. The presenceof hematite observed via visual inspection (red colour) in the iron oxidepowder allows conversion into red colour pigment which can be used for tiles.
This results suggest that this is a simple, cheap and effective and also fastroute on preparing for a bright red hematite for usage on tiles. It is recommended that when preparing 30g of sample duringneutralization, alkali solution should mix with the acid drop by drop as eachdrop gives different pH value for the acid, and when the alkali drop exceedsfor instance from 25 to 27, the pH meter will hike up from 5 to 9 all of asudden, therefore, extra precaution should be taken from drop 20 onwards,suggesting half drop until achieving pH value of 8.5 would be safer. Besides that,it is also better if all three samples prepared have almost the same or closervalue of pH to ensure it does not affect the colour intensity later.