Atık Fe-Mo-Co ferro alaşımının liç kinetiği ve ürün kazanımı
Waste Fe-Mo-Co ferro alloy leach ki̇neti̇c and product recovery
Yazar: ARAS KARTUN
Danışman: PROF. DR. MAHMUT ERCAN AÇMA
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Metalurji ve Malzeme Mühendisliği Ana Bilim Dalı / Malzeme Bilimi ve Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2016
Konu: Metalurji Mühendisliği = Metallurgical Engineering

Özet:
Ferromolibden alaşımları günümüzde çelik üretimi için çok önemlidir. Çelik üretimi
sırasında ferromolibden alaşımı ilavesiyle molibden çelik yapısına katılabilmektedir.
Hatta saf molibden ilavesine göre çelik içerisine ferromolibden katılması, çok daha
kolay çözünme sağladığından çoğu tesiste tercih edilmektedir. Kobalt da aynı
molibden gibi alaşımlamada sıklıkla kullanılmaktadır.
Kobaltı da yapısında bulunduran ferromolibden alaşımlarının üretimi sırasında
önemli miktarlarda atık alaşımlar oluşabilmektedir. Bu atık alaşımların tekrar
değerlendirilmesi ve içeriğinde bulunan metallerin ticari ürünler halinde kazanılması
günümüz metal sektörü için önemli bir konudur. Bu tez çalışmasının amacı da atık
haldeki demir, kobalt, molibden içeren ferro alaşımın hidrometalurjik yöntemle
çözeltiye alınmasının ve bu metallerin her birinin ticari ürünlere dönüştürme
deneylerinin incelenmesidir.
Çevreci bir metalurjik üretim yöntemi olan hidrometalurjik üretim yöntemi deneyler
boyunca kullanılmıştır.
Deneyler, 100 ml'lik balonjojeler içerisinde, su ile ısıtmalı bir sistemle
gerçekleştirilmiştir. Deneylerde çözeltiye almak için H2SO4 ve HNO3 asitleri
kullanılarak, oksitleyici etkisi, sülfürik asit konsantrasyonu, karıştırma hızı, katı-sıvı
oranı, çözümlendirme süresi ve sıcaklığı parametreleri incelenmiştir. Sıcaklık ve
zaman bazlı deneyler sonucu liç kinetiği ortaya çıkarılmıştır. Bileşimde bulunan üç
ana metalin de çözeltiye alınması için gerekli tepkimelerdeki aktivasyon enerjileri
hesaplanmıştır. Yapılan hesaplamalarda, 33,36 kJ, 19,51 kJ ve 25,62 kJ aktivasyon
enerjileri bulunmuştur. Çözünme mekanizmasının difüzyon kontrollü olduğu ortaya
konulmuştur. Jander Üç Boyutlu Model'i tek tek üç metale de uygulanmış, bulunan
değerlerden yapılan yorumla modelin difüzyon kontrollü mekanizmaya uyduğu
kanıtlanmıştır.
Çözünme gerçekleştirildikten sonra elde edilen, çözünen üç ana metali barındıran
çözeltilerden uygun proses şartlarında, ticari safiyette MoS3, Fe2O3, Co(OH)2
kimyasalları elde edilmiştir.

Abstract:
In our day, ferromolybdenum alloys are quite important for steel production. By
ferromolybdenum addition during the steel production, molybdenum can join in steel
structure. So that it's preferred by many facilities to add ferromolybdenum into the
steel instead of pure molybdenum due to the fact that it ensures much more easy
dissolution. Also cobalt can join in structures as an alloy element.
The waste alloys can be formed, after produce ferro alloys which contain cobalt.
Assesment of waste alloys and recycling metals as commercially pure compound is
an important issue for metal industry. The aim of this project is to investigate
dissolution of waste ferromolybdenum alloy which contain cobalt by
hydrometallurgical process and recovery of each three metals as commercially pure
compounds.
The hydrometallurgical production method used throughout the experiments which is
known to be an environmentalist way.
Experiments were carried out in volumetric flasks within a water heated system. In
the experiments, H2SO4 and HNO3 were used for solution treat, and oxidizing effect,
sulphuric acid concentration, stirring speed, solid-liquid ratio, dissolution time and
temperature parameters were investigated. Leaching kinetics were undisclosed in
consequence of temperature and time based experiments. Activation energies for all
three metals in compound to be treated into solution were found. By calculations,
activation energies were found as 33,36 kJ/mol, 19,51 kJ/mol and 25,62 kJ/mol. It's
stated that dissolution mechanism is diffusion controlled.
Jander 3 Dimensional Diffusion Model was applied to all three metals, based on
found values, it's proved that the process is diffusion controlled.
After the dissolution, all of these three main metals were obtained commercially pure
as MoS3, Fe2O3 and Co(OH)2 under the appropriate process conditions.
There are three methods applied in metal production: pyrometallurgy,
hydrometallurgy and electrometallurgy. Hydrometallurgy is the most preferred metal
production method due to its affordability, ability to utilize low-tenor ores, quality to
help the high-purity recycling of seperate metals in a synchronous way, homogenious
nature of its reactions in aqueous medium and controllability.
Hydrometallurgic production begins with making the leching in an acidic or alkaline
iye. The iye which includes metal, is seperated from leaching remnant. Lastly, with
the use of various methods the metal compound is obtained. After the metals are
solubilized they are recovered by being selective. First, the leaching solution is
needed to be purified and enriched. Metal recovery, precipitation or electrolytic
methods are realized.
