Thanks Nuchaz
it worked.
I had to replace some parameters on the addVertexWithUV, as the previous code was calculating the particle coordinates within the particles.png sheet, and binding a single texture wouldn't need that.
I'm showing the code for others to profit:
@Override
public void renderParticle(Tessellator par1Tessellator, float par2, float par3, float par4, float par5, float par6, float par7)
{
//func_98187_b() = bindTexture();
FMLClientHandler.instance().getClient().renderEngine.func_98187_b("/mods/mocreatures/textures/misc/FXvanish.png");
float scale = 0.1F * this.particleScale;
float xPos = (float) (this.prevPosX + (this.posX - this.prevPosX) * (double) par2 - interpPosX);
float yPos = (float) (this.prevPosY + (this.posY - this.prevPosY) * (double) par2 - interpPosY);
float zPos = (float) (this.prevPosZ + (this.posZ - this.prevPosZ) * (double) par2 - interpPosZ);
float colorIntensity = 1.0F;
par1Tessellator.setColorOpaque_F(this.particleRed * colorIntensity, this.particleGreen * colorIntensity, this.particleBlue * colorIntensity);//, 1.0F);
par1Tessellator.addVertexWithUV((double) (xPos - par3 * scale - par6 * scale), (double) (yPos - par4 * scale), (double) (zPos - par5 * scale - par7 * scale), 0D, 1D);
par1Tessellator.addVertexWithUV((double) (xPos - par3 * scale + par6 * scale), (double) (yPos + par4 * scale), (double) (zPos - par5 * scale + par7 * scale), 1D, 1D);
par1Tessellator.addVertexWithUV((double) (xPos + par3 * scale + par6 * scale), (double) (yPos + par4 * scale), (double) (zPos + par5 * scale + par7 * scale), 1D, 0D);
par1Tessellator.addVertexWithUV((double) (xPos + par3 * scale - par6 * scale), (double) (yPos - par4 * scale), (double) (zPos + par5 * scale - par7 * scale), 0D, 0D);
}