Remove duplicated posts in the loop if post has more than one category

Question

I have some posts with more than one category. In the post loop i get the post based on the selected category by the user. If the user select 2 categories where one post is assigned to, the loop duplicate the post. I tried to use array_unique() but doesn't work.

Here is my code:

  <?php
    global $current_user;
        get_currentuserinfo();



     //$current_user->user_categories;

     $ucategory = maybe_unserialize($current_user->user_categories);

     foreach ($ucategory as $category) {



    $query = new WP_Query( array( 'post_type' => array( 'service'),
                                   'category__in' => array($category)));





    $i=0;
    while ( $query->have_posts() ) : $query->the_post();

     if ($i%3==0) echo '



        ';

          echo '

                <div class="col-md-4 ">

                    <div class="col-md-12 service-cell">            
                <a href="'; the_permalink(); echo '">';
          echo the_post_thumbnail('thumbnail', array('class' => 'app-icon'));      
          echo '<h2 class="center">'; the_title(); echo '</h2></a>';

                foreach((get_the_category()) as $childcat) {
                if (cat_is_ancestor_of(3, $childcat)) {
                echo '<h3 class="sub">';
                echo $childcat->cat_name . '</h3>';
                }}     


                echo '<p>';
                echo excerpt(25);
                echo '<p><a href="'; the_permalink(); echo '">'; echo 'Wijzig uw gegevens</a>
                  <a class="pull-right"><span class="label label-default"><span class="glyphicon glyphicon-ok"></span></span></a></p>';
                echo '</p>';


          echo '';

              echo '</div></div>';


        if ($i%3==2) echo ''; 
        $i++;
    endwhile;

    }
?>