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The advantages of this method are its frequent use to obtain metal from complex ores
and its feasibilty to process residue, waste byproducts from oxidised and oxysulphide
combined ores. And the disadvantages are the remaining of valuable materials in a
waste solution after leaching process and the insufficient amount of leach on a mass
per unit basis in especially large scale solutions. Leahing process is a total of
heterogeneous reactions. While this heterogeneousity is between the different states
of matter, generally the reactions take place in solid and liquid states.
To understand a chemical reaction, the reaction must beanalysed from both
termodynamic and kinetic perspective. From a general point of view, termodynamics
analyses whether a rection will take place or not. On the other hand, kinetics looks at
the speed of the reaction and the factors affecting it. Kinetics is interested in the mass
change inthe unit of time.
To understand the reaction speed in especially solid-liquid reactions, resolution
systematics must be analysed during heterogeneous reactions. In solid-liquid
reactions, the surrounding of the solid is wrapped with stagnant liquid film. The
materialisation of the reaction depends on the reactant's reaching to interface layer,
diffused from film surface. This film layer is formed because the liquid sticks to the
layer, holds on there and has viscosity. If the reactant can be diffused from film
layer, it will reach to interface surface. This interface surface is known as Nerst
Boundary Surface.
The processing of the reaction is controlled by a certain phenomenon. Speed control
can be a diffused or chemical reaction based on different parameters and features.
While the reaction takes place in the interface, either chemical reaction or diffusion
materialises faster. Based on how fast this takes place the mechanism which will
control the reaction. If the chemical reaction taking place in the interface gets faster
than the reactant which is diffused to the interface, the materialised process is named
as diffusion controlled. If vice versa happens and the diffusion takes place faster,
process is named as chemical controlled.
The mechanism which will control the reaction shows change according to different
factors. The basic determining parameters are fluid speed, temprature, reactant
concentration.
Through estimating activation energy, looking at the change of the reaction based on
certain parameters, diffusion controlled reactions can be interpreted. However, there
are many models in the literature putting forward the mechanism of the reaction. One
of them is designed by Jander in 1927. It is a three dimensional model, based on
core model.
If reaction is diffusion controlled during solid state reactions, this model is often used
for putting forward the reaction mechanism. This model is set forth with the help of
parabolic speed evenness.
Precipitation process is the last step of metallurgic process. Metals can be
precipitated through many different ways.
The ionic precipitation method is done through adding a non-ionic factor to the
solution and producing metal composites in a selective way. The resolution of the
solutions made through this method is low but the creation speed is high.
Materialised reactions may include hydrolysis rections.
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The precipitation of metal composites is possible through electron transaction. Thim
method is known as degraded precipitation. The metal which will be precipitated is
degraded by a degrader to a lower load. At the same time, it is surely oxidised.
In electrochemical precipitation method, yönteminde ise, a more noble metal is used
for precipitating a more noble metal. To compare nobility, electrochemical potentials
are used. With the help of electrochemical potentials, precipitating a metal in another
metal solution becomes a possibility.
Taking advantage of hydrogen's asility to act sometimes as metal, sometimes as nonmetal,
it is often used in substitution reactions. Thanks to that, it plays a huge rol in
producing metals through precipitation. By substituting hydrogen with copper,
hydrogen with nickels, this metals can be produced.
Aqueous solution can produce its own metal, if only an outer electromotor force is
passed from the right source of current. This method is called electrolytic
precipitation.
The time and temprature experiments to determine leaching kinetics are executed
with 100 milliliter volumetric flasks. In this volumetric flasks nitric acid and
sulpuric acid concentrations are practiced together and in order to make heating
homogeneous the glass with water in it is heated and volumteric flasks have reached
certain temprature. During the experiment oxidising effect, sulphuric acid
concentration effect, mixing speed effect, solid-aquatic ratio, mixing speed, resolving
time and tempreature are analysed. The experiments to determine leaching's
optimum conditions were practiced with 50 mililiter solutions.
Settling test are performed to realise the commercial recovery of the metals which
are taken into the solution in optimum conditions. By using previous experiment
outputs, 500 mililiters of solution in optimum conditions are prepared. For this
experiments, a total 100 grams of ferromolibden powder was seperated into 10 grams
and leached for 10 times. Through this, metals in ferromolibden powder were
degraded.
First, to recover the molibden in prepared solution, H2S gas was produced and this
gas was passed from the solution. For this, powder FeS, including %29 of S, and 1/1
H2SO4 were reacted together with kipps apparatus. At the end, H2S gas was produced
and this gas was passed from the solution. After all this process, MoS3, which has a
commercal value in its ph volüme one. To equalise pH in the experiments, 5 M
NaOH was used.
Second, to produce a resoluted iron and transform the Fe+2 ions in the solution to
Fe+3, %35 oxidised H2O2 was used. Until it has become pH 3, 5 M NaOH addition
was the case. With this, alongside the increasing time, iron ions were precipitated.
The sediments which were filtered with filtter paper, were processed in the oven at
700°C and it is deprived of H2O in its structure while leaving the way to the
production of Fe2O3 having commercial value.
Lastly, cobalt, which is a basic element, was brought to pH 9 with NaOH addtion at
60°C and was precipitated as Co(OH)